On Sat, 21 Feb 2009 19:37:34 -0600, Frnak McKenney
wrote:

Matching provokes heated debates that in times past ran to 600+
postings - few knew what they were arguing (but enjoyed arguing
nonetheless) and little was offered.

What I think I'm looking for would be a point of reference that
would let me, if not exactly evaluate the facets of such an
argument, at least be a foundation for forming a testable opinion of
my own.

Opinion is, after all, what powers the Internet.

A JFET at these frequencies does satisfy the naive requirements of
"matching," but that giving you a reception solution doesn't always
follow.

In my current state of ignorance of the subject, this sentence has
the appearance of a Zen koan: something that sounds non-sensical at
first glance, but which, after sufficient time and effort studying,
will undoubtedly become so blindingly obvious as to appear trivial.
Thank you... I think. grin!

I could reduce it to the classic "take two aspirin and call me in the
morning."

Ah! You have a Mohican? Or just access to the manual? Mine is missing,
burioed somewhere in my basement; I was fortunate enough to locate a
copy of a GC-1A PDF some kind soul posted online.

It didn't take much effort to scour the web for one (schematic).

You don't need wire to build an inductor. At these frequencies you
can use a capacitor in a Gyrator design.

"Gyrator"? I thought that was the rooftop dance that follows an
antenna adjustment in mid-thunderstorm. grin!

Google led me to the AAVSO site (www.aavso.org) which led me to the
Yahoo VLF_Group. Aaaaaaaaaaaaaaauuuuuuuggggh! A circuit that can
replace capacitors or inductors? My first reaction is "technology
at a level indistunguisable from black magic".

I don't think I'm in Kansas any more.

Gyrators have been around for a very long time, and can be found in a
billion telephones, one probably within reach of you at the moment.
They use telephones in Kansas don't they, Toto? You can build one
with four components (none of them an inductor) to make an inductor
more precisely than you could winding one.

If you truly want to be overwhelmed with the dark arts, try googling
for "magnetic amplifiers." (Art would go ballistic knowing such a
topic was in practice looooong before he left second form.) No tubes,
no transistors, and the orginal "solid state" design. As this may
sound as if it wanders from the subject of RF, add the name Ernst F.
W. Alexanderson to any search.

(On the other hand, I have lots more toys to play with. grin!)

all of the surrounding
EM sets the electroncs in the wire to dancing, but the series RC
blocks those which are wiggling "off-key" (e.g. not dancing at the
"proper" rate of 60kHz).

And this responds to the filtering capacity (selection AND
rejection). This is called "Q" which also serves the yeoman's
task of matching as well

Um. I don't think I ever got past the simplistic "High Q = Good,
Low Q = Evil" stage. Looking back, I can now see cases where an
excessively high Q might be... counterproductive, but as always, it
depends on what one means by "high" or "low" in a given context.

Noted as something else I need to review and not depend on instinct
for.

... (observe the input tank design for the
conventional bands).

Of the five bands (A-E, SW3 positions 5-1), the only one which seems
different is "E", with an additional 130pF cap between the antenna
and the tank circuit.

Is that what you're referring to?

I am merely pointing out the obvious application of a tapped inductor
of the tuned front end serving as impedance match to an high-Z antenna
(the topic of your choice). The schematic abounds in examples. One
need only substitute values to serve the right frequency band - a
simple exercise in reverse engineering employed since Hertz drew a
spark across a gap at the base of a loop.

If you're getting bored, please feel free to skip the following; on
the other hand, someone with access to a GC-1 manual might enjoy my
story...

Yes, your story was/is classic with a beginning, middle, and end. Very
few chroniclers here manage to write with as much clarity. (We get
mostly cheesy attempts with "cliff hangers" serving as examples of
neo-scholarly writing.) Your learning lesson of maintaining the
chassis ground with the trace is classic too. The discovery of
corrosion brings up the common practice of taking ALL the tubes out
and putting them back in to solve problems. Tightening ALL screws is
another hard learned lesson that bench techs either get or don't get.

You probably could have got away with cheaper transistors by also
substituting the bias diodes (56-7s) - but as events bore out, the
transistors were good. If you note the difference between the base
and emitter voltages, there is only about a tenth volt there. If I am
to presume the diode call-out is for an 1N56, it is germanium too.

What is more amazing is this wasn't about the decrepitude of the
electrolytic capacitors which usually suffer with time if they are not
used for a long while.

73's
Richard Clark, KB7QHC

Jimmie,

Thank you for your comments.

On Wed, 18 Feb 2009 13:19:12 -0800 (PST), JIMMIE wrote:
On Feb 18, 3:12*pm, Richard Clark wrote:
On Wed, 18 Feb 2009 12:06:09 -0600, Frnak McKenney

wrote:
What has puzzled me is that I have run across designs that use
(e.g.) a JFET isolation amplifier hooked to a whip or hunk-o-wire
with the statement (or implication) that this is done to ",atch the
antenna's impedance".

Hi Frank,

Matching provokes heated debates that in times past ran to 600+
postings - few knew what they were arguing (but enjoyed arguing
nonetheless) and little was offered.

