Re: A neat and compact way to generate RF harmonics...

[Paul Burridge]

On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> wrote:


> Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
>better.
> And they are a *LOT* smaller!

Thanks, Robert (and all else)
I'd prefer a diode solution as there'd be no power supply requirements
for each device. The tiny size is an added bonus, of course. But
what's the drawback with superfast switching diodes as against active
inverters? I'm sure there must be (at least) one...

[Paul Burridge]

On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> wrote:


> Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
>better.
> And they are a *LOT* smaller!

Thanks, Robert (and all else)
I'd prefer a diode solution as there'd be no power supply requirements
for each device. The tiny size is an added bonus, of course. But
what's the drawback with superfast switching diodes as against active
inverters? I'm sure there must be (at least) one...

[Harold E. Johnson]

> I'd prefer a diode solution as there'd be no power supply requirements
> for each device. The tiny size is an added bonus, of course. But
> what's the drawback with superfast switching diodes as against active
> inverters? I'm sure there must be (at least) one...
>
Well for starters, they often, (VERY often) act as parametric devices and
oscillate on their own at the frequency of their choosing.

W4ZCB

[Harold E. Johnson]

> I'd prefer a diode solution as there'd be no power supply requirements
> for each device. The tiny size is an added bonus, of course. But
> what's the drawback with superfast switching diodes as against active
> inverters? I'm sure there must be (at least) one...
>
Well for starters, they often, (VERY often) act as parametric devices and
oscillate on their own at the frequency of their choosing.

W4ZCB

[Robert Baer]

Paul Burridge wrote:
>
> On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> > wrote:
>
> > Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
> >better.
> > And they are a *LOT* smaller!
>
> Thanks, Robert (and all else)
> I'd prefer a diode solution as there'd be no power supply requirements
> for each device. The tiny size is an added bonus, of course. But
> what's the drawback with superfast switching diodes as against active
> inverters? I'm sure there must be (at least) one...

An active inverter is S L O W by comparison; a good, fast diode can
have turnoff times in the tens of picoseconds region.

[Robert Baer]

Paul Burridge wrote:
>
> On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> > wrote:
>
> > Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
> >better.
> > And they are a *LOT* smaller!
>
> Thanks, Robert (and all else)
> I'd prefer a diode solution as there'd be no power supply requirements
> for each device. The tiny size is an added bonus, of course. But
> what's the drawback with superfast switching diodes as against active
> inverters? I'm sure there must be (at least) one...

An active inverter is S L O W by comparison; a good, fast diode can
have turnoff times in the tens of picoseconds region.

[Fred Bartoli]

"Robert Baer" > a écrit dans le message news:
...
> Paul Burridge wrote:
> >
> > On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> > > wrote:
> >
> > > Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
> > >better.
> > > And they are a *LOT* smaller!
> >
> > Thanks, Robert (and all else)
> > I'd prefer a diode solution as there'd be no power supply requirements
> > for each device. The tiny size is an added bonus, of course. But
> > what's the drawback with superfast switching diodes as against active
> > inverters? I'm sure there must be (at least) one...
>
> An active inverter is S L O W by comparison; a good, fast diode can
> have turnoff times in the tens of picoseconds region.


Don't let Paul dream too much about picoseconds.
In order to achieve results that good, one have to pay very careful
attention to "wiring". There's still a lot of room for Paul to improve his
PCB design skills ;-)

Thanks,
Fred.

[Fred Bartoli]

"Robert Baer" > a écrit dans le message news:
...
> Paul Burridge wrote:
> >
> > On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
> > > wrote:
> >
> > > Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
> > >better.
> > > And they are a *LOT* smaller!
> >
> > Thanks, Robert (and all else)
> > I'd prefer a diode solution as there'd be no power supply requirements
> > for each device. The tiny size is an added bonus, of course. But
> > what's the drawback with superfast switching diodes as against active
> > inverters? I'm sure there must be (at least) one...
>
> An active inverter is S L O W by comparison; a good, fast diode can
> have turnoff times in the tens of picoseconds region.


Don't let Paul dream too much about picoseconds.
In order to achieve results that good, one have to pay very careful
attention to "wiring". There's still a lot of room for Paul to improve his
PCB design skills ;-)

Thanks,
Fred.

[Paul Burridge]

On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
_AndThisToo> wrote:

>Don't let Paul dream too much about picoseconds.

Well, quite. I wouldn't know what to do with all those extra
harmonics, anyway. :-)
Diodes sound great, but I'm heavily put off by that comment earlier in
the thread that they're prone to self oscillation. :-( What's a
"parametric device" anyway?

>In order to achieve results that good, one have to pay very careful
>attention to "wiring". There's still a lot of room for Paul to improve his
>PCB design skills ;-)

Fair comment. But I *am* working on it!

[Paul Burridge]

On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
_AndThisToo> wrote:

>Don't let Paul dream too much about picoseconds.

Well, quite. I wouldn't know what to do with all those extra
harmonics, anyway. :-)
Diodes sound great, but I'm heavily put off by that comment earlier in
the thread that they're prone to self oscillation. :-( What's a
"parametric device" anyway?

>In order to achieve results that good, one have to pay very careful
>attention to "wiring". There's still a lot of room for Paul to improve his
>PCB design skills ;-)

Fair comment. But I *am* working on it!

[Leon Heller]

"Paul Burridge" > wrote in message
...
> On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
> _AndThisToo> wrote:
>
> >Don't let Paul dream too much about picoseconds.
>
> Well, quite. I wouldn't know what to do with all those extra
> harmonics, anyway. :-)
> Diodes sound great, but I'm heavily put off by that comment earlier in
> the thread that they're prone to self oscillation. :-( What's a
> "parametric device" anyway?

Parametric operation is when you have a parameter such as diode capacitance
that varies with voltage. The non-linearity of the parameter makes it act as
a multiplier, mixer or an amplifier. Parametric amplifiers (they need to be
'pumped' with an oscilllator) used to be very popular for microwave use. If
you have inadvertently make yourself a parametric amplifier with your diode
it could oscillate given the right conditions and do all sorts of strange
things. In your hands, this is a strong possibility. 8-)

Leon

[Leon Heller]

"Paul Burridge" > wrote in message
...
> On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
> _AndThisToo> wrote:
>
> >Don't let Paul dream too much about picoseconds.
>
> Well, quite. I wouldn't know what to do with all those extra
> harmonics, anyway. :-)
> Diodes sound great, but I'm heavily put off by that comment earlier in
> the thread that they're prone to self oscillation. :-( What's a
> "parametric device" anyway?

Parametric operation is when you have a parameter such as diode capacitance
that varies with voltage. The non-linearity of the parameter makes it act as
a multiplier, mixer or an amplifier. Parametric amplifiers (they need to be
'pumped' with an oscilllator) used to be very popular for microwave use. If
you have inadvertently make yourself a parametric amplifier with your diode
it could oscillate given the right conditions and do all sorts of strange
things. In your hands, this is a strong possibility. 8-)

Leon

[Harold E. Johnson]

> Parametric operation is when you have a parameter such as diode
capacitance
> that varies with voltage. The non-linearity of the parameter makes it act
as
> a multiplier, mixer or an amplifier. Parametric amplifiers (they need to
be
> 'pumped' with an oscilllator) used to be very popular for microwave use.
If
> you have inadvertently make yourself a parametric amplifier with your
diode
> it could oscillate given the right conditions and do all sorts of strange
> things. In your hands, this is a strong possibility. 8-)
>

I think you have a point Leon. Paul, use a Schottky diode, (HP 5082-2835 or
similar), use ZERO lead lengths. Make your PCBoard for the multiplier double
sided, drill a hole the diameter of the diode length, wrap a copper tape
ground from top to bottom on one edge of the hole, and drop the diode in the
hole and solder both ends. One end to the ground tape, the other to the land
to the filter for the harmonic you want. Then, drive with not more than +10
dBm of fundamental and hope a lot. It may STILL oscillate, but you've
maximized your chances. When you start getting output from the filter (on
the desired frequency which ought to be the only output you can get with the
filter in place) you can start matching the input to the diode with "L"
networks to maximize the output. Generally, the diode looks like a quite low
impedance so the capacitor used, ought to wind up on the side of the
inductor AWAY from the diode.

You can use an MMIC in the same manner to generate harmonics. Overdrive it
and under feed it with DC. More output, more chance of self oscillation if
you don't pay attention to detail.

A superior (less touchy) method of harmonic generation is just a full wave
diode rectifier. Using signal diodes and a center tapped transformer, make a
full wave doubler. Ground the DC out with an RF choke and you have 2F the
input frequency with good suppression of the fundamental and odd harmonics
built in. It's then a lot easier to filter the rest of the undesired out. Do
two of those to get 4F out rather than trying to do it all in one stage.
LOTS more efficiency.

W4ZCB

[Harold E. Johnson]

> Parametric operation is when you have a parameter such as diode
capacitance
> that varies with voltage. The non-linearity of the parameter makes it act
as
> a multiplier, mixer or an amplifier. Parametric amplifiers (they need to
be
> 'pumped' with an oscilllator) used to be very popular for microwave use.
If
> you have inadvertently make yourself a parametric amplifier with your
diode
> it could oscillate given the right conditions and do all sorts of strange
> things. In your hands, this is a strong possibility. 8-)
>

I think you have a point Leon. Paul, use a Schottky diode, (HP 5082-2835 or
similar), use ZERO lead lengths. Make your PCBoard for the multiplier double
sided, drill a hole the diameter of the diode length, wrap a copper tape
ground from top to bottom on one edge of the hole, and drop the diode in the
hole and solder both ends. One end to the ground tape, the other to the land
to the filter for the harmonic you want. Then, drive with not more than +10
dBm of fundamental and hope a lot. It may STILL oscillate, but you've
maximized your chances. When you start getting output from the filter (on
the desired frequency which ought to be the only output you can get with the
filter in place) you can start matching the input to the diode with "L"
networks to maximize the output. Generally, the diode looks like a quite low
impedance so the capacitor used, ought to wind up on the side of the
inductor AWAY from the diode.

You can use an MMIC in the same manner to generate harmonics. Overdrive it
and under feed it with DC. More output, more chance of self oscillation if
you don't pay attention to detail.

A superior (less touchy) method of harmonic generation is just a full wave
diode rectifier. Using signal diodes and a center tapped transformer, make a
full wave doubler. Ground the DC out with an RF choke and you have 2F the
input frequency with good suppression of the fundamental and odd harmonics
built in. It's then a lot easier to filter the rest of the undesired out. Do
two of those to get 4F out rather than trying to do it all in one stage.
LOTS more efficiency.

W4ZCB

[Tom Bruhns]

If I understand correctly, you're interested in harmonics up in the
70MHz region. To me it seems silly to use diodes capable of
generating a comb of harmonics out to 20GHz for that. An advantage--a
big advantage--of the tiny logic is that you get considerable power
gain in the stage, and the sot-23 package is likely no larger than the
diode you might have used anyway. The edges, as others have pointed
out, are PLENTY fast enough for what I believe you want to do.

Whether you use diodes or gates, your size problem will be the
harmonic-selection filter. As you've learned (and I trust not
forgotten already), you need either multiple poles in your filter or a
rather high Q. You _could_ get the high Q with crystals, but of
course then you're locked down to particular frequencies. For high
multiplication factors to low-VHF frequencies, it's probably hard to
beat a PLL for (potentially) small size.

In offering suggestions, it would also be helpful to us to know your
actual needs for signal purity, both close-in (phase noise) and
broadband (other harmonics, etc.)

If you do use diodes for higher-order harmonic generation, and not
just a simple full-wave-rectifier type frequency doubler, I suppose
you want something of the nature of a step recovery diode. That
implies minority carrier stored charge in the diode, and that would
preclude using a Schottky diode (which would work great in the
full-wave-rectifier type doubler). If you get into actually wanting
to generate harmonic combs out to microwave frequencies, it's probably
worthwhile looking for diodes actually characterized for step recovery
service. But I really think that's way beyond what you are trying to
accomplish right now.

Cheers,
Tom


Paul Burridge > wrote in message >...
> On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
> _AndThisToo> wrote:
>
> >Don't let Paul dream too much about picoseconds.
>
> Well, quite. I wouldn't know what to do with all those extra
> harmonics, anyway. :-)
> Diodes sound great, but I'm heavily put off by that comment earlier in
> the thread that they're prone to self oscillation. :-( What's a
> "parametric device" anyway?
>
> >In order to achieve results that good, one have to pay very careful
> >attention to "wiring". There's still a lot of room for Paul to improve his
> >PCB design skills ;-)
>
> Fair comment. But I *am* working on it!

[Tom Bruhns]

If I understand correctly, you're interested in harmonics up in the
70MHz region. To me it seems silly to use diodes capable of
generating a comb of harmonics out to 20GHz for that. An advantage--a
big advantage--of the tiny logic is that you get considerable power
gain in the stage, and the sot-23 package is likely no larger than the
diode you might have used anyway. The edges, as others have pointed
out, are PLENTY fast enough for what I believe you want to do.

