"Steve Nosko" wrote in message ...

Side bar: I have one of the first directional power meters, the Micro
match. It uses a resistor, yes, resistor, for the current sense rather than
the now common current transformer toroid. circa 1945 -50.

Not really all that uncommon. A Wheatstone bridge works fine for
monitoring SWR, and transformer-coupled versions of essentially a
Wheatstone bridge are commonly used in S-parameter test sets used with
network analyzers. Nice for flat response over lots of octaves, if
you are verrrry careful about the construction.


You might think of microstrip or stripline as "hammered flat coax."
:-)

The accepted terminology is "Stripline" (think "strip transmission
line") for the line with two flat ground planes on either side of the
"center conductor" which can be thought of as this flattened coax....and
"micro strip" ( I have no memory aid) for the one that is one-sided where
the "center conductor" is on the top of a PCB with a ground plane on the
bottom..

(And though stripline is true TEM, microstrip is quasi-TEM because of
the different dielectric above and below the microstrip.)

It is just a transmission line on a PCB, the characteristic impedance
dependent on trace line width, thickness of the foil, dielectric
constant
of the PCB material and, to some extent, the thickness of the PCB.

I think the PCB material (thickness & properties) has a larger
contribution to the Zo that the runner thickness...at least at the freqs I
worked at (1GHz.). Good ole' Wheeler & Sobol equations for the Zo.

Yep, by far. The free "RFSim99" program will help with the dimensions
for five different kinds of couplers, you pick the coupling, including
stripline and microstrip. The one thing it fails to mention is the
1/4 wave line length for the given coupling.


Directional couplers are simply a quarter wavelength of transmission
line (coax or microstrip or stripline) that runs parallel to the main
line
connecting to the antenna.

I believe a 1/4 wave is not important here.

Right...but beware of NULLS in the response at integer multiples of
1/2 wavelength, and the response returns to the same value at 3/4 wave
as it was at 1/4 wave. They are broadly rounded peaks, as Len says
useful over perhaps an octave for non-precision power measurements.
This can be used to advantage for a 146-440MHz coupler: make it 1/4
wave at 146, and it will respond fine at 3/4 wave at 440. But 1/4
wave (even with the 0.5 VF of glass-epoxy circuit board mtrl) is a bit
long. But...you can fold that in a "U" and get it down to ten inches
or so board length.

For broader bandwidth, it's common to make the stripline or microstrip
in three (or five, or...) sections with varying coupling. The center
section is highest coupling, and the outer sections are lower. You
can find design info on the web about this. The broadening is quite
significant.

....
Typical directional coupler coupling is 20 db down from the main line.

This is a matter of choice by the manufacturer construction. What this
means is that the power coming out the (correct end of the) secondary line
is 20dB down (1/100 th) from the power on the main line.

In fact, -20dB with 100 watts input gives you a WATT at the "FWD"
output, which is WAY more than I want to deal with! Simple diode
detectors let me "see" down to -50dBm, so even a milliwatt is really
more than I need. Even with 10mW of excitation, a -30dB coupler is
quite useful. DESIGN the coupler to give you what you want at the
output!


While not perfect, directional
coupling differences of about 20 db are good enough to warrant the
name "directional."

This is a matter of primarily the mechanical design.

AND the loading on the "other" end of the coupled line. Steve touched
on this, but I think it deserves more emphasis. Consider: if you have
a -20dB coupler and 100 watts forward and zero return on the "through"
line, you have a watt trying to come out the "forward" coupled port.
If you don't terminate that perfectly, some of that watt goes back the
other way, and spoils the directionality. SO...if you screwed up the
trace width (perhaps because you didn't know the dielectric constant
or thickness of the board material exactly, or your etching wasn't
perfect), you can still adjust for very nearly perfect directivity by
adjusting the load on the coupled line. This is also why it's good,
especially at microwaves, to NOT try to use two detectors on opposite
ends of the same coupled line, because the detectors are more
difficult to have be really good resistances and not introduce
parasitic reactance. One way to make the load adjustable (assuming
low enough coupled power that you can use SMT resistors) would be to
provide pads for multiple termination resistors (two or three) and use
a parallel combination that gives you just the right termination.
This assumes you have a really good load (including any line and
fittings) you can put on the through-line to insure near-zero
reflections there! Calibration-quality loads for GHz frequencies are
NOT cheap, and garden-variety coax is practically guaranteed to NOT be
50 ohms exactly. (45-55 is about the best reasonable expectation you
should have for RG-58.)