A JFET at these frequencies does satisfy the naive requirements of
"matching," but that giving you a reception solution doesn't always
follow.
--snip--
Its not uncommon to have a high impedance input into a preamp.
This is the one-size- fits-all approach. While its not good
engineering for the purist it works quite well to make a casual user
happy and may be the practical solution for even the professional
installation..

Well, I think of myself as a "casual user", and _I'd_ like to be
happy. grin!

I don't mind throwing in a high-impedance (JFET) front end to my
antenna simply on the basis that (a) people who seem to know what
they're talking about recommend it and (b) I associate "high
impedance" with "sensitive" (which seems like a desirable quality
when you're working with microvolts). Someday, though, I'd like to
have build up a framework in which _I_ can see why it's appropriate,
or at least "does no harm". grin!

My brother Bruce is working on the same problem from a slightly
different angle; his experience is in software and digital stuff,
and I find myself unintentionally assuming the role of "RF expert"
without an EE degree or years of circuit design to back it up. Left
to myself, I'm perfectly capable of pushing stuff around on the
breadboard until it seems to work, but when I'm offering advice to
someone else I'd prefer a better response to his questions than
"someone else said so". grin!

Ive had some experience limited working with VLF and it always
seemed the thing that made the difference between a good and bad VLF
antenna was the quality of the ground network

Thanks for the suggestion. Do you think that my current "ground", a
30x60' 4-way pipe-loop network (mixed copper and cast iron) with
thermal radiation elements might be... um, "less than
satisfactory"? grin!


Frank
--
"What one writer can make in the solitude of one room is something
no power can easily destroy." -- Salman Rushdie
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)

Mark,

Thank you for joining in.

On Wed, 18 Feb 2009 20:57:00 GMT, Mark Zenier wrote:
In article ,
Frnak McKenney wrote:

Big Snip.

And much appreciated by me and others. grin!

Go find Radio-Electronics magazine for 1983, and read the five(?)
articles by Ralph Burhans about receiving VLF.

I ran across one article he wrote, in PDF format, but couldn't
locate the articles. Have you seen them posted anywhere?

Also, Dr. Barry Ornitz was kind enough to send me a PDF file
describing two books available from the ARRL online store at
http://www.arrl.org/:

Mike Dennison and Jim Moritz: LF Today
Peter Dodd: The Low Frequency Expermenter's Handbook

He also took the time to offer a description of why a JFET input
matches a high impedance. The words seem to fit together, but I'm
still working on downconverting it to a frequency low enough for my
brain to accept. grin!


Frank
--
ÿPeople demand freedom of speech to make up for the freedom of
thought which they avoid.ÿ -- Soren Kierkegaard
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)

On Feb 22, 11:57*am, Frnak McKenney
wrote:
Mark,

Thank you for joining in.

On Wed, 18 Feb 2009 20:57:00 GMT, Mark Zenier wrote:
In article ,
Frnak McKenney wrote:

Big Snip.

And much appreciated by me and others. grin!

Go find Radio-Electronics magazine for 1983, and read the five(?)
articles by Ralph Burhans about receiving VLF.

I ran across one article he wrote, in PDF format, but couldn't
locate the articles. Have you seen them posted anywhere?

Also, Dr. *Barry Ornitz was kind enough to send me a PDF file
describing two books available from the ARRL online store athttp://www.arrl.org/:

* Mike Dennison and Jim Moritz: LF Today
* Peter Dodd: The Low Frequency Expermenter's Handbook

He also took the time to offer a description of why a JFET input
matches a high impedance. *The words seem to fit together, but I'm
still working on downconverting it to a frequency low enough for my
brain to accept. *grin!

Frank
--
* ÿPeople demand freedom of speech to make up for the freedom of
* *thought which they avoid.ÿ -- Soren Kierkegaard
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)

The first time I tried to dabble with VLF the rx front end I found
from an university paper was nothing more than a triode(probably 1/2 a
12AX7) amp using a couple of TV horizontal osc coils as the tank
circuit. After breadboarding the rx up on an old TV chassis I kept it
around for a few years soon loosing interest in the CW and man made
data transmisssions. There seem to be quite a few naturally occuring
sources of RF in that band that sound interesting, some almost
musical.

Jimmie

On Sat, 21 Feb 2009 22:13:47 -0800, Richard Clark wrote:
On Sat, 21 Feb 2009 19:37:34 -0600, Frnak McKenney
wrote:
--snip--
Google led me to the AAVSO site (www.aavso.org) which led me to the
Yahoo VLF_Group. Aaaaaaaaaaaaaaauuuuuuuggggh! A circuit that can
replace capacitors or inductors? My first reaction is "technology
at a level indistunguisable from black magic".

I don't think I'm in Kansas any more.

Gyrators have been around for a very long time, and can be found in a
billion telephones, one probably within reach of you at the moment.
They use telephones in Kansas don't they, Toto? You can build one
with four components (none of them an inductor) to make an inductor

That's what the man said... I saw the schematics for Gyrators I-III,
and I need to go back and re-read the decriptive text.

more precisely than you could winding one.