Whether you use diodes or gates, your size problem will be the
harmonic-selection filter. As you've learned (and I trust not
forgotten already), you need either multiple poles in your filter or a
rather high Q. You _could_ get the high Q with crystals, but of
course then you're locked down to particular frequencies. For high
multiplication factors to low-VHF frequencies, it's probably hard to
beat a PLL for (potentially) small size.

In offering suggestions, it would also be helpful to us to know your
actual needs for signal purity, both close-in (phase noise) and
broadband (other harmonics, etc.)

If you do use diodes for higher-order harmonic generation, and not
just a simple full-wave-rectifier type frequency doubler, I suppose
you want something of the nature of a step recovery diode. That
implies minority carrier stored charge in the diode, and that would
preclude using a Schottky diode (which would work great in the
full-wave-rectifier type doubler). If you get into actually wanting
to generate harmonic combs out to microwave frequencies, it's probably
worthwhile looking for diodes actually characterized for step recovery
service. But I really think that's way beyond what you are trying to
accomplish right now.

Cheers,
Tom


Paul Burridge > wrote in message >...
> On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
> _AndThisToo> wrote:
>
> >Don't let Paul dream too much about picoseconds.
>
> Well, quite. I wouldn't know what to do with all those extra
> harmonics, anyway. :-)
> Diodes sound great, but I'm heavily put off by that comment earlier in
> the thread that they're prone to self oscillation. :-( What's a
> "parametric device" anyway?
>
> >In order to achieve results that good, one have to pay very careful
> >attention to "wiring". There's still a lot of room for Paul to improve his
> >PCB design skills ;-)
>
> Fair comment. But I *am* working on it!

[Harold E. Johnson]

> If you do use diodes for higher-order harmonic generation, and not
> just a simple full-wave-rectifier type frequency doubler, I suppose
> you want something of the nature of a step recovery diode. That
> implies minority carrier stored charge in the diode, and that would
> preclude using a Schottky diode (which would work great in the
> full-wave-rectifier type doubler). If you get into actually wanting
> to generate harmonic combs out to microwave frequencies, it's probably
> worthwhile looking for diodes actually characterized for step recovery
> service. But I really think that's way beyond what you are trying to
> accomplish right now.

My turn to learn something here. Tom, would you elaborate a bit on the above
please? I know SRD's are comb generators out to visible light, but they're
also 50 percent hard to find and 50 percent magic. I've been using
Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
promising myself that I'm gonna substitute an MMIC for that one day, I DID
find the "Filter Gain" in the line length from generator to filter), THAT
was both impressive AND helpful. If I go with the MMIC, any preference of
Silicon over GaAs?

Regards

W4ZCB

[Harold E. Johnson]

> If you do use diodes for higher-order harmonic generation, and not
> just a simple full-wave-rectifier type frequency doubler, I suppose
> you want something of the nature of a step recovery diode. That
> implies minority carrier stored charge in the diode, and that would
> preclude using a Schottky diode (which would work great in the
> full-wave-rectifier type doubler). If you get into actually wanting
> to generate harmonic combs out to microwave frequencies, it's probably
> worthwhile looking for diodes actually characterized for step recovery
> service. But I really think that's way beyond what you are trying to
> accomplish right now.

My turn to learn something here. Tom, would you elaborate a bit on the above
please? I know SRD's are comb generators out to visible light, but they're
also 50 percent hard to find and 50 percent magic. I've been using
Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
promising myself that I'm gonna substitute an MMIC for that one day, I DID
find the "Filter Gain" in the line length from generator to filter), THAT
was both impressive AND helpful. If I go with the MMIC, any preference of
Silicon over GaAs?

Regards

W4ZCB

[John Larkin]

On Mon, 12 Apr 2004 19:09:51 GMT, "Harold E. Johnson"
> wrote:

>
>> If you do use diodes for higher-order harmonic generation, and not
>> just a simple full-wave-rectifier type frequency doubler, I suppose
>> you want something of the nature of a step recovery diode. That
>> implies minority carrier stored charge in the diode, and that would
>> preclude using a Schottky diode (which would work great in the
>> full-wave-rectifier type doubler). If you get into actually wanting
>> to generate harmonic combs out to microwave frequencies, it's probably
>> worthwhile looking for diodes actually characterized for step recovery
>> service. But I really think that's way beyond what you are trying to
>> accomplish right now.
>
>My turn to learn something here. Tom, would you elaborate a bit on the above
>please? I know SRD's are comb generators out to visible light, but they're
>also 50 percent hard to find and 50 percent magic. I've been using
>Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
>promising myself that I'm gonna substitute an MMIC for that one day, I DID
>find the "Filter Gain" in the line length from generator to filter), THAT
>was both impressive AND helpful. If I go with the MMIC, any preference of
>Silicon over GaAs?
>
>Regards
>
>W4ZCB
>

The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

John

[John Larkin]

On Mon, 12 Apr 2004 19:09:51 GMT, "Harold E. Johnson"
> wrote:

>
>> If you do use diodes for higher-order harmonic generation, and not
>> just a simple full-wave-rectifier type frequency doubler, I suppose
>> you want something of the nature of a step recovery diode. That
>> implies minority carrier stored charge in the diode, and that would
>> preclude using a Schottky diode (which would work great in the
>> full-wave-rectifier type doubler). If you get into actually wanting
>> to generate harmonic combs out to microwave frequencies, it's probably
>> worthwhile looking for diodes actually characterized for step recovery
>> service. But I really think that's way beyond what you are trying to
>> accomplish right now.
>
>My turn to learn something here. Tom, would you elaborate a bit on the above
>please? I know SRD's are comb generators out to visible light, but they're
>also 50 percent hard to find and 50 percent magic. I've been using
>Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
>promising myself that I'm gonna substitute an MMIC for that one day, I DID
>find the "Filter Gain" in the line length from generator to filter), THAT
>was both impressive AND helpful. If I go with the MMIC, any preference of
>Silicon over GaAs?
>
>Regards
>
>W4ZCB
>

The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

John

[Harold E. Johnson]

>
> The only distributor-stock SRDs I know of are the M/Acom MA44767,
> MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
> carries them. The '68 or '69 should be good for multiplication to 2
> GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
> There are lots of appnotes around about using them as multipliers.
>
> I have a bunch in stock and can send a few to anybody who wants to
> play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

[Harold E. Johnson]

>
> The only distributor-stock SRDs I know of are the M/Acom MA44767,
> MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
> carries them. The '68 or '69 should be good for multiplication to 2
> GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
> There are lots of appnotes around about using them as multipliers.
>
> I have a bunch in stock and can send a few to anybody who wants to
> play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

[John Larkin]

On Mon, 12 Apr 2004 22:16:01 GMT, "Harold E. Johnson"
> wrote:

>
>
>>
>> The only distributor-stock SRDs I know of are the M/Acom MA44767,
>> MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>> carries them. The '68 or '69 should be good for multiplication to 2
>> GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>> There are lots of appnotes around about using them as multipliers.
>>
>> I have a bunch in stock and can send a few to anybody who wants to
>> play.
>
>I'd like to talk you out of a couple, and thanks for the supplier info.
>Wonder what MaCom's min order is? Anything you need in trade or a few green
>stamps?
>
>W4ZCB
>Call Book Address.
>
^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

John

[John Larkin]

On Mon, 12 Apr 2004 22:16:01 GMT, "Harold E. Johnson"
> wrote:

>
>
>>
>> The only distributor-stock SRDs I know of are the M/Acom MA44767,
>> MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>> carries them. The '68 or '69 should be good for multiplication to 2
>> GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>> There are lots of appnotes around about using them as multipliers.
>>
>> I have a bunch in stock and can send a few to anybody who wants to
>> play.
>
>I'd like to talk you out of a couple, and thanks for the supplier info.
>Wonder what MaCom's min order is? Anything you need in trade or a few green
>stamps?
>
>W4ZCB
>Call Book Address.
>
^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

John

[Paul_Morphy]

"John Larkin" > wrote in
message ...

> >
> >W4ZCB
> >Call Book Address.
> >
> ^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
> despam.

http://qrz.com/callsign/w4zcb

"PM"

[Paul_Morphy]

"John Larkin" > wrote in
message ...

> >
> >W4ZCB
> >Call Book Address.
> >
> ^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
> despam.

http://qrz.com/callsign/w4zcb

"PM"

[Tom Bruhns]

Hi Harold,

Nice of John to make that offer!

As for background and theory, I'll make copies of an artcile or two to
send you, about the discovery of the effect and the optimization of
diode structure to enhance it. I suppose that the effect you're
seeing with the Schottkys is almost entirely capacitive stored charge,
and that won't "sweep out" of the diode with the sharp step you get
with a step-recovery diode. The articles I'll send have info about
efficiency, which can be surprisingly high considering the high order
of multiplication.

Cheers,
Tom

"Harold E. Johnson" > wrote in message news:<3QBec.21137$_K3.55643@attbi_s53>...
> > If you do use diodes for higher-order harmonic generation, and not
> > just a simple full-wave-rectifier type frequency doubler, I suppose
> > you want something of the nature of a step recovery diode. That
> > implies minority carrier stored charge in the diode, and that would
> > preclude using a Schottky diode (which would work great in the
> > full-wave-rectifier type doubler). If you get into actually wanting
> > to generate harmonic combs out to microwave frequencies, it's probably
> > worthwhile looking for diodes actually characterized for step recovery
> > service. But I really think that's way beyond what you are trying to
> > accomplish right now.
>
> My turn to learn something here. Tom, would you elaborate a bit on the above
> please? I know SRD's are comb generators out to visible light, but they're
> also 50 percent hard to find and 50 percent magic. I've been using
> Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
> promising myself that I'm gonna substitute an MMIC for that one day, I DID
> find the "Filter Gain" in the line length from generator to filter), THAT
> was both impressive AND helpful. If I go with the MMIC, any preference of
> Silicon over GaAs?
>
> Regards
>
> W4ZCB

[Tom Bruhns]

Hi Harold,

Nice of John to make that offer!

As for background and theory, I'll make copies of an artcile or two to
send you, about the discovery of the effect and the optimization of
diode structure to enhance it. I suppose that the effect you're
seeing with the Schottkys is almost entirely capacitive stored charge,
and that won't "sweep out" of the diode with the sharp step you get
with a step-recovery diode. The articles I'll send have info about
efficiency, which can be surprisingly high considering the high order
of multiplication.

Cheers,
Tom

"Harold E. Johnson" > wrote in message news:<3QBec.21137$_K3.55643@attbi_s53>...
> > If you do use diodes for higher-order harmonic generation, and not
> > just a simple full-wave-rectifier type frequency doubler, I suppose
> > you want something of the nature of a step recovery diode. That
> > implies minority carrier stored charge in the diode, and that would
> > preclude using a Schottky diode (which would work great in the
> > full-wave-rectifier type doubler). If you get into actually wanting
> > to generate harmonic combs out to microwave frequencies, it's probably
> > worthwhile looking for diodes actually characterized for step recovery
> > service. But I really think that's way beyond what you are trying to
> > accomplish right now.
>
> My turn to learn something here. Tom, would you elaborate a bit on the above
> please? I know SRD's are comb generators out to visible light, but they're
> also 50 percent hard to find and 50 percent magic. I've been using
> Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
> promising myself that I'm gonna substitute an MMIC for that one day, I DID
> find the "Filter Gain" in the line length from generator to filter), THAT
> was both impressive AND helpful. If I go with the MMIC, any preference of
> Silicon over GaAs?
>
> Regards
>
> W4ZCB

[John Larkin]

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.
>
>Cheers,
>Tom
>

Tom,

I'd appreciate a copy of that stuff. The history of the Boff Diode is
kinda neat.

I have some papers (hardcopy... faxable) on the Grehkov-effect drift
step-recovery diode; we use it to make 2400-volt, 3 ns wide pulses at
500 KHz, as long as the cold water keeps flowing.

John

[John Larkin]

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.
>
>Cheers,
>Tom
>

Tom,

I'd appreciate a copy of that stuff. The history of the Boff Diode is
kinda neat.

I have some papers (hardcopy... faxable) on the Grehkov-effect drift
step-recovery diode; we use it to make 2400-volt, 3 ns wide pulses at
500 KHz, as long as the cold water keeps flowing.

John

[Harold E. Johnson]

> >Nice of John to make that offer!
> >
You bet! MaCom is no HP however, and their "data sheets" are awfully skimpy.
I can almost put money on losing at least one finding out how sturdy they
are.

> >As for background and theory, I'll make copies of an artcile or two to
> >send you, about the discovery of the effect and the optimization of
> >diode structure to enhance it.

Will appreciate that as well Tom. I don't have to know the physics to make
use of the device, but it's helpful to have that insight when you're trying
to optimize the circuitry.