....

Cheers,
Tom

WARNING
LONG WINDED POST BY TWO OLD FOGEYS...

Did I spell that correctly?

"Avery Fineman" wrote in message
...
In article , "Steve Nosko"
writes:

More snipping of a good post to avoid undue long length...
But I see we both are having trouble with the length, eh Len?


The accepted terminology is "Stripline" [snip] and "micro strip" ...

That's quite probably true. ..some in the RF field get over-wrought
about terminology....
Either type of physical construction makes a TEM (Transverse
ElectroMagnetic) transmission line, just like coaxial cable....

Not getting religious about it, just adding some info here & trying to
clarify/simplify the explanatin. The OP asked if the "Directional coupler"
being talked about was like the Moni-Match. I was just trying to make that
case---then, as is common here, to add a lot of stuff I felt was helpful in
explaining what I thought the OP _may_ want to know...if he/she didn't give
up on the long post hi hi


I believe a 1/4 wave is not important here.
For an octave bandwidth and even coupling it is.
...If the object to obtain a low phase error...

I didn't think the OP was asking about octave bandwidth or phase.
Perhaps I missed that.


ANY conductor running close to and parallel to a transmission line
center conductor will couple something into the coupling line.

That's the idea I was trying to point out. Like What I call the "snaked
wire" version.



Then we get into deeper detail and possibly symmantics. I'll keep my
symmantics comments to a minimum since I was simply trying to provide a
simplified comparison with the monimatch and a little info on how they work.

Typical directional coupler coupling is 20 db down from the main
line.
This is a matter of choice by the manufacturer construction.
I'll say that it is a value chosen by the users...manufacturers make
all kinds of coupler coupling values

And I meant that when a given coupling is desired, it is the physical
construction which gets you there.

...With 20 db coupling ...,
the main line is hardly affected whether the coupled line is terminated
in proper resistive value or open or shorted.

Sure. Weather or not you pull 1% of the power out, few of us will care.


name "directional."
This is a matter of primarily the mechanical design.
Mechanical AND electrical...that also influences the directivity.

Again, I was merely pointing out that good construction is necessary for
good directivity. In contrast to the "snaked" coax version which can have
highly variable performance.


The "directivity"
refers to the amount of power that gets coupled to the secondary line
that
emerges out the "wrong" end--not the one we want.

"Directivity" values are the sum of forward coupling and reverse
coupling. If a coupler has 20 db coupling and the directivity is
45 db, the reverse coupling is down 25 db. ...

I presume you intend to mean"...from the foward _coupled_ level." ???
This is what I was trying to say.

And don't forget conservation of energy. ...
At 20 db coupling, a bad coupled line termination results in a 1%



Probably going too far for the OP's original need I guess I'm just as
guilty of adding mounds of information that he OP might not be interestred
in.

They both should have a nice (50 ohm) impedance ...
Only if that is the main line characteristic impedance being used.
That's why I put the 50 in (), just as an example. I should have left
it out, but then I figured a question of "what is 'nice'" might have
surfaced.


...For the Moni-Match (snaked type) the secondary lines could be
some weird Zo and all is well if it is matched pretty well.
But...the amount of coupling CAN vary considerably with frequency
even though direction of coupling has an good relative agreement.

Sure. Again, I don't thing the OP is worried about flat freq response.
Many of us are familiar with the switched SWR meter with the pot to set the
FWD power to full scale and how that varies from band to band. We live with
it. At work, however, flat couplers are needed.
In fact, I was doing it last night. Was puzeled by the worse SWR on
teh lower bands of a high quality load. Could be... the SWR meter..
..

I'll base that on measuring the "snaked-through-the-large-coax" kind
(two different versions) intended for higher HF bands that had about
15 db difference between the two of them AND had quite a variation
in coupling over frequency.