W4ZCB

[Harold E. Johnson]

> >Nice of John to make that offer!
> >
You bet! MaCom is no HP however, and their "data sheets" are awfully skimpy.
I can almost put money on losing at least one finding out how sturdy they
are.

> >As for background and theory, I'll make copies of an artcile or two to
> >send you, about the discovery of the effect and the optimization of
> >diode structure to enhance it.

Will appreciate that as well Tom. I don't have to know the physics to make
use of the device, but it's helpful to have that insight when you're trying
to optimize the circuitry.

W4ZCB

[Paul Burridge]

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.

What's a sensible target for the multiplication factor using diodes
from say a 4Mhz source? I'd be nice to go straight to say 20X on
account of the large physical size of the filters at lower HF., not to
mention the savings on intermediate stages.

[Paul Burridge]

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.

What's a sensible target for the multiplication factor using diodes
from say a 4Mhz source? I'd be nice to go straight to say 20X on
account of the large physical size of the filters at lower HF., not to
mention the savings on intermediate stages.

[Harold E. Johnson]

> What's a sensible target for the multiplication factor using diodes
> from say a 4Mhz source? I'd be nice to go straight to say 20X on
> account of the large physical size of the filters at lower HF., not to
> mention the savings on intermediate stages.

An 8 MHz filter doesn't have to be physically large Paul, and efficiency
drops pretty fast (Think like a rock) as the multiplication factor goes up.
Have you ever actually defined what it is you're trying to do? Some control
thing in your 70 MHz band? Or real power for some application? Hard to hit a
moving target. Or is that the idea?

W4ZCB

[Harold E. Johnson]

> What's a sensible target for the multiplication factor using diodes
> from say a 4Mhz source? I'd be nice to go straight to say 20X on
> account of the large physical size of the filters at lower HF., not to
> mention the savings on intermediate stages.

An 8 MHz filter doesn't have to be physically large Paul, and efficiency
drops pretty fast (Think like a rock) as the multiplication factor goes up.
Have you ever actually defined what it is you're trying to do? Some control
thing in your 70 MHz band? Or real power for some application? Hard to hit a
moving target. Or is that the idea?

W4ZCB

[Tony]

This is a good learning experience for lots of us out here. Any chance of
scanning the printed material and posting , say on a.b.s.e?

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.
>
>Cheers,
>Tom
>
>"Harold E. Johnson" > wrote in message news:<3QBec.21137$_K3.55643@attbi_s53>...
>> > If you do use diodes for higher-order harmonic generation, and not
>> > just a simple full-wave-rectifier type frequency doubler, I suppose
>> > you want something of the nature of a step recovery diode. That
>> > implies minority carrier stored charge in the diode, and that would
>> > preclude using a Schottky diode (which would work great in the
>> > full-wave-rectifier type doubler). If you get into actually wanting
>> > to generate harmonic combs out to microwave frequencies, it's probably
>> > worthwhile looking for diodes actually characterized for step recovery
>> > service. But I really think that's way beyond what you are trying to
>> > accomplish right now.
>>
>> My turn to learn something here. Tom, would you elaborate a bit on the above
>> please? I know SRD's are comb generators out to visible light, but they're
>> also 50 percent hard to find and 50 percent magic. I've been using
>> Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
>> promising myself that I'm gonna substitute an MMIC for that one day, I DID
>> find the "Filter Gain" in the line length from generator to filter), THAT
>> was both impressive AND helpful. If I go with the MMIC, any preference of
>> Silicon over GaAs?
>>
>> Regards
>>
>> W4ZCB

Tony (remove the "_" to reply by email)

[Tony]

This is a good learning experience for lots of us out here. Any chance of
scanning the printed material and posting , say on a.b.s.e?

On 13 Apr 2004 10:44:19 -0700, (Tom Bruhns) wrote:

>Hi Harold,
>
>Nice of John to make that offer!
>
>As for background and theory, I'll make copies of an artcile or two to
>send you, about the discovery of the effect and the optimization of
>diode structure to enhance it. I suppose that the effect you're
>seeing with the Schottkys is almost entirely capacitive stored charge,
>and that won't "sweep out" of the diode with the sharp step you get
>with a step-recovery diode. The articles I'll send have info about
>efficiency, which can be surprisingly high considering the high order
>of multiplication.
>
>Cheers,
>Tom
>
>"Harold E. Johnson" > wrote in message news:<3QBec.21137$_K3.55643@attbi_s53>...
>> > If you do use diodes for higher-order harmonic generation, and not
>> > just a simple full-wave-rectifier type frequency doubler, I suppose
>> > you want something of the nature of a step recovery diode. That
>> > implies minority carrier stored charge in the diode, and that would
>> > preclude using a Schottky diode (which would work great in the
>> > full-wave-rectifier type doubler). If you get into actually wanting
>> > to generate harmonic combs out to microwave frequencies, it's probably
>> > worthwhile looking for diodes actually characterized for step recovery
>> > service. But I really think that's way beyond what you are trying to
>> > accomplish right now.
>>
>> My turn to learn something here. Tom, would you elaborate a bit on the above
>> please? I know SRD's are comb generators out to visible light, but they're
>> also 50 percent hard to find and 50 percent magic. I've been using
>> Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
>> promising myself that I'm gonna substitute an MMIC for that one day, I DID
>> find the "Filter Gain" in the line length from generator to filter), THAT
>> was both impressive AND helpful. If I go with the MMIC, any preference of
>> Silicon over GaAs?
>>
>> Regards
>>
>> W4ZCB

Tony (remove the "_" to reply by email)

[Tom Bruhns]

Paul Burridge > wrote in message >...

> What's a sensible target for the multiplication factor using diodes
> from say a 4Mhz source? I'd be nice to go straight to say 20X on
> account of the large physical size of the filters at lower HF., not to
> mention the savings on intermediate stages.

Well, somewhat counter to what Harold wrote, the old HP Journal
article I've dredged out to copy says a step recovery diode can do 20X
at 30% efficiency. But that's guys who really understood what they
were doing! (Just coincidentally, the one table they have is for
20X!)

He's right...the filters don't have to be huge. But I'd think of them
as large compared with a SOT-23. The tradeoff is that if you do it
all in one step, you have to have a filter sharp enough to take the
19x and 21x down to your desired level, whatever that is. But with a
5x and a 4x, you can use a couple filters with wider percentage
bandwidths, since for the 5x you'll be using a square-wave input which
has practically no 4th and 6th anyway, and the 3rd and 7th are a big
percentage removed from the 5th...and the 4x can similarly avoid the
3rd and 5th if you do it right.

But again, a PLL can be very small indeed. And I never did see an
answer to the question about does it really need to be locked to your
low freq, or can it be a separate xtal at 70MHz or whatever?

Cheers,
Tom

[Tom Bruhns]

Paul Burridge > wrote in message >...

> What's a sensible target for the multiplication factor using diodes
> from say a 4Mhz source? I'd be nice to go straight to say 20X on
> account of the large physical size of the filters at lower HF., not to
> mention the savings on intermediate stages.

Well, somewhat counter to what Harold wrote, the old HP Journal
article I've dredged out to copy says a step recovery diode can do 20X
at 30% efficiency. But that's guys who really understood what they
were doing! (Just coincidentally, the one table they have is for
20X!)

He's right...the filters don't have to be huge. But I'd think of them
as large compared with a SOT-23. The tradeoff is that if you do it
all in one step, you have to have a filter sharp enough to take the
19x and 21x down to your desired level, whatever that is. But with a
5x and a 4x, you can use a couple filters with wider percentage
bandwidths, since for the 5x you'll be using a square-wave input which
has practically no 4th and 6th anyway, and the 3rd and 7th are a big
percentage removed from the 5th...and the 4x can similarly avoid the
3rd and 5th if you do it right.

But again, a PLL can be very small indeed. And I never did see an
answer to the question about does it really need to be locked to your
low freq, or can it be a separate xtal at 70MHz or whatever?

Cheers,
Tom

[Paul Burridge]

On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> wrote:


>An 8 MHz filter doesn't have to be physically large Paul,

Hi Q coils in that frequency range in compact sizes... they don't seem
to go together. :-(

>and efficiency
>drops pretty fast (Think like a rock) as the multiplication factor goes up.
>Have you ever actually defined what it is you're trying to do? Some control
>thing in your 70 MHz band? Or real power for some application? Hard to hit a
>moving target. Or is that the idea?

Yeah, moving target's good. Keep the discussion generalised and it
might help others as well. I'm not sure where the 70Mhz figure comes
from, but it's a good enough guess by whoever made it. However, the
final desired frequency in my particular case is in the region of
40Mhz which will be achieved by mixing down with the output from
another oscillator and filtering.

[Paul Burridge]

On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> wrote:


>An 8 MHz filter doesn't have to be physically large Paul,

Hi Q coils in that frequency range in compact sizes... they don't seem
to go together. :-(

>and efficiency
>drops pretty fast (Think like a rock) as the multiplication factor goes up.
>Have you ever actually defined what it is you're trying to do? Some control
>thing in your 70 MHz band? Or real power for some application? Hard to hit a
>moving target. Or is that the idea?

Yeah, moving target's good. Keep the discussion generalised and it
might help others as well. I'm not sure where the 70Mhz figure comes
from, but it's a good enough guess by whoever made it. However, the
final desired frequency in my particular case is in the region of
40Mhz which will be achieved by mixing down with the output from
another oscillator and filtering.

[Tom Bruhns]

Tony > wrote in message >...
> This is a good learning experience for lots of us out here. Any chance of
> scanning the printed material and posting , say on a.b.s.e?

Nope, sorry. I don't have access to the binaries groups, and in
addition, it's copyrighted material. I'm willing to make a very
limited number of copies, but not to post it.

The articles I have are old HP Journal articles, available in
"Inventions of Opportunity," copyright Hewlett-Packard Company, 1983,
ISBN 0-9612030-0-5. You may be able to find that in your library.
The articles in that book were chosen to represent seminal ideas and
products that opened new horizons, so the SRD items are as much for
historical interest as for technical info.

You'll find a little more modern technical info in HP AN-1054,
available at http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.

Cheers,
Tom

[Tom Bruhns]

Tony > wrote in message >...
> This is a good learning experience for lots of us out here. Any chance of
> scanning the printed material and posting , say on a.b.s.e?

Nope, sorry. I don't have access to the binaries groups, and in
addition, it's copyrighted material. I'm willing to make a very
limited number of copies, but not to post it.

The articles I have are old HP Journal articles, available in
"Inventions of Opportunity," copyright Hewlett-Packard Company, 1983,
ISBN 0-9612030-0-5. You may be able to find that in your library.
The articles in that book were chosen to represent seminal ideas and
products that opened new horizons, so the SRD items are as much for
historical interest as for technical info.

You'll find a little more modern technical info in HP AN-1054,
available at http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.

Cheers,
Tom

[Harold E. Johnson]

> You'll find a little more modern technical info in HP AN-1054,
> available at
http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.
>
T'aint fair Tom! That URL is FB and I have it added to my library, but when
I tried to trick it and deleted the AN-1054.PDF, and retyped AN-983.PDF, it
can't find that one. Suppose I could write a little program to check AN-1
and step 1 then find out what if anything I had. Is there some secret code
as to how this all works?

Regards

W4ZCB

(I suppoe it wouldn't be a secret anymore if you told me.)

[Harold E. Johnson]

> You'll find a little more modern technical info in HP AN-1054,
> available at
http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.
>
T'aint fair Tom! That URL is FB and I have it added to my library, but when
I tried to trick it and deleted the AN-1054.PDF, and retyped AN-983.PDF, it
can't find that one. Suppose I could write a little program to check AN-1
and step 1 then find out what if anything I had. Is there some secret code
as to how this all works?

Regards

W4ZCB

(I suppoe it wouldn't be a secret anymore if you told me.)

[Tom Bruhns]

"Harold E. Johnson" > wrote in message news:<YKjfc.38031$_K3.164147@attbi_s53>...
> > You'll find a little more modern technical info in HP AN-1054,
> > available at
> http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.
> >
> T'aint fair Tom!

Ja, life's like dat.

> That URL is FB and I have it added to my library, but when
> I tried to trick it and deleted the AN-1054.PDF, and retyped AN-983.PDF, it
> can't find that one. Suppose I could write a little program to check AN-1
> and step 1 then find out what if anything I had. Is there some secret code
> as to how this all works?

Well, I just typed a search string about SRDs into Google to find the
AN1054 reference. I don't have any magical ideas about finding ALL of
them on the web, but when I moved out library a few months ago, I made
a point of NOT tossing out the ap notes. There's a chance we have it
at work. Now, can I remember to look? Luckily, I didn't find enough
stamps to mail the other stuff off to you and John yet, so if I can
find it, I can stick that one in too. Best magic I can think of for
it at the moment. There are some other SRD-related ones listed in my
Communications Components catalog from 1993: AN918, AN928, (AN983),
AN984, AN989. It does list HP part numbers for each one. "To order
literature, ... 1-800-537-7715" but that's from a long time ago...