Do you remember if you looked at the Zo of the coupled lines? I seem to
recall that in the articles, the termination of the coupled line is
considered an emperical optimization. cut-try for the value of load giving
"best" operation. I also wondered about the load seen at the end(s) where
the detectors were. Did they get a good match there. That;s going to mess
with your directivity, no? I guess you can put a good load on the main line
and just tweek for best directivity... a.k.a. lowest reading when line
matched - in BOTH directions. Seems that this is all you need to worry
about, for a ham, that is.


To make duplicates of an article's presentation requires a slavish
devotion to copying EXACTLY as described.

Again, that's where my comment about mechanigal construction came from.

By the way, you can pump power into the secondary line and have some come
out the mainline as well. This is actually done for special uses.
3 db couplers, also known as "hybrid couplers." Very good for making
wideband push-pull or push-push amplifiers out of modular amplifiers.

Won't go into detail, but high power linear amplifiers (60dB 2 tone IM)
in the 800MHz & 1800MHz range use 20 dB couplers for "Feed-Forward" IM
correction loops. Made an extensive "Backplane" with many stripline
couplers for them.


...High dielectric constant
in substrate allows making them smaller and the material insures
stability and good control in manufacture.
I have used Alumina. I also saw an article on microstrip couplers with
a complementary zig-zag pattern on the edges of the coupled lines adjacent
to each other...forget what the advantage was...I think increased coupling.


...Analog Devices log detector is
I saw that little bugger in QEX. Pretty cool!


73, Len

--
Steve N, K,9;d, c. i My email has no u's.

WARNING
LONG WINDED POST BY TWO OLD FOGEYS...

Did I spell that correctly?

"Avery Fineman" wrote in message
...
In article , "Steve Nosko"
writes:

More snipping of a good post to avoid undue long length...
But I see we both are having trouble with the length, eh Len?


The accepted terminology is "Stripline" [snip] and "micro strip" ...

That's quite probably true. ..some in the RF field get over-wrought
about terminology....
Either type of physical construction makes a TEM (Transverse
ElectroMagnetic) transmission line, just like coaxial cable....

Not getting religious about it, just adding some info here & trying to
clarify/simplify the explanatin. The OP asked if the "Directional coupler"
being talked about was like the Moni-Match. I was just trying to make that
case---then, as is common here, to add a lot of stuff I felt was helpful in
explaining what I thought the OP _may_ want to know...if he/she didn't give
up on the long post hi hi


I believe a 1/4 wave is not important here.
For an octave bandwidth and even coupling it is.
...If the object to obtain a low phase error...

I didn't think the OP was asking about octave bandwidth or phase.
Perhaps I missed that.


ANY conductor running close to and parallel to a transmission line
center conductor will couple something into the coupling line.

That's the idea I was trying to point out. Like What I call the "snaked
wire" version.



Then we get into deeper detail and possibly symmantics. I'll keep my
symmantics comments to a minimum since I was simply trying to provide a
simplified comparison with the monimatch and a little info on how they work.

Typical directional coupler coupling is 20 db down from the main
line.
This is a matter of choice by the manufacturer construction.
I'll say that it is a value chosen by the users...manufacturers make
all kinds of coupler coupling values

And I meant that when a given coupling is desired, it is the physical
construction which gets you there.

...With 20 db coupling ...,
the main line is hardly affected whether the coupled line is terminated
in proper resistive value or open or shorted.

Sure. Weather or not you pull 1% of the power out, few of us will care.


name "directional."
This is a matter of primarily the mechanical design.
Mechanical AND electrical...that also influences the directivity.

Again, I was merely pointing out that good construction is necessary for
good directivity. In contrast to the "snaked" coax version which can have
highly variable performance.


The "directivity"
refers to the amount of power that gets coupled to the secondary line
that
emerges out the "wrong" end--not the one we want.

"Directivity" values are the sum of forward coupling and reverse
coupling. If a coupler has 20 db coupling and the directivity is
45 db, the reverse coupling is down 25 db. ...

I presume you intend to mean"...from the foward _coupled_ level." ???
This is what I was trying to say.

And don't forget conservation of energy. ...
At 20 db coupling, a bad coupled line termination results in a 1%



Probably going too far for the OP's original need I guess I'm just as
guilty of adding mounds of information that he OP might not be interestred
in.

They both should have a nice (50 ohm) impedance ...
Only if that is the main line characteristic impedance being used.
That's why I put the 50 in (), just as an example. I should have left
it out, but then I figured a question of "what is 'nice'" might have
surfaced.


...For the Moni-Match (snaked type) the secondary lines could be
some weird Zo and all is well if it is matched pretty well.
But...the amount of coupling CAN vary considerably with frequency
even though direction of coupling has an good relative agreement.

Sure. Again, I don't thing the OP is worried about flat freq response.
Many of us are familiar with the switched SWR meter with the pot to set the
FWD power to full scale and how that varies from band to band. We live with
it. At work, however, flat couplers are needed.
In fact, I was doing it last night. Was puzeled by the worse SWR on
teh lower bands of a high quality load. Could be... the SWR meter..
..

I'll base that on measuring the "snaked-through-the-large-coax" kind
(two different versions) intended for higher HF bands that had about
15 db difference between the two of them AND had quite a variation
in coupling over frequency.

Do you remember if you looked at the Zo of the coupled lines? I seem to
recall that in the articles, the termination of the coupled line is
considered an emperical optimization. cut-try for the value of load giving
"best" operation. I also wondered about the load seen at the end(s) where
the detectors were. Did they get a good match there. That;s going to mess
with your directivity, no? I guess you can put a good load on the main line
and just tweek for best directivity... a.k.a. lowest reading when line
matched - in BOTH directions. Seems that this is all you need to worry
about, for a ham, that is.


To make duplicates of an article's presentation requires a slavish
devotion to copying EXACTLY as described.

Again, that's where my comment about mechanigal construction came from.

By the way, you can pump power into the secondary line and have some come
out the mainline as well. This is actually done for special uses.
3 db couplers, also known as "hybrid couplers." Very good for making
wideband push-pull or push-push amplifiers out of modular amplifiers.

Won't go into detail, but high power linear amplifiers (60dB 2 tone IM)
in the 800MHz & 1800MHz range use 20 dB couplers for "Feed-Forward" IM
correction loops. Made an extensive "Backplane" with many stripline
couplers for them.


...High dielectric constant
in substrate allows making them smaller and the material insures
stability and good control in manufacture.
I have used Alumina. I also saw an article on microstrip couplers with
a complementary zig-zag pattern on the edges of the coupled lines adjacent
to each other...forget what the advantage was...I think increased coupling.


...Analog Devices log detector is
I saw that little bugger in QEX. Pretty cool!


73, Len

--
Steve N, K,9;d, c. i My email has no u's.

Take a look at:

http://www.ldgelectronics.com

It's a kit.

Regards

Ralf

--
Vy 73 es 55 de Ralf, DL2MRB
E-Mail:

Take a look at:

http://www.ldgelectronics.com

It's a kit.

Regards

Ralf

--
Vy 73 es 55 de Ralf, DL2MRB
E-Mail:

"Tom Bruhns" wrote in message
m...
"Steve Nosko" wrote in message
...

Side bar: I have one of the first directional power meters, the Micro
match. It uses a resistor, yes, resistor, for the current sense ...

Not really all that uncommon. A Wheatstone bridge works fine for
monitoring SWR...transformer-coupled versions...network analyzers...

[not trying to be or sound condecending (:-) I know all that. I was just
trying to help the OP understand this term "directional coupler" from the
ham perspective. In the context of today's *ham* SWR reading devices, having
a current sense resistor is unusual. Besides I am talking about a 1,000
watt full scale directional watt meter. It reads power directly in several
ranges. Supposedly what the modern ones do. So I was thinkin' a resistor
to sense current should be a bit of a surprise. In the 40's they didn't
have the transformers.
I also have a 5-1000 MHz SWR bridge, obviously low power as well. Spec'ed @
40 dB. Very lucky find. ain't cheap.

you are verrrry careful about the construction.
Yea, Yea. That's one of the points I was making.