Cheers,
Tom

[Tom Bruhns]

"Harold E. Johnson" > wrote in message news:<YKjfc.38031$_K3.164147@attbi_s53>...
> > You'll find a little more modern technical info in HP AN-1054,
> > available at
> http://rf.rfglobalnet.com/library/ApplicationNotes/files/1/An1054.pdf.
> >
> T'aint fair Tom!

Ja, life's like dat.

> That URL is FB and I have it added to my library, but when
> I tried to trick it and deleted the AN-1054.PDF, and retyped AN-983.PDF, it
> can't find that one. Suppose I could write a little program to check AN-1
> and step 1 then find out what if anything I had. Is there some secret code
> as to how this all works?

Well, I just typed a search string about SRDs into Google to find the
AN1054 reference. I don't have any magical ideas about finding ALL of
them on the web, but when I moved out library a few months ago, I made
a point of NOT tossing out the ap notes. There's a chance we have it
at work. Now, can I remember to look? Luckily, I didn't find enough
stamps to mail the other stuff off to you and John yet, so if I can
find it, I can stick that one in too. Best magic I can think of for
it at the moment. There are some other SRD-related ones listed in my
Communications Components catalog from 1993: AN918, AN928, (AN983),
AN984, AN989. It does list HP part numbers for each one. "To order
literature, ... 1-800-537-7715" but that's from a long time ago...

Cheers,
Tom

[Barry Lennox]

On Mon, 12 Apr 2004 12:23:09 -0700, John Larkin
> wrote:


>
>The only distributor-stock SRDs I know of are the M/Acom MA44767,
>MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>carries them. The '68 or '69 should be good for multiplication to 2
>GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>There are lots of appnotes around about using them as multipliers.
>
>I have a bunch in stock and can send a few to anybody who wants to
>play.

MPulse microwave used to be pretty good with samples, I have some
MP4065 SRDs that work well.

Tel # used to be 408 432 1480

Barry lennox

[Barry Lennox]

On Mon, 12 Apr 2004 12:23:09 -0700, John Larkin
> wrote:


>
>The only distributor-stock SRDs I know of are the M/Acom MA44767,
>MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>carries them. The '68 or '69 should be good for multiplication to 2
>GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>There are lots of appnotes around about using them as multipliers.
>
>I have a bunch in stock and can send a few to anybody who wants to
>play.

MPulse microwave used to be pretty good with samples, I have some
MP4065 SRDs that work well.

Tel # used to be 408 432 1480

Barry lennox

[Harold E. Johnson]

> Well, I just typed a search string about SRDs into Google to find the
> AN1054 reference. I don't have any magical ideas about finding ALL of
> them on the web, but when I moved out library a few months ago, I made
> a point of NOT tossing out the ap notes. There's a chance we have it
> at work. Now, can I remember to look?

DOn't worry about finding AN983, I have a dog-eared copy here. If YOU want a
copy, I can do the reverse lend-lease thing.

W4ZCB

[Harold E. Johnson]

> Well, I just typed a search string about SRDs into Google to find the
> AN1054 reference. I don't have any magical ideas about finding ALL of
> them on the web, but when I moved out library a few months ago, I made
> a point of NOT tossing out the ap notes. There's a chance we have it
> at work. Now, can I remember to look?

DOn't worry about finding AN983, I have a dog-eared copy here. If YOU want a
copy, I can do the reverse lend-lease thing.

W4ZCB

[John Larkin]

On Thu, 15 Apr 2004 20:12:40 +1200, Barry Lennox
> wrote:

>On Mon, 12 Apr 2004 12:23:09 -0700, John Larkin
> wrote:
>
>
>>
>>The only distributor-stock SRDs I know of are the M/Acom MA44767,
>>MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>>carries them. The '68 or '69 should be good for multiplication to 2
>>GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>>There are lots of appnotes around about using them as multipliers.
>>
>>I have a bunch in stock and can send a few to anybody who wants to
>>play.
>
>MPulse microwave used to be pretty good with samples, I have some
>MP4065 SRDs that work well.
>
>Tel # used to be 408 432 1480
>
>Barry lennox

M-Pulse is good guys; we use some of their faster parts, and they are
very helpful. But they apparently don't stock anything, and wire-bond
- even samples - to order. So if you only want a few pieces for
yourself, and don't intend to place a production order, you'll have to
lie to them to get samples.

Metelics is similar; they seem to make the fastest SRD (35 ps) you can
buy on the open market. Not as friendly as M-Pulse, though.

John

[John Larkin]

On Thu, 15 Apr 2004 20:12:40 +1200, Barry Lennox
> wrote:

>On Mon, 12 Apr 2004 12:23:09 -0700, John Larkin
> wrote:
>
>
>>
>>The only distributor-stock SRDs I know of are the M/Acom MA44767,
>>MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
>>carries them. The '68 or '69 should be good for multiplication to 2
>>GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
>>There are lots of appnotes around about using them as multipliers.
>>
>>I have a bunch in stock and can send a few to anybody who wants to
>>play.
>
>MPulse microwave used to be pretty good with samples, I have some
>MP4065 SRDs that work well.
>
>Tel # used to be 408 432 1480
>
>Barry lennox

M-Pulse is good guys; we use some of their faster parts, and they are
very helpful. But they apparently don't stock anything, and wire-bond
- even samples - to order. So if you only want a few pieces for
yourself, and don't intend to place a production order, you'll have to
lie to them to get samples.

Metelics is similar; they seem to make the fastest SRD (35 ps) you can
buy on the open market. Not as friendly as M-Pulse, though.

John

[Robert Baer]

Paul Burridge wrote:
>
> On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> > wrote:
>
> >An 8 MHz filter doesn't have to be physically large Paul,
>
> Hi Q coils in that frequency range in compact sizes... they don't seem
> to go together. :-(
>
> >and efficiency
> >drops pretty fast (Think like a rock) as the multiplication factor goes up.
> >Have you ever actually defined what it is you're trying to do? Some control
> >thing in your 70 MHz band? Or real power for some application? Hard to hit a
> >moving target. Or is that the idea?
>
> Yeah, moving target's good. Keep the discussion generalised and it
> might help others as well. I'm not sure where the 70Mhz figure comes
> from, but it's a good enough guess by whoever made it. However, the
> final desired frequency in my particular case is in the region of
> 40Mhz which will be achieved by mixing down with the output from
> another oscillator and filtering.

A high Q resonant circuit can be rather small.
For example, i made a tunable LC with a Q approaching 1000, and it was
not the size of a garbage can (resonant cavity); it was about 5 inches
tall and about 3 inches in diameter.
On one extreme, one uses standard LC parts and get fair Qs in small
size.
On the other extreme, one makes a ersonant cavity to get very high Qs
at the expense of size.
In between there is something that can be called either a "shielded
inductor" or a "resonant cavity with slow wave structure".
One takes an inductor and places it in the center of a metal cylinder;
one end of the inductor attaches to the inner wall (makes electrical
connection and acts as support).
The capacitance to the walls (and added ends) is the other half. Move
an end for fine tuning.
Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
desigh equations.
The terminology used was "Helical resonator".

[Robert Baer]

Paul Burridge wrote:
>
> On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> > wrote:
>
> >An 8 MHz filter doesn't have to be physically large Paul,
>
> Hi Q coils in that frequency range in compact sizes... they don't seem
> to go together. :-(
>
> >and efficiency
> >drops pretty fast (Think like a rock) as the multiplication factor goes up.
> >Have you ever actually defined what it is you're trying to do? Some control
> >thing in your 70 MHz band? Or real power for some application? Hard to hit a
> >moving target. Or is that the idea?
>
> Yeah, moving target's good. Keep the discussion generalised and it
> might help others as well. I'm not sure where the 70Mhz figure comes
> from, but it's a good enough guess by whoever made it. However, the
> final desired frequency in my particular case is in the region of
> 40Mhz which will be achieved by mixing down with the output from
> another oscillator and filtering.

A high Q resonant circuit can be rather small.
For example, i made a tunable LC with a Q approaching 1000, and it was
not the size of a garbage can (resonant cavity); it was about 5 inches
tall and about 3 inches in diameter.
On one extreme, one uses standard LC parts and get fair Qs in small
size.
On the other extreme, one makes a ersonant cavity to get very high Qs
at the expense of size.
In between there is something that can be called either a "shielded
inductor" or a "resonant cavity with slow wave structure".
One takes an inductor and places it in the center of a metal cylinder;
one end of the inductor attaches to the inner wall (makes electrical
connection and acts as support).
The capacitance to the walls (and added ends) is the other half. Move
an end for fine tuning.
Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
desigh equations.
The terminology used was "Helical resonator".

[Reg Edwards]

It may be of interest -

Doubling the length and diameter of a solenoid and reducing the number of
turns of thicker wire to maintain the same inductance, doubles the Q until
radiation loss resistance begins to predominate.

And it's a big coil for radiation resistance to predominate.
----
Reg, G4FGQ

[Reg Edwards]

It may be of interest -

Doubling the length and diameter of a solenoid and reducing the number of
turns of thicker wire to maintain the same inductance, doubles the Q until
radiation loss resistance begins to predominate.

And it's a big coil for radiation resistance to predominate.
----
Reg, G4FGQ

[John Larkin]

On Fri, 16 Apr 2004 08:19:10 GMT, Robert Baer
> wrote:

>Paul Burridge wrote:
>>
>> On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
>> > wrote:
>>
>> >An 8 MHz filter doesn't have to be physically large Paul,
>>
>> Hi Q coils in that frequency range in compact sizes... they don't seem
>> to go together. :-(
>>
>> >and efficiency
>> >drops pretty fast (Think like a rock) as the multiplication factor goes up.
>> >Have you ever actually defined what it is you're trying to do? Some control
>> >thing in your 70 MHz band? Or real power for some application? Hard to hit a
>> >moving target. Or is that the idea?
>>
>> Yeah, moving target's good. Keep the discussion generalised and it
>> might help others as well. I'm not sure where the 70Mhz figure comes
>> from, but it's a good enough guess by whoever made it. However, the
>> final desired frequency in my particular case is in the region of
>> 40Mhz which will be achieved by mixing down with the output from
>> another oscillator and filtering.
>
> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
>not the size of a garbage can (resonant cavity); it was about 5 inches
>tall and about 3 inches in diameter.
> On one extreme, one uses standard LC parts and get fair Qs in small
>size.
> On the other extreme, one makes a ersonant cavity to get very high Qs
>at the expense of size.
> In between there is something that can be called either a "shielded
>inductor" or a "resonant cavity with slow wave structure".
> One takes an inductor and places it in the center of a metal cylinder;
>one end of the inductor attaches to the inner wall (makes electrical
>connection and acts as support).
> The capacitance to the walls (and added ends) is the other half. Move
>an end for fine tuning.
> Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
>desigh equations.
> The terminology used was "Helical resonator".

Coaxial ceramic resonators are cool... they are small, extremely
stable, and have Qs in the thousands.

John

[John Larkin]

On Fri, 16 Apr 2004 08:19:10 GMT, Robert Baer
> wrote:

>Paul Burridge wrote:
>>
>> On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
>> > wrote:
>>
>> >An 8 MHz filter doesn't have to be physically large Paul,
>>
>> Hi Q coils in that frequency range in compact sizes... they don't seem
>> to go together. :-(
>>
>> >and efficiency
>> >drops pretty fast (Think like a rock) as the multiplication factor goes up.
>> >Have you ever actually defined what it is you're trying to do? Some control
>> >thing in your 70 MHz band? Or real power for some application? Hard to hit a
>> >moving target. Or is that the idea?
>>
>> Yeah, moving target's good. Keep the discussion generalised and it
>> might help others as well. I'm not sure where the 70Mhz figure comes
>> from, but it's a good enough guess by whoever made it. However, the
>> final desired frequency in my particular case is in the region of
>> 40Mhz which will be achieved by mixing down with the output from
>> another oscillator and filtering.
>
> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
>not the size of a garbage can (resonant cavity); it was about 5 inches
>tall and about 3 inches in diameter.
> On one extreme, one uses standard LC parts and get fair Qs in small
>size.
> On the other extreme, one makes a ersonant cavity to get very high Qs
>at the expense of size.
> In between there is something that can be called either a "shielded
>inductor" or a "resonant cavity with slow wave structure".
> One takes an inductor and places it in the center of a metal cylinder;
>one end of the inductor attaches to the inner wall (makes electrical
>connection and acts as support).
> The capacitance to the walls (and added ends) is the other half. Move
>an end for fine tuning.
> Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
>desigh equations.
> The terminology used was "Helical resonator".

Coaxial ceramic resonators are cool... they are small, extremely
stable, and have Qs in the thousands.

John

[Reg Edwards]

> Coaxial ceramic resonators are cool... they are small, extremely
> stable, and have Qs in the thousands.
>
How do you measure the Qs of resonators in the thousands?

[Reg Edwards]

> Coaxial ceramic resonators are cool... they are small, extremely
> stable, and have Qs in the thousands.
>
How do you measure the Qs of resonators in the thousands?

[Tom Bruhns]

Robert Baer > wrote in message >...
....
> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
> not the size of a garbage can (resonant cavity); it was about 5 inches
> tall and about 3 inches in diameter.

Based on an earlier P.Burridge thread, I'd say that's NOT small for
him. Of course, you didn't mention the frequency (I'd guess around
10MHz), but in the earlier thread, I was suggesting that he use a coil
at 18MHz or so with a Qu around 100, and he didn't seem to like even
the rather small size that one could make such a coil. I did it on,
um either a .68" OD or .80" OD powdered iron toroid, and that was
apparently too big. I also suggested a multi-pole filter which could
give the same effective filtering, and could use three small SMT
inductors. I gathered even that was too big. And I suppose coaxial
ceramic resonators for one-off projects at 18MHz aren't very
practical...

> On one extreme, one uses standard LC parts and get fair Qs in small
> size.
> On the other extreme, one makes a ersonant cavity to get very high Qs
> at the expense of size.
> In between there is something that can be called either a "shielded
> inductor" or a "resonant cavity with slow wave structure".

There seems to be a popular misconception that a helical resonator
gives better Q than an unshielded coil and capacitor. One of the key
nice things about helical resonators is that they are well
shielded...there's extremely little external field. That lets you
stack several of them side-by-side, with appropriately chosen coupling
apertures between the cavities, to make a nice, compact multi-pole
filter. But let's not assign a quality that isn't there: the same
coil WITHOUT the shield will have a higher Qu, so long as it's not so
huge that radiation is a significant loss mechanism, and as Reg
suggests, that's BIG for most of the tanks we think about. In the
older editions of "Reference Data for Radio Engineers," e.g. the fifth
edition, there are some design nomographs for helical resonators in
the Transmission Lines chapter. They will give you the Qu. If you
find the Qu of the coil in air (see the same book, Fundamentals of
Networks chapter, or use Reg's coil program or WAIRCOIL), you'll see
that the coil's Qu is higher. And if you look also in the Fund. of
Networks chapter, you'll find a graph for the decrease of inductance
of a coil when shielded, and you'll find that that almost exactly
accounts for the Q lowering: same effective series resistance, but
lower inductance, gives lower Q. Is it significant? Well, I think
for a typical helical resonator, it's a 15% to 25% lowering.

Mainly I want to dispell the notion that a helical resonator is
something magic that _raises_ the Q of a given coil, because it's not.
It does have some very nice properties, but that just isn't one of
them.

Early helical resonator reference: W. W. Macalpine and R. O.
Schildknecht, "Coaxial Resonators with Helical Inner Conductor," Proc.
of the IRE, Dec. 1959 -- almost 45 years ago now.

Cheers,
Tom

[Tom Bruhns]

Robert Baer > wrote in message >...
....
> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
> not the size of a garbage can (resonant cavity); it was about 5 inches
> tall and about 3 inches in diameter.

Based on an earlier P.Burridge thread, I'd say that's NOT small for
him. Of course, you didn't mention the frequency (I'd guess around
10MHz), but in the earlier thread, I was suggesting that he use a coil
at 18MHz or so with a Qu around 100, and he didn't seem to like even
the rather small size that one could make such a coil. I did it on,
um either a .68" OD or .80" OD powdered iron toroid, and that was
apparently too big. I also suggested a multi-pole filter which could
give the same effective filtering, and could use three small SMT
inductors. I gathered even that was too big. And I suppose coaxial
ceramic resonators for one-off projects at 18MHz aren't very
practical...

> On one extreme, one uses standard LC parts and get fair Qs in small
> size.
> On the other extreme, one makes a ersonant cavity to get very high Qs
> at the expense of size.
> In between there is something that can be called either a "shielded
> inductor" or a "resonant cavity with slow wave structure".

There seems to be a popular misconception that a helical resonator
gives better Q than an unshielded coil and capacitor. One of the key
nice things about helical resonators is that they are well
shielded...there's extremely little external field. That lets you
stack several of them side-by-side, with appropriately chosen coupling
apertures between the cavities, to make a nice, compact multi-pole
filter. But let's not assign a quality that isn't there: the same
coil WITHOUT the shield will have a higher Qu, so long as it's not so
huge that radiation is a significant loss mechanism, and as Reg
suggests, that's BIG for most of the tanks we think about. In the
older editions of "Reference Data for Radio Engineers," e.g. the fifth
edition, there are some design nomographs for helical resonators in
the Transmission Lines chapter. They will give you the Qu. If you
find the Qu of the coil in air (see the same book, Fundamentals of
Networks chapter, or use Reg's coil program or WAIRCOIL), you'll see
that the coil's Qu is higher. And if you look also in the Fund. of
Networks chapter, you'll find a graph for the decrease of inductance
of a coil when shielded, and you'll find that that almost exactly
accounts for the Q lowering: same effective series resistance, but
lower inductance, gives lower Q. Is it significant? Well, I think
for a typical helical resonator, it's a 15% to 25% lowering.

Mainly I want to dispell the notion that a helical resonator is
something magic that _raises_ the Q of a given coil, because it's not.
It does have some very nice properties, but that just isn't one of
them.

Early helical resonator reference: W. W. Macalpine and R. O.
Schildknecht, "Coaxial Resonators with Helical Inner Conductor," Proc.
of the IRE, Dec. 1959 -- almost 45 years ago now.

Cheers,
Tom

[John Larkin]

On Fri, 16 Apr 2004 19:10:18 +0000 (UTC), "Reg Edwards"
> wrote:

>> Coaxial ceramic resonators are cool... they are small, extremely
>> stable, and have Qs in the thousands.
>>
>How do you measure the Qs of resonators in the thousands?
>

Well, all the usual methods: resonance width, phase shift, ringdown,
stuff like that. I work with gadgets with Qs over 1e9, and people
measure them without difficulty.

John

[John Larkin]

On Fri, 16 Apr 2004 19:10:18 +0000 (UTC), "Reg Edwards"
> wrote:

>> Coaxial ceramic resonators are cool... they are small, extremely
>> stable, and have Qs in the thousands.
>>
>How do you measure the Qs of resonators in the thousands?
>

Well, all the usual methods: resonance width, phase shift, ringdown,
stuff like that. I work with gadgets with Qs over 1e9, and people
measure them without difficulty.

John

[Scott Stephens]

Robert Baer wrote:

> Paul Burridge wrote:
>
>>On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> wrote:
>>
>>
>>>An 8 MHz filter doesn't have to be physically large Paul,
>>
>>Hi Q coils in that frequency range in compact sizes... they don't seem
>>to go together. :-(

> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
> not the size of a garbage can (resonant cavity); it was about 5 inches
> tall and about 3 inches in diameter.

That doesn't sound very small.

> On one extreme, one uses standard LC parts and get fair Qs in small
> size.

You can also use positive feedback (negative resistance) to sharpen Q,
if you are somewhat careful or don't mind tweaking.

> Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
> desigh equations.
> The terminology used was "Helical resonator".

The ARRL Handbook has/had a design table for them too.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

[Scott Stephens]

Robert Baer wrote:

> Paul Burridge wrote:
>
>>On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> wrote:
>>
>>
>>>An 8 MHz filter doesn't have to be physically large Paul,
>>
>>Hi Q coils in that frequency range in compact sizes... they don't seem
>>to go together. :-(

> A high Q resonant circuit can be rather small.
> For example, i made a tunable LC with a Q approaching 1000, and it was
> not the size of a garbage can (resonant cavity); it was about 5 inches
> tall and about 3 inches in diameter.

That doesn't sound very small.

> On one extreme, one uses standard LC parts and get fair Qs in small
> size.

You can also use positive feedback (negative resistance) to sharpen Q,
if you are somewhat careful or don't mind tweaking.

> Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
> desigh equations.
> The terminology used was "Helical resonator".

The ARRL Handbook has/had a design table for them too.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

[Robert Baer]

Reg Edwards wrote:
>
> It may be of interest -
>
> Doubling the length and diameter of a solenoid and reducing the number of
> turns of thicker wire to maintain the same inductance, doubles the Q until
> radiation loss resistance begins to predominate.
>
> And it's a big coil for radiation resistance to predominate.
> ----
> Reg, G4FGQ

....and like i mentioned, put a (cylindrical) shield around it and you
still have a high Q and a lower frequency *due to the higher distributed
capacitance.
Alternately, use it as a slow wave structure in a (resonant)
cavity)...

(same difference)

[Robert Baer]

Reg Edwards wrote:
>
> It may be of interest -
>
> Doubling the length and diameter of a solenoid and reducing the number of
> turns of thicker wire to maintain the same inductance, doubles the Q until
> radiation loss resistance begins to predominate.
>
> And it's a big coil for radiation resistance to predominate.
> ----
> Reg, G4FGQ

....and like i mentioned, put a (cylindrical) shield around it and you
still have a high Q and a lower frequency *due to the higher distributed
capacitance.
Alternately, use it as a slow wave structure in a (resonant)
cavity)...

(same difference)

[Robert Baer]

Reg Edwards wrote:
>
> > Coaxial ceramic resonators are cool... they are small, extremely
> > stable, and have Qs in the thousands.
> >
> How do you measure the Qs of resonators in the thousands?

The three dog-bone method, perhaps?

[Robert Baer]

Reg Edwards wrote:
>
> > Coaxial ceramic resonators are cool... they are small, extremely
> > stable, and have Qs in the thousands.
> >
> How do you measure the Qs of resonators in the thousands?

The three dog-bone method, perhaps?

[Robert Baer]

John Larkin wrote:
>
> On Fri, 16 Apr 2004 19:10:18 +0000 (UTC), "Reg Edwards"
> > wrote:
>
> >> Coaxial ceramic resonators are cool... they are small, extremely
> >> stable, and have Qs in the thousands.
> >>
> >How do you measure the Qs of resonators in the thousands?
> >
>
> Well, all the usual methods: resonance width, phase shift, ringdown,
> stuff like that. I work with gadgets with Qs over 1e9, and people
> measure them without difficulty.
>
> John

Ringdown is the easist way when Qs are extremely high.

[Robert Baer]

John Larkin wrote:
>
> On Fri, 16 Apr 2004 19:10:18 +0000 (UTC), "Reg Edwards"
> > wrote:
>
> >> Coaxial ceramic resonators are cool... they are small, extremely
> >> stable, and have Qs in the thousands.
> >>
> >How do you measure the Qs of resonators in the thousands?
> >
>
> Well, all the usual methods: resonance width, phase shift, ringdown,
> stuff like that. I work with gadgets with Qs over 1e9, and people
> measure them without difficulty.
>
> John

Ringdown is the easist way when Qs are extremely high.

[Robert Baer]

Tom Bruhns wrote:
>
> Robert Baer > wrote in message >...
> ...
> > A high Q resonant circuit can be rather small.
> > For example, i made a tunable LC with a Q approaching 1000, and it was
> > not the size of a garbage can (resonant cavity); it was about 5 inches
> > tall and about 3 inches in diameter.
>
> Based on an earlier P.Burridge thread, I'd say that's NOT small for
> him. Of course, you didn't mention the frequency (I'd guess around
> 10MHz), but in the earlier thread, I was suggesting that he use a coil
> at 18MHz or so with a Qu around 100, and he didn't seem to like even
> the rather small size that one could make such a coil. I did it on,
> um either a .68" OD or .80" OD powdered iron toroid, and that was
> apparently too big. I also suggested a multi-pole filter which could
> give the same effective filtering, and could use three small SMT
> inductors. I gathered even that was too big. And I suppose coaxial
> ceramic resonators for one-off projects at 18MHz aren't very
> practical...
>
> > On one extreme, one uses standard LC parts and get fair Qs in small
> > size.
> > On the other extreme, one makes a ersonant cavity to get very high Qs
> > at the expense of size.
> > In between there is something that can be called either a "shielded
> > inductor" or a "resonant cavity with slow wave structure".
>
> There seems to be a popular misconception that a helical resonator
> gives better Q than an unshielded coil and capacitor. One of the key
> nice things about helical resonators is that they are well
> shielded...there's extremely little external field. That lets you
> stack several of them side-by-side, with appropriately chosen coupling
> apertures between the cavities, to make a nice, compact multi-pole
> filter. But let's not assign a quality that isn't there: the same
> coil WITHOUT the shield will have a higher Qu, so long as it's not so
> huge that radiation is a significant loss mechanism, and as Reg
> suggests, that's BIG for most of the tanks we think about. In the
> older editions of "Reference Data for Radio Engineers," e.g. the fifth
> edition, there are some design nomographs for helical resonators in
> the Transmission Lines chapter. They will give you the Qu. If you
> find the Qu of the coil in air (see the same book, Fundamentals of
> Networks chapter, or use Reg's coil program or WAIRCOIL), you'll see
> that the coil's Qu is higher. And if you look also in the Fund. of
> Networks chapter, you'll find a graph for the decrease of inductance
> of a coil when shielded, and you'll find that that almost exactly
> accounts for the Q lowering: same effective series resistance, but
> lower inductance, gives lower Q. Is it significant? Well, I think
> for a typical helical resonator, it's a 15% to 25% lowering.
>
> Mainly I want to dispell the notion that a helical resonator is
> something magic that _raises_ the Q of a given coil, because it's not.
> It does have some very nice properties, but that just isn't one of
> them.
>
> Early helical resonator reference: W. W. Macalpine and R. O.
> Schildknecht, "Coaxial Resonators with Helical Inner Conductor," Proc.
> of the IRE, Dec. 1959 -- almost 45 years ago now.
>
> Cheers,
> Tom

Yes, but the emphasis was on small size, and a helical resonator
allows a goodly shrinkage of volume wihout a corresponding loss large of
Q.
But if the frequency is low enough, the ferite core method, if
properly wound, then becomes a "preferred" solution for small size and
high Q.
Maybe his requirements are not too realistic?