You might think of microstrip or stripline as "hammered flat coax."

I'm ok with this analogy, I just had to add my 2 cents.

(And though stripline is true TEM, microstrip is quasi-TEM
I didn't think the OP cared about this. Also stripline is model-able,
micro strip (was only approximated) by Wheeler & Sobol, when I was designing
it. However, I think the OP wouldn't care about this either.


I believe a 1/4 wave is not important here.
Right...but beware of NULLS in the response at integer multiples of
1/2 wavelength,

I was thinking less than 1/4. I won't open it to see how long the
coupled lines are, but my Narda is about a foot long & goes down to .. gee,
I don't remember. Gotta go look tonight. I think 500M

They are pretty usefull things if you can get your hands on a good
one... and have the rest of the equipment to use it. I wasn't trying to
give the OP a tutorial on precision directional coupler design, just some
analogies to hang his hat on. Is the OP reading the rest this??

Typical directional coupler coupling is 20 db down from the main
line.
In fact, -20dB with 100 watts input gives you a WATT at the "FWD"
output,

That's why I didn't think it appropriate to say any particular value was
"standard". Get what you want. The physical construction determines the
coupling factor was where I was going as a contrast to the "snake-ed" ham
kind which has a variable construction and therefore coupling.


While not perfect, directional
coupling differences of about 20 db are good enough to warrant the
name "directional."
This is a matter of primarily the mechanical design.

AND the loading on the "other" end of the coupled line. Steve touched
on this,

Yea. I implied a lot with the "nice" comment (and invited much comment)
I see.

Enjoy your tools & Thanks guys, 73

--
Steve N, K,9;d, c. i My email has no u's.

"Tom Bruhns" wrote in message
m...
"Steve Nosko" wrote in message
...

Side bar: I have one of the first directional power meters, the Micro
match. It uses a resistor, yes, resistor, for the current sense ...

Not really all that uncommon. A Wheatstone bridge works fine for
monitoring SWR...transformer-coupled versions...network analyzers...

[not trying to be or sound condecending (:-) I know all that. I was just
trying to help the OP understand this term "directional coupler" from the
ham perspective. In the context of today's *ham* SWR reading devices, having
a current sense resistor is unusual. Besides I am talking about a 1,000
watt full scale directional watt meter. It reads power directly in several
ranges. Supposedly what the modern ones do. So I was thinkin' a resistor
to sense current should be a bit of a surprise. In the 40's they didn't
have the transformers.
I also have a 5-1000 MHz SWR bridge, obviously low power as well. Spec'ed @
40 dB. Very lucky find. ain't cheap.

you are verrrry careful about the construction.
Yea, Yea. That's one of the points I was making.

You might think of microstrip or stripline as "hammered flat coax."

I'm ok with this analogy, I just had to add my 2 cents.

(And though stripline is true TEM, microstrip is quasi-TEM
I didn't think the OP cared about this. Also stripline is model-able,
micro strip (was only approximated) by Wheeler & Sobol, when I was designing
it. However, I think the OP wouldn't care about this either.


I believe a 1/4 wave is not important here.
Right...but beware of NULLS in the response at integer multiples of
1/2 wavelength,

I was thinking less than 1/4. I won't open it to see how long the
coupled lines are, but my Narda is about a foot long & goes down to .. gee,
I don't remember. Gotta go look tonight. I think 500M

They are pretty usefull things if you can get your hands on a good
one... and have the rest of the equipment to use it. I wasn't trying to
give the OP a tutorial on precision directional coupler design, just some
analogies to hang his hat on. Is the OP reading the rest this??

Typical directional coupler coupling is 20 db down from the main
line.
In fact, -20dB with 100 watts input gives you a WATT at the "FWD"
output,

That's why I didn't think it appropriate to say any particular value was
"standard". Get what you want. The physical construction determines the
coupling factor was where I was going as a contrast to the "snake-ed" ham
kind which has a variable construction and therefore coupling.


While not perfect, directional
coupling differences of about 20 db are good enough to warrant the
name "directional."
This is a matter of primarily the mechanical design.

AND the loading on the "other" end of the coupled line. Steve touched
on this,

Yea. I implied a lot with the "nice" comment (and invited much comment)
I see.

Enjoy your tools & Thanks guys, 73

--
Steve N, K,9;d, c. i My email has no u's.

In article , "Steve Nosko"
writes:

WARNING
LONG WINDED POST BY TWO OLD FOGEYS...

Did I spell that correctly?

Heh. :-)


Then we get into deeper detail and possibly symmantics. I'll keep my
symmantics comments to a minimum since I was simply trying to provide a
simplified comparison with the monimatch and a little info on how they work.

Fine. :-)

I just added some things about directional couplers in general. These
postings are all very public and don't necessarily pertain to one
individual. Sometimes general information is an aid to a reader who
does not post. There's lots more readers than posters in most news-
groups.

Here's some links to couplers and power meters which are current
(checked today to see if they are still there):

http://www.ee.bilkent.edu.tr/~microwave/magnetic.htm

This site has HEAVY theory on - Rectangular waveguide, microstrip
antenna design and analysis, microwave filter design, Lange coupler
design, branch-line coupler design and analysis, directional coupler
design and analysis, 180 degree hybrid coupler design and analysis,
microwave power divider design and analysis. The "design and
analysis" includes an on-line calculator-applet to plug in numbers and
it grunges through the math for the user. It is practically a FREE book
on the basic UHF-microwave passive component region and should
save anyone's wallet to the tune of at least $120 (the old "Matthaei-
Young-Jones" hardcover is more than that now, even after 30+ years).

From the Microwaves & RF magazine archives, there is the February
2001 tutorial "Understanding The Basics Of Microstrip Directional
Couplers" by Leo Maloratsky, pp 79 to 94, a very concise article on a
large subject. Maloratsky worked for Rockwell Collins in Melbourne,
Florida at that time.

For direct SWR measurement using a Bruene detector and using meters
for readout of both forward and reverse power, the QEX article by Paul
Kiciak, N2PK, gives dimensional-construction information on the bridge
for HF and uses AD8307s as logarithmic detectors for both forward and
reverse plus op-amp couplers to the indicating meters. I have a PDF
that lacks the QEX identifying issue and page that was obtained from
another in July 2001, can't supply the QEX issue date or pages.

The Bruene bridge was first used in military T-195 transmitters that
became operational with USMC and US Army in 1955...part of a very
easy to use HF vehicular Tx/Rx using tubes and long vehicle whips.
Collins did the design under contract. A version of the Bruene
bridge is still used today in the US military in the AN/PRC-104
backpack 20 W HF radio which has an auto-tuner for the whip.
Hughes Aircraft designed, became operational in 1986.

I emphasize measurement methods because a finished coupler or
bridge or whatever needs to have something to measure it at lower
powers than available on Bird Wattmeters or similar. One of the
nicest applications of the Analog Devices AD8307 as a Wattmeter
with an 80 db dynamic range is on Thomas Schirrer's website:

http://www.webx.dk/oz2cpu/radios/milliwatt.htm

That one uses only two ICs, the AD8307 and a Microchip PIC16F876.
Accuracy of RF power measurement is all up to the AD8307 which
can work up past 500 MHz, has direct connections of RF input to the
AD8307. The PIC does conversion of AD8307 DC output volts to
either Watts or dbm and also controls the LCD panel unit (2 x 16
character integral LCD panel and driver). No other active devices are
needed except for the DC power supply. With appropriate programming,
serveral different PIC microcontrollers can be used. Several others have
copied the same circuit with variations on the case on display legend,
as indicated on the website. Simple and elegant. Calibrate once and
such will remain, error dependent solely on the AD8307.


...Analog Devices log detector is
I saw that little bugger in QEX. Pretty cool!

Lots of information on the Analog Devices website for datasheets and
application notes on their full line of logarithmic detectors. Why anyone
still wants to depend on germanium diode detectors with very limited
dynamic range and non-linear detection is beyond me. :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article , "Steve Nosko"
writes:

WARNING
LONG WINDED POST BY TWO OLD FOGEYS...

Did I spell that correctly?