[Robert Baer]

Tom Bruhns wrote:
>
> Robert Baer > wrote in message >...
> ...
> > A high Q resonant circuit can be rather small.
> > For example, i made a tunable LC with a Q approaching 1000, and it was
> > not the size of a garbage can (resonant cavity); it was about 5 inches
> > tall and about 3 inches in diameter.
>
> Based on an earlier P.Burridge thread, I'd say that's NOT small for
> him. Of course, you didn't mention the frequency (I'd guess around
> 10MHz), but in the earlier thread, I was suggesting that he use a coil
> at 18MHz or so with a Qu around 100, and he didn't seem to like even
> the rather small size that one could make such a coil. I did it on,
> um either a .68" OD or .80" OD powdered iron toroid, and that was
> apparently too big. I also suggested a multi-pole filter which could
> give the same effective filtering, and could use three small SMT
> inductors. I gathered even that was too big. And I suppose coaxial
> ceramic resonators for one-off projects at 18MHz aren't very
> practical...
>
> > On one extreme, one uses standard LC parts and get fair Qs in small
> > size.
> > On the other extreme, one makes a ersonant cavity to get very high Qs
> > at the expense of size.
> > In between there is something that can be called either a "shielded
> > inductor" or a "resonant cavity with slow wave structure".
>
> There seems to be a popular misconception that a helical resonator
> gives better Q than an unshielded coil and capacitor. One of the key
> nice things about helical resonators is that they are well
> shielded...there's extremely little external field. That lets you
> stack several of them side-by-side, with appropriately chosen coupling
> apertures between the cavities, to make a nice, compact multi-pole
> filter. But let's not assign a quality that isn't there: the same
> coil WITHOUT the shield will have a higher Qu, so long as it's not so
> huge that radiation is a significant loss mechanism, and as Reg
> suggests, that's BIG for most of the tanks we think about. In the
> older editions of "Reference Data for Radio Engineers," e.g. the fifth
> edition, there are some design nomographs for helical resonators in
> the Transmission Lines chapter. They will give you the Qu. If you
> find the Qu of the coil in air (see the same book, Fundamentals of
> Networks chapter, or use Reg's coil program or WAIRCOIL), you'll see
> that the coil's Qu is higher. And if you look also in the Fund. of
> Networks chapter, you'll find a graph for the decrease of inductance
> of a coil when shielded, and you'll find that that almost exactly
> accounts for the Q lowering: same effective series resistance, but
> lower inductance, gives lower Q. Is it significant? Well, I think
> for a typical helical resonator, it's a 15% to 25% lowering.
>
> Mainly I want to dispell the notion that a helical resonator is
> something magic that _raises_ the Q of a given coil, because it's not.
> It does have some very nice properties, but that just isn't one of
> them.
>
> Early helical resonator reference: W. W. Macalpine and R. O.
> Schildknecht, "Coaxial Resonators with Helical Inner Conductor," Proc.
> of the IRE, Dec. 1959 -- almost 45 years ago now.
>
> Cheers,
> Tom

Yes, but the emphasis was on small size, and a helical resonator
allows a goodly shrinkage of volume wihout a corresponding loss large of
Q.
But if the frequency is low enough, the ferite core method, if
properly wound, then becomes a "preferred" solution for small size and
high Q.
Maybe his requirements are not too realistic?

[Robert Baer]

Scott Stephens wrote:
>
> Robert Baer wrote:
>
> > Paul Burridge wrote:
> >
> >>On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> > wrote:
> >>
> >>
> >>>An 8 MHz filter doesn't have to be physically large Paul,
> >>
> >>Hi Q coils in that frequency range in compact sizes... they don't seem
> >>to go together. :-(
>
> > A high Q resonant circuit can be rather small.
> > For example, i made a tunable LC with a Q approaching 1000, and it was
> > not the size of a garbage can (resonant cavity); it was about 5 inches
> > tall and about 3 inches in diameter.
>
> That doesn't sound very small.
>
> > On one extreme, one uses standard LC parts and get fair Qs in small
> > size.
>
> You can also use positive feedback (negative resistance) to sharpen Q,
> if you are somewhat careful or don't mind tweaking.
>
> > Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
> > desigh equations.
> > The terminology used was "Helical resonator".
>
> The ARRL Handbook has/had a design table for them too.
>
> --
> Scott
>
> **********************************
>
> DIY Piezo-Gyro, PCB Drill Bot & More Soon!
>
> http://home.comcast.net/~scottxs/
>
> **********************************

A resonant cavity for the FM band would be roughly the size of a
garbage can (which i stated); 6 inches is slightly smaller, i think.

[Robert Baer]

Scott Stephens wrote:
>
> Robert Baer wrote:
>
> > Paul Burridge wrote:
> >
> >>On Wed, 14 Apr 2004 00:36:17 GMT, "Harold E. Johnson"
> > wrote:
> >>
> >>
> >>>An 8 MHz filter doesn't have to be physically large Paul,
> >>
> >>Hi Q coils in that frequency range in compact sizes... they don't seem
> >>to go together. :-(
>
> > A high Q resonant circuit can be rather small.
> > For example, i made a tunable LC with a Q approaching 1000, and it was
> > not the size of a garbage can (resonant cavity); it was about 5 inches
> > tall and about 3 inches in diameter.
>
> That doesn't sound very small.
>
> > On one extreme, one uses standard LC parts and get fair Qs in small
> > size.
>
> You can also use positive feedback (negative resistance) to sharpen Q,
> if you are somewhat careful or don't mind tweaking.
>
> > Rather ingenious; ther was an IEE paper 20 years(??) ago covering the
> > desigh equations.
> > The terminology used was "Helical resonator".
>
> The ARRL Handbook has/had a design table for them too.
>
> --
> Scott
>
> **********************************
>
> DIY Piezo-Gyro, PCB Drill Bot & More Soon!
>
> http://home.comcast.net/~scottxs/
>
> **********************************

A resonant cavity for the FM band would be roughly the size of a
garbage can (which i stated); 6 inches is slightly smaller, i think.

[James Meyer]

On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
this:

>John Larkin wrote:
>>
>>
>> Well, all the usual methods: resonance width, phase shift, ringdown,
>> stuff like that. I work with gadgets with Qs over 1e9, and people
>> measure them without difficulty.
>>
>> John
>
> Ringdown is the easist way when Qs are extremely high.

You must still account for the energy you extract from the circuit in
order to measure the ringdown. Even the energy needed to drive a high impedance
probe is significant when the Q gets high.

IOW, the Q without the probe will be higher than the Q when you insert
the probe to measure the Q.

Jim

[James Meyer]

On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
this:

>John Larkin wrote:
>>
>>
>> Well, all the usual methods: resonance width, phase shift, ringdown,
>> stuff like that. I work with gadgets with Qs over 1e9, and people
>> measure them without difficulty.
>>
>> John
>
> Ringdown is the easist way when Qs are extremely high.

You must still account for the energy you extract from the circuit in
order to measure the ringdown. Even the energy needed to drive a high impedance
probe is significant when the Q gets high.

IOW, the Q without the probe will be higher than the Q when you insert
the probe to measure the Q.

Jim

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
> IOW, the Q without the probe will be higher than the Q when you insert
>the probe to measure the Q.

Use an inductive current pick-off. That how the Marconi Instruments 1245
series Q-meters work(ed).
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
> IOW, the Q without the probe will be higher than the Q when you insert
>the probe to measure the Q.

Use an inductive current pick-off. That how the Marconi Instruments 1245
series Q-meters work(ed).
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Larkin]

On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
>this:
>
>>John Larkin wrote:
>>>
>>>
>>> Well, all the usual methods: resonance width, phase shift, ringdown,
>>> stuff like that. I work with gadgets with Qs over 1e9, and people
>>> measure them without difficulty.
>>>
>>> John
>>
>> Ringdown is the easist way when Qs are extremely high.
>
> You must still account for the energy you extract from the circuit in
>order to measure the ringdown. Even the energy needed to drive a high impedance
>probe is significant when the Q gets high.
>
> IOW, the Q without the probe will be higher than the Q when you insert
>the probe to measure the Q.
>
>Jim
>

Of course, you can account for the probe loss when you do the math. Or
leave the probe disconnected during a ringdown, and add it after some
delay to see how much energy is left in the system.

John

[John Larkin]

On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
>this:
>
>>John Larkin wrote:
>>>
>>>
>>> Well, all the usual methods: resonance width, phase shift, ringdown,
>>> stuff like that. I work with gadgets with Qs over 1e9, and people
>>> measure them without difficulty.
>>>
>>> John
>>
>> Ringdown is the easist way when Qs are extremely high.
>
> You must still account for the energy you extract from the circuit in
>order to measure the ringdown. Even the energy needed to drive a high impedance
>probe is significant when the Q gets high.
>
> IOW, the Q without the probe will be higher than the Q when you insert
>the probe to measure the Q.
>
>Jim
>

Of course, you can account for the probe loss when you do the math. Or
leave the probe disconnected during a ringdown, and add it after some
delay to see how much energy is left in the system.

John

[Tom Bruhns]

Robert Baer > wrote in message >...
....
> Yes, but the emphasis was on small size, and a helical resonator
> allows a goodly shrinkage of volume wihout a corresponding loss large of
> Q.

As compared with what? A given coil in a helical resonator will
result in lower Qu than that same coil unshielded and simply resonated
with a good capacitor.


....
> Maybe his requirements are not too realistic?

Seems to commonly be the case.

[Tom Bruhns]

Robert Baer > wrote in message >...
....
> Yes, but the emphasis was on small size, and a helical resonator
> allows a goodly shrinkage of volume wihout a corresponding loss large of
> Q.

As compared with what? A given coil in a helical resonator will
result in lower Qu than that same coil unshielded and simply resonated
with a good capacitor.


....
> Maybe his requirements are not too realistic?

Seems to commonly be the case.

[James Meyer]

On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>
>Use an inductive current pick-off. That how the Marconi Instruments 1245
>series Q-meters work(ed).

Nevertheless, *ANY* method used to probe the field associated with the
resonator will load the resonator and degrade the Q.

Jim

[James Meyer]

On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>
>Use an inductive current pick-off. That how the Marconi Instruments 1245
>series Q-meters work(ed).

Nevertheless, *ANY* method used to probe the field associated with the
resonator will load the resonator and degrade the Q.

Jim

[James Meyer]

On Sat, 17 Apr 2004 10:04:36 -0700, John Larkin
> posted this:

>On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
>wrote:
>
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>>
>>Jim
>>
>
>Of course, you can account for the probe loss when you do the math. Or
>leave the probe disconnected during a ringdown, and add it after some
>delay to see how much energy is left in the system.
>
>John

If you have to "do the math", you might as well just calculate the Q
from first principles and forget the "measurement".

Jim

[James Meyer]

On Sat, 17 Apr 2004 10:04:36 -0700, John Larkin
> posted this:

>On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
>wrote:
>
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>>
>>Jim
>>
>
>Of course, you can account for the probe loss when you do the math. Or
>leave the probe disconnected during a ringdown, and add it after some
>delay to see how much energy is left in the system.
>
>John

If you have to "do the math", you might as well just calculate the Q
from first principles and forget the "measurement".

Jim

[James Meyer]

On 17 Apr 2004 10:09:22 -0700, (Tom Bruhns) posted this:

>Robert Baer > wrote in message >...
>...
>> Yes, but the emphasis was on small size, and a helical resonator
>> allows a goodly shrinkage of volume wihout a corresponding loss large of
>> Q.
>
>As compared with what? A given coil in a helical resonator will
>result in lower Qu than that same coil unshielded and simply resonated
>with a good capacitor.
>
>
Not so. And others have pointed that out. If you take an unshielded
coil to it's ultimate configuration you are confronted with a resonant antenna
that is loaded by its radiation resistance and that results in a *lower* Q than
a properly shielded resonator.

Jim

[James Meyer]

On 17 Apr 2004 10:09:22 -0700, (Tom Bruhns) posted this:

>Robert Baer > wrote in message >...
>...
>> Yes, but the emphasis was on small size, and a helical resonator
>> allows a goodly shrinkage of volume wihout a corresponding loss large of
>> Q.
>
>As compared with what? A given coil in a helical resonator will
>result in lower Qu than that same coil unshielded and simply resonated
>with a good capacitor.
>
>
Not so. And others have pointed that out. If you take an unshielded
coil to it's ultimate configuration you are confronted with a resonant antenna
that is loaded by its radiation resistance and that results in a *lower* Q than
a properly shielded resonator.

Jim

[John Larkin]

On Sat, 17 Apr 2004 19:07:12 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 10:04:36 -0700, John Larkin
> posted this:
>
>>On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
>>wrote:
>>
>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>the probe to measure the Q.
>>>
>>>Jim
>>>
>>
>>Of course, you can account for the probe loss when you do the math. Or
>>leave the probe disconnected during a ringdown, and add it after some
>>delay to see how much energy is left in the system.
>>
>>John
>
> If you have to "do the math", you might as well just calculate the Q
>from first principles and forget the "measurement".
>
>Jim


How can you calculate Q from first principles? 3D EM simulation?
Quantum mechanics?

John

[John Larkin]

On Sat, 17 Apr 2004 19:07:12 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 10:04:36 -0700, John Larkin
> posted this:
>
>>On Sat, 17 Apr 2004 15:46:59 GMT, James Meyer >
>>wrote:
>>
>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>the probe to measure the Q.
>>>
>>>Jim
>>>
>>
>>Of course, you can account for the probe loss when you do the math. Or
>>leave the probe disconnected during a ringdown, and add it after some
>>delay to see how much energy is left in the system.
>>
>>John
>
> If you have to "do the math", you might as well just calculate the Q
>from first principles and forget the "measurement".
>
>Jim


How can you calculate Q from first principles? 3D EM simulation?
Quantum mechanics?

John

[Roy Lewallen]

Ah, just the person I've been waiting for. How do you account for
current bunching on the conductors (that is, non-uniform distribution of
current around the conductors)? What reference, equation, or program do
you use? Nearly all "first principle" calculations of Q I've seen
grossly overestimate Q, and I believe the failure to take this into
account is at least part of the reason. I haven't seen a decent
analytical method of dealing with it, and an anxious to see how you do it.

Then there's surface corrosion and roughness, radiation, and coupling to
nearby objects. How do you deal with those? Have you identified some of
the other factors that often make a simplistic "first principle"
calculation disagree so badly with carefully made measurements?

Roy Lewallen, W7EL

James Meyer wrote:
>
> If you have to "do the math", you might as well just calculate the Q
> from first principles and forget the "measurement".
>
> Jim
>

[Roy Lewallen]

Ah, just the person I've been waiting for. How do you account for
current bunching on the conductors (that is, non-uniform distribution of
current around the conductors)? What reference, equation, or program do
you use? Nearly all "first principle" calculations of Q I've seen
grossly overestimate Q, and I believe the failure to take this into
account is at least part of the reason. I haven't seen a decent
analytical method of dealing with it, and an anxious to see how you do it.

Then there's surface corrosion and roughness, radiation, and coupling to
nearby objects. How do you deal with those? Have you identified some of
the other factors that often make a simplistic "first principle"
calculation disagree so badly with carefully made measurements?

Roy Lewallen, W7EL

James Meyer wrote:
>
> If you have to "do the math", you might as well just calculate the Q
> from first principles and forget the "measurement".
>
> Jim
>

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>
>>I read in sci.electronics.design that James Meyer >
>>wrote (in >) about 'A neat
>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>the probe to measure the Q.
>>
>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>series Q-meters work(ed).
>
> Nevertheless, *ANY* method used to probe the field associated with the
>resonator will load the resonator and degrade the Q.
>
IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
short length of silver wire, gold-plated to eliminate sulfide attack.
The effect on Q would be minimal in the extreme.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>
>>I read in sci.electronics.design that James Meyer >
>>wrote (in >) about 'A neat
>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>the probe to measure the Q.
>>
>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>series Q-meters work(ed).
>
> Nevertheless, *ANY* method used to probe the field associated with the
>resonator will load the resonator and degrade the Q.
>
IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
short length of silver wire, gold-plated to eliminate sulfide attack.
The effect on Q would be minimal in the extreme.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[Barry Lennox]

On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> wrote:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>
>Use an inductive current pick-off. That how the Marconi Instruments 1245
>series Q-meters work(ed).

I can recall using one of those, some little time back. Anybody have
the schematic diagram for it?

Barry Lennox

[Barry Lennox]

On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> wrote:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>> IOW, the Q without the probe will be higher than the Q when you insert
>>the probe to measure the Q.
>
>Use an inductive current pick-off. That how the Marconi Instruments 1245
>series Q-meters work(ed).

I can recall using one of those, some little time back. Anybody have
the schematic diagram for it?

Barry Lennox

[James Meyer]

On Sat, 17 Apr 2004 12:22:03 -0700, Roy Lewallen > posted this:

>Ah, just the person I've been waiting for. How do you account for
>current bunching on the conductors (that is, non-uniform distribution of
>current around the conductors)? What reference, equation, or program do
>you use? Nearly all "first principle" calculations of Q I've seen
>grossly overestimate Q, and I believe the failure to take this into
>account is at least part of the reason. I haven't seen a decent
>analytical method of dealing with it, and an anxious to see how you do it.
>
>Then there's surface corrosion and roughness, radiation, and coupling to
>nearby objects. How do you deal with those? Have you identified some of
>the other factors that often make a simplistic "first principle"
>calculation disagree so badly with carefully made measurements?
>
>Roy Lewallen, W7EL
>
>James Meyer wrote:
>>
>> If you have to "do the math", you might as well just calculate the Q
>> from first principles and forget the "measurement".
>>
>> Jim
>>

I was responding to a suggestion that one could do the math to calculate
what the Q would have been if you hadn't tried to measure it. I was pointing
out that if you could do that math, and get it correct, that you could do the
whole exercise with math and forget measuring anything.

And how do you know for sure that calculations overestimate Q when
measuring Q to verify the calculations disturbs the very thing you're measuring?

An engineer knows when to say "close enough". A mathematician is never
satisfied.

Jim

[James Meyer]

On Sat, 17 Apr 2004 12:22:03 -0700, Roy Lewallen > posted this:

>Ah, just the person I've been waiting for. How do you account for
>current bunching on the conductors (that is, non-uniform distribution of
>current around the conductors)? What reference, equation, or program do
>you use? Nearly all "first principle" calculations of Q I've seen
>grossly overestimate Q, and I believe the failure to take this into
>account is at least part of the reason. I haven't seen a decent
>analytical method of dealing with it, and an anxious to see how you do it.
>
>Then there's surface corrosion and roughness, radiation, and coupling to
>nearby objects. How do you deal with those? Have you identified some of
>the other factors that often make a simplistic "first principle"
>calculation disagree so badly with carefully made measurements?
>
>Roy Lewallen, W7EL
>
>James Meyer wrote:
>>
>> If you have to "do the math", you might as well just calculate the Q
>> from first principles and forget the "measurement".
>>
>> Jim
>>

I was responding to a suggestion that one could do the math to calculate
what the Q would have been if you hadn't tried to measure it. I was pointing
out that if you could do that math, and get it correct, that you could do the
whole exercise with math and forget measuring anything.

And how do you know for sure that calculations overestimate Q when
measuring Q to verify the calculations disturbs the very thing you're measuring?

An engineer knows when to say "close enough". A mathematician is never
satisfied.

Jim

[James Meyer]

On Sat, 17 Apr 2004 21:05:34 +0100, John Woodgate
> posted this:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>>
>>>I read in sci.electronics.design that James Meyer >
>>>wrote (in >) about 'A neat
>>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>>the probe to measure the Q.
>>>
>>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>>series Q-meters work(ed).
>>
>> Nevertheless, *ANY* method used to probe the field associated with the
>>resonator will load the resonator and degrade the Q.
>>
>IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
>short length of silver wire, gold-plated to eliminate sulfide attack.
>The effect on Q would be minimal in the extreme.

But what about the energy extracted from the probe to make the
measurement? Any load on the probe is transformed into a load on the resonator.
Compensating for that load requires a very small number be divided by another
very small number. Any error in either number makes a much larger error in the
result of the calculation.

Jim

[James Meyer]

On Sat, 17 Apr 2004 21:05:34 +0100, John Woodgate
> posted this:

>I read in sci.electronics.design that James Meyer >
>wrote (in >) about 'A neat
>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>>
>>>I read in sci.electronics.design that James Meyer >
>>>wrote (in >) about 'A neat
>>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>> IOW, the Q without the probe will be higher than the Q when you insert
>>>>the probe to measure the Q.
>>>
>>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>>series Q-meters work(ed).
>>
>> Nevertheless, *ANY* method used to probe the field associated with the
>>resonator will load the resonator and degrade the Q.
>>
>IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
>short length of silver wire, gold-plated to eliminate sulfide attack.
>The effect on Q would be minimal in the extreme.

But what about the energy extracted from the probe to make the
measurement? Any load on the probe is transformed into a load on the resonator.
Compensating for that load requires a very small number be divided by another
very small number. Any error in either number makes a much larger error in the
result of the calculation.

Jim

[Roy Lewallen]

James Meyer wrote:
> . . .
> And how do you know for sure that calculations overestimate Q when
> measuring Q to verify the calculations disturbs the very thing you're measuring?
>
> An engineer knows when to say "close enough". A mathematician is never
> satisfied.
>

I've measured quite a number of inductors both with a homebrew setup, in
which I account for the losses in the input and output networks, and
with an HP Q meter of specified accuracy. With simple input and output
networks consisting of a small series C and shunt R, the effect on Q is
predictable and easy to calculate. Results from the two methods agree
quite closely, even though they use somewhat different methods to arrive
at the Q, giving a fair amount of confidence in both results. And both
disagree quite dramatically in some cases to Q calculated simply from
theoretical calculations which include only conductor resistance
(including skin effect, of course), inductance, and shunt capacitance.
This is with inductors of only moderate Q -- calculation of very high Q
inductors, which is being discussed here, would require more attention
to second order effects -- as would measurement.

Thanks for the profound observation about mathematicians and engineers.
In which category does one put a person who's satisfied with
calculations made without thinking about, caring about, or considering
the errors caused by ignoring fundamental effects? Certainly not an
engineer as I use the term.

Roy Lewallen, W7EL

[Roy Lewallen]

James Meyer wrote:
> . . .
> And how do you know for sure that calculations overestimate Q when
> measuring Q to verify the calculations disturbs the very thing you're measuring?
>
> An engineer knows when to say "close enough". A mathematician is never
> satisfied.
>

I've measured quite a number of inductors both with a homebrew setup, in
which I account for the losses in the input and output networks, and
with an HP Q meter of specified accuracy. With simple input and output
networks consisting of a small series C and shunt R, the effect on Q is
predictable and easy to calculate. Results from the two methods agree
quite closely, even though they use somewhat different methods to arrive
at the Q, giving a fair amount of confidence in both results. And both
disagree quite dramatically in some cases to Q calculated simply from
theoretical calculations which include only conductor resistance
(including skin effect, of course), inductance, and shunt capacitance.
This is with inductors of only moderate Q -- calculation of very high Q
inductors, which is being discussed here, would require more attention
to second order effects -- as would measurement.

Thanks for the profound observation about mathematicians and engineers.
In which category does one put a person who's satisfied with
calculations made without thinking about, caring about, or considering
the errors caused by ignoring fundamental effects? Certainly not an
engineer as I use the term.

Roy Lewallen, W7EL

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>On Sat, 17 Apr 2004 21:05:34 +0100, John Woodgate
> posted this:
>
>>I read in sci.electronics.design that James Meyer >
>>wrote (in >) about 'A neat
>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>>>
>>>>I read in sci.electronics.design that James Meyer >
>>>>wrote (in >) about 'A neat
>>>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>>> IOW, the Q without the probe will be higher than the Q when you
>insert
>>>>>the probe to measure the Q.
>>>>
>>>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>>>series Q-meters work(ed).
>>>
>>> Nevertheless, *ANY* method used to probe the field associated with the
>>>resonator will load the resonator and degrade the Q.
>>>
>>IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
>>short length of silver wire, gold-plated to eliminate sulfide attack.
>>The effect on Q would be minimal in the extreme.
>
> But what about the energy extracted from the probe to make the
>measurement?

The sensing inductor was connected to the grid of a triode tube, with,
IIRC, a 1 Mohm grid leak. With 1 mV across the sensor, that's a whole
1 uJ/s of energy extraction.