Heh. :-)


Then we get into deeper detail and possibly symmantics. I'll keep my
symmantics comments to a minimum since I was simply trying to provide a
simplified comparison with the monimatch and a little info on how they work.

Fine. :-)

I just added some things about directional couplers in general. These
postings are all very public and don't necessarily pertain to one
individual. Sometimes general information is an aid to a reader who
does not post. There's lots more readers than posters in most news-
groups.

Here's some links to couplers and power meters which are current
(checked today to see if they are still there):

http://www.ee.bilkent.edu.tr/~microwave/magnetic.htm

This site has HEAVY theory on - Rectangular waveguide, microstrip
antenna design and analysis, microwave filter design, Lange coupler
design, branch-line coupler design and analysis, directional coupler
design and analysis, 180 degree hybrid coupler design and analysis,
microwave power divider design and analysis. The "design and
analysis" includes an on-line calculator-applet to plug in numbers and
it grunges through the math for the user. It is practically a FREE book
on the basic UHF-microwave passive component region and should
save anyone's wallet to the tune of at least $120 (the old "Matthaei-
Young-Jones" hardcover is more than that now, even after 30+ years).

From the Microwaves & RF magazine archives, there is the February
2001 tutorial "Understanding The Basics Of Microstrip Directional
Couplers" by Leo Maloratsky, pp 79 to 94, a very concise article on a
large subject. Maloratsky worked for Rockwell Collins in Melbourne,
Florida at that time.

For direct SWR measurement using a Bruene detector and using meters
for readout of both forward and reverse power, the QEX article by Paul
Kiciak, N2PK, gives dimensional-construction information on the bridge
for HF and uses AD8307s as logarithmic detectors for both forward and
reverse plus op-amp couplers to the indicating meters. I have a PDF
that lacks the QEX identifying issue and page that was obtained from
another in July 2001, can't supply the QEX issue date or pages.

The Bruene bridge was first used in military T-195 transmitters that
became operational with USMC and US Army in 1955...part of a very
easy to use HF vehicular Tx/Rx using tubes and long vehicle whips.
Collins did the design under contract. A version of the Bruene
bridge is still used today in the US military in the AN/PRC-104
backpack 20 W HF radio which has an auto-tuner for the whip.
Hughes Aircraft designed, became operational in 1986.

I emphasize measurement methods because a finished coupler or
bridge or whatever needs to have something to measure it at lower
powers than available on Bird Wattmeters or similar. One of the
nicest applications of the Analog Devices AD8307 as a Wattmeter
with an 80 db dynamic range is on Thomas Schirrer's website:

http://www.webx.dk/oz2cpu/radios/milliwatt.htm

That one uses only two ICs, the AD8307 and a Microchip PIC16F876.
Accuracy of RF power measurement is all up to the AD8307 which
can work up past 500 MHz, has direct connections of RF input to the
AD8307. The PIC does conversion of AD8307 DC output volts to
either Watts or dbm and also controls the LCD panel unit (2 x 16
character integral LCD panel and driver). No other active devices are
needed except for the DC power supply. With appropriate programming,
serveral different PIC microcontrollers can be used. Several others have
copied the same circuit with variations on the case on display legend,
as indicated on the website. Simple and elegant. Calibrate once and
such will remain, error dependent solely on the AD8307.


...Analog Devices log detector is
I saw that little bugger in QEX. Pretty cool!

Lots of information on the Analog Devices website for datasheets and
application notes on their full line of logarithmic detectors. Why anyone
still wants to depend on germanium diode detectors with very limited
dynamic range and non-linear detection is beyond me. :-)

Len Anderson
retired (from regular hours) electronic engineer person

I didn't think of it, but what a great application for that bugger!

--
Steve N, K,9;d, c. i My email has no u's.

"Avery Fineman" wrote in message
...
In article , "Steve Nosko"
writes:


...Analog Devices log detector is
I saw that little bugger in QEX. Pretty cool!

Lots of information on the Analog Devices website for datasheets and
application notes on their full line of logarithmic detectors. Why
anyone
still wants to depend on germanium diode detectors with very limited
dynamic range and non-linear detection is beyond me. :-)

Len Anderson
retired (from regular hours) electronic engineer person