>Any load on the probe is transformed into a load on the resonator.
>Compensating for that load requires a very small number be divided by another
>very small number. Any error in either number makes a much larger error in the
>result of the calculation.
>
Check your math. It's small errors in *differences*, not in ratios, that
result in large errors in results.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>On Sat, 17 Apr 2004 21:05:34 +0100, John Woodgate
> posted this:
>
>>I read in sci.electronics.design that James Meyer >
>>wrote (in >) about 'A neat
>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
> posted this:
>>>
>>>>I read in sci.electronics.design that James Meyer >
>>>>wrote (in >) about 'A neat
>>>>and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
>>>>> IOW, the Q without the probe will be higher than the Q when you
>insert
>>>>>the probe to measure the Q.
>>>>
>>>>Use an inductive current pick-off. That how the Marconi Instruments 1245
>>>>series Q-meters work(ed).
>>>
>>> Nevertheless, *ANY* method used to probe the field associated with the
>>>resonator will load the resonator and degrade the Q.
>>>
>>IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
>>short length of silver wire, gold-plated to eliminate sulfide attack.
>>The effect on Q would be minimal in the extreme.
>
> But what about the energy extracted from the probe to make the
>measurement?

The sensing inductor was connected to the grid of a triode tube, with,
IIRC, a 1 Mohm grid leak. With 1 mV across the sensor, that's a whole
1 uJ/s of energy extraction.

>Any load on the probe is transformed into a load on the resonator.
>Compensating for that load requires a very small number be divided by another
>very small number. Any error in either number makes a much larger error in the
>result of the calculation.
>
Check your math. It's small errors in *differences*, not in ratios, that
result in large errors in results.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[Robert Baer]

James Meyer wrote:
>
> On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
> this:
>
> >John Larkin wrote:
> >>
> >>
> >> Well, all the usual methods: resonance width, phase shift, ringdown,
> >> stuff like that. I work with gadgets with Qs over 1e9, and people
> >> measure them without difficulty.
> >>
> >> John
> >
> > Ringdown is the easist way when Qs are extremely high.
>
> You must still account for the energy you extract from the circuit in
> order to measure the ringdown. Even the energy needed to drive a high impedance
> probe is significant when the Q gets high.
>
> IOW, the Q without the probe will be higher than the Q when you insert
> the probe to measure the Q.
>
> Jim

Not a problem; use two different loads.
Just like measuring the internal resistance of a battery or a curent
meter...
...Never done directly.

[Robert Baer]

James Meyer wrote:
>
> On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer > posted
> this:
>
> >John Larkin wrote:
> >>
> >>
> >> Well, all the usual methods: resonance width, phase shift, ringdown,
> >> stuff like that. I work with gadgets with Qs over 1e9, and people
> >> measure them without difficulty.
> >>
> >> John
> >
> > Ringdown is the easist way when Qs are extremely high.
>
> You must still account for the energy you extract from the circuit in
> order to measure the ringdown. Even the energy needed to drive a high impedance
> probe is significant when the Q gets high.
>
> IOW, the Q without the probe will be higher than the Q when you insert
> the probe to measure the Q.
>
> Jim

Not a problem; use two different loads.
Just like measuring the internal resistance of a battery or a curent
meter...
...Never done directly.

[Tom Bruhns]

James Meyer > wrote in message >...
> On 17 Apr 2004 10:09:22 -0700, (Tom Bruhns) posted this:
>
> >Robert Baer > wrote in message >...
> >...
> >> Yes, but the emphasis was on small size, and a helical resonator
> >> allows a goodly shrinkage of volume wihout a corresponding loss large of
> >> Q.
> >
> >As compared with what? A given coil in a helical resonator will
> >result in lower Qu than that same coil unshielded and simply resonated
> >with a good capacitor.
> >
> >
> Not so. And others have pointed that out. If you take an unshielded
> coil to it's ultimate configuration you are confronted with a resonant antenna
> that is loaded by its radiation resistance and that results in a *lower* Q than
> a properly shielded resonator.

ONLY if it's really big. See Reg's posting in this thread on that
subject. We're talking about making things small here, like smaller
than a 1 inch diameter coil at 18MHz. The cavity for a standard
helical resonator design will ding the Q by 15% or more; for such a
small unshielded coil do you expect that much radiation? I don't.
Not even close.

Cheers,
Tom

[Tom Bruhns]

James Meyer > wrote in message >...
> On 17 Apr 2004 10:09:22 -0700, (Tom Bruhns) posted this:
>
> >Robert Baer > wrote in message >...
> >...
> >> Yes, but the emphasis was on small size, and a helical resonator
> >> allows a goodly shrinkage of volume wihout a corresponding loss large of
> >> Q.
> >
> >As compared with what? A given coil in a helical resonator will
> >result in lower Qu than that same coil unshielded and simply resonated
> >with a good capacitor.
> >
> >
> Not so. And others have pointed that out. If you take an unshielded
> coil to it's ultimate configuration you are confronted with a resonant antenna
> that is loaded by its radiation resistance and that results in a *lower* Q than
> a properly shielded resonator.

ONLY if it's really big. See Reg's posting in this thread on that
subject. We're talking about making things small here, like smaller
than a 1 inch diameter coil at 18MHz. The cavity for a standard
helical resonator design will ding the Q by 15% or more; for such a
small unshielded coil do you expect that much radiation? I don't.
Not even close.

Cheers,
Tom

[James Meyer]

On Sat, 17 Apr 2004 18:56:14 -0700, Roy Lewallen > posted this:


>Thanks for the profound observation about mathematicians and engineers.
>In which category does one put a person who's satisfied with
>calculations made without thinking about, caring about, or considering
>the errors caused by ignoring fundamental effects? Certainly not an
>engineer as I use the term.
>
>Roy Lewallen, W7EL

Such a person as you describe is commonly known as a physicist. I have
had to work with several. That some of them are still alive is a testament to
my degree of self control.

Jim

[James Meyer]

On Sat, 17 Apr 2004 18:56:14 -0700, Roy Lewallen > posted this:


>Thanks for the profound observation about mathematicians and engineers.
>In which category does one put a person who's satisfied with
>calculations made without thinking about, caring about, or considering
>the errors caused by ignoring fundamental effects? Certainly not an
>engineer as I use the term.
>
>Roy Lewallen, W7EL

Such a person as you describe is commonly known as a physicist. I have
had to work with several. That some of them are still alive is a testament to
my degree of self control.

Jim

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sun, 18 Apr 2004:
>On Sat, 17 Apr 2004 18:56:14 -0700, Roy Lewallen > posted this:
>
>
>>Thanks for the profound observation about mathematicians and engineers.
>>In which category does one put a person who's satisfied with
>>calculations made without thinking about, caring about, or considering
>>the errors caused by ignoring fundamental effects? Certainly not an
>>engineer as I use the term.
>>
>>Roy Lewallen, W7EL
>
> Such a person as you describe is commonly known as a physicist. I have
>had to work with several. That some of them are still alive is a testament to
>my degree of self control.
>
LOL! But physicists are usually *preoccupied* with fundamental effects
and tend to ignore others.

In my brief skirmish with aeronautical engineering, I formed the opinion
that most of the calculations were as pragmatic as RL suggests; the only
consolation is that they seem to work.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Woodgate]

I read in sci.electronics.design that James Meyer >
wrote (in >) about 'A neat
and compact way to generate RF harmonics...', on Sun, 18 Apr 2004:
>On Sat, 17 Apr 2004 18:56:14 -0700, Roy Lewallen > posted this:
>
>
>>Thanks for the profound observation about mathematicians and engineers.
>>In which category does one put a person who's satisfied with
>>calculations made without thinking about, caring about, or considering
>>the errors caused by ignoring fundamental effects? Certainly not an
>>engineer as I use the term.
>>
>>Roy Lewallen, W7EL
>
> Such a person as you describe is commonly known as a physicist. I have
>had to work with several. That some of them are still alive is a testament to
>my degree of self control.
>
LOL! But physicists are usually *preoccupied* with fundamental effects
and tend to ignore others.

In my brief skirmish with aeronautical engineering, I formed the opinion
that most of the calculations were as pragmatic as RL suggests; the only
consolation is that they seem to work.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

[John Larkin]

On Sat, 17 Apr 2004 23:48:01 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 12:22:03 -0700, Roy Lewallen > posted this:
>
>>Ah, just the person I've been waiting for. How do you account for
>>current bunching on the conductors (that is, non-uniform distribution of
>>current around the conductors)? What reference, equation, or program do
>>you use? Nearly all "first principle" calculations of Q I've seen
>>grossly overestimate Q, and I believe the failure to take this into
>>account is at least part of the reason. I haven't seen a decent
>>analytical method of dealing with it, and an anxious to see how you do it.
>>
>>Then there's surface corrosion and roughness, radiation, and coupling to
>>nearby objects. How do you deal with those? Have you identified some of
>>the other factors that often make a simplistic "first principle"
>>calculation disagree so badly with carefully made measurements?
>>
>>Roy Lewallen, W7EL
>>
>>James Meyer wrote:
>>>
>>> If you have to "do the math", you might as well just calculate the Q
>>> from first principles and forget the "measurement".
>>>
>>> Jim
>>>
>
> I was responding to a suggestion that one could do the math to calculate
>what the Q would have been if you hadn't tried to measure it. I was pointing
>out that if you could do that math, and get it correct, that you could do the
>whole exercise with math and forget measuring anything.
>

The math in question is trivial. Qs from 1 to 1e9 can be measured
accurately without difficulty.

>
> An engineer knows when to say "close enough". A mathematician is never
>satisfied.

But then, mathematicians don't measure things, do they?

John

[John Larkin]

On Sat, 17 Apr 2004 23:48:01 GMT, James Meyer >
wrote:

>On Sat, 17 Apr 2004 12:22:03 -0700, Roy Lewallen > posted this:
>
>>Ah, just the person I've been waiting for. How do you account for
>>current bunching on the conductors (that is, non-uniform distribution of
>>current around the conductors)? What reference, equation, or program do
>>you use? Nearly all "first principle" calculations of Q I've seen
>>grossly overestimate Q, and I believe the failure to take this into
>>account is at least part of the reason. I haven't seen a decent
>>analytical method of dealing with it, and an anxious to see how you do it.
>>
>>Then there's surface corrosion and roughness, radiation, and coupling to
>>nearby objects. How do you deal with those? Have you identified some of
>>the other factors that often make a simplistic "first principle"
>>calculation disagree so badly with carefully made measurements?
>>
>>Roy Lewallen, W7EL
>>
>>James Meyer wrote:
>>>
>>> If you have to "do the math", you might as well just calculate the Q
>>> from first principles and forget the "measurement".
>>>
>>> Jim
>>>
>
> I was responding to a suggestion that one could do the math to calculate
>what the Q would have been if you hadn't tried to measure it. I was pointing
>out that if you could do that math, and get it correct, that you could do the
>whole exercise with math and forget measuring anything.
>

The math in question is trivial. Qs from 1 to 1e9 can be measured
accurately without difficulty.

>
> An engineer knows when to say "close enough". A mathematician is never
>satisfied.

But then, mathematicians don't measure things, do they?

John

[Don Young]

John,
Are you saying you have some SRDs available?
I could use a couple in a GPR I'm working on.
Part of the Sample pulse generator.
Don

John Larkin wrote:

> On Mon, 12 Apr 2004 19:09:51 GMT, "Harold E. Johnson"
> > wrote:
>
>
>>>If you do use diodes for higher-order harmonic generation, and not
>>>just a simple full-wave-rectifier type frequency doubler, I suppose
>>>you want something of the nature of a step recovery diode. That
>>>implies minority carrier stored charge in the diode, and that would
>>>preclude using a Schottky diode (which would work great in the
>>>full-wave-rectifier type doubler). If you get into actually wanting
>>>to generate harmonic combs out to microwave frequencies, it's probably
>>>worthwhile looking for diodes actually characterized for step recovery
>>>service. But I really think that's way beyond what you are trying to
>>>accomplish right now.
>>>
>>My turn to learn something here. Tom, would you elaborate a bit on the above
>>please? I know SRD's are comb generators out to visible light, but they're
>>also 50 percent hard to find and 50 percent magic. I've been using
>>Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
>>promising myself that I'm gonna substitute an MMIC for that one day, I DID
>>find the "Filter Gain" in the line length from generator to filter), THAT
>>was both impressive AND helpful. If I go with the MMIC, any preference of
>>Silicon over GaAs?
>>
>>Regards
>>
>>W4ZCB
>>
>>
>
> The only distributor-stock SRDs I know of are the M/Acom MA44767,
> MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
> carries them. The '68 or '69 should be good for multiplication to 2
> GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
> There are lots of appnotes around about using them as multipliers.
>
> I have a bunch in stock and can send a few to anybody who wants to
> play.
>
> John
>
>


--
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