That doesn't take much. I've had days recently where I felt like I
could wind a mile of wire around a ferrite rod and _still_ not make
an inductor. grin!

If you truly want to be overwhelmed with the dark arts, try googling
for "magnetic amplifiers." (Art would go ballistic knowing such a
topic was in practice looooong before he left second form.) No tubes,
no transistors, and the orginal "solid state" design. As this may
sound as if it wanders from the subject of RF, add the name Ernst F.
W. Alexanderson to any search.

Noted and filed, but I think I'm beginning to be "overwhelmed by
insurmountable opportunities". grin!

--snip--
( the Mohican antenna circuitry)
Of the five bands (A-E, SW3 positions 5-1), the only one which seems
different is "E", with an additional 130pF cap between the antenna
and the tank circuit.

Is that what you're referring to?

I am merely pointing out the obvious application of a tapped
inductor of the tuned front end serving as impedance match to an
high-Z antenna (the topic of your choice).

Oh. Okay. "Parallel LC (tank) circuit = high impedance. Coil tapped
to match lower impedance". Gotcha. I got lost trying to figure out
your reference to "conventional bands".

... The schematic abounds in examples.

Yup. You don't see many AM/FM radios these days with three tank
circuits per band. grin!

... One
need only substitute values to serve the right frequency band - a
simple exercise in reverse engineering employed since Hertz drew a
spark across a gap at the base of a loop.

Which was, in its own time, pretty close to "magic".

I've been trying to stir some excitement in the one niece and nephew
who are talking of studying engineering next year, but it's tough.
They seem to be so constantly surrounded by wonders that they take
them for granted.

--snip--
... Your learning lesson of maintaining the
chassis ground with the trace is classic too. The discovery of
corrosion brings up the common practice of taking ALL the tubes out
and putting them back in to solve problems.

It's still surprising to me just how often taking something apart
and putting it together again will get it working again. Doesn't
even require mystical passes with my hands (but I occasionally add
them anyway grin!).

... Tightening ALL screws is
another hard learned lesson that bench techs either get or don't get.

Finished with the Mohican this afternoon. I wound up taking out the
eleven machine screws around the IF/audio PC board out (they were
all still tight, FYI). I then ran some fine steel wool around in
the gap and reassembled it; turned out that I had to unbolt the
audio transformer and 1/4" earphone jack to get the lockwashers and
nuts back on four of them. When I finished there was no leftover
hardware, a small miracle in itself.

It still doesn't buzz. (Yayyyyy!)

You probably could have got away with cheaper transistors by also
substituting the bias diodes (56-7s) - but as events bore out, the
transistors were good. If you note the difference between the base
and emitter voltages, there is only about a tenth volt there. If I am
to presume the diode call-out is for an 1N56, it is germanium too.

Oh. A 56-7 is a 1N56? I wasn't sure about substituting them, and
finding any Germanium parts on this side of the Pond is tough.

I was about ready to bypass the entire audio section and wire in a
small LM386-or-similar amplifier in its place. Might still do it
next time.

What is more amazing is this wasn't about the decrepitude of the
electrolytic capacitors which usually suffer with time if they are not
used for a long while.

When I first heard the buzz, my first instinct was to check the
electrolytics. I even tried parallelling the X7 emitter bypass, but
because _that_ time I did it by hooking my jumpers to the component
leads on top of the PC board, the effort had no effect. Ack! Phlbbbbt!
So _close_...

I have to say that those Gyrator circuits are really appealing. I
may throw one togehter just to see what happens. Thanks for
pointing me at them. (Now if someone would just design a "network
component" that replaced _intelligence_ with four components, none
of them involving intelligence... grin!)

Thanks again for your feedback.


Frank
--
Fashion is...a search for a new language to discredit the old,
a way in which each generation can repudiate its immediate
predecessor and distinguish itself from it.
-- Fernand Braudel/Civilization & Capitalism, 15th-18th Century
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)

On Feb 17, 11:05*pm, "Sal M. Onella"
wrote:
"Phil Allison" wrote in message

...



"Frnak McKenney"
*http://ts.nist.gov/MeasurementServic...d/SP250-67.pdf
** Just how big is this file * * - *eh *??
Why did you limit replies to *ONE *newsgroup while posting *to TWO * ???
What sort to total *****ING *ASSHOLE *are you * ????
You ****ing *ASININE *YANK *****- head.
..... * Phil

Uh-oh! *Looks like somebody isn't getting enough fiber!

I think he just has "Little P***** Syndrome".
So Sorry Phil for the little D***!!!! HI HI

Joe

Frnak McKenney wrote:

In my current state of ignorance of the subject, this sentence has
the appearance of a Zen koan: something that sounds non-sensical at
first glance, but which, after sufficient time and effort studying,
will undoubtedly become so blindingly obvious as to appear trivial.
Thank you... I think. grin!


As witnessed by the great Zen master, Yogi Berra......


Sorry, catching up on the groups and couldn't resist.

- 73 de Mike N3LI -

On Feb 22, 9:19*pm, Frnak McKenney
wrote:
On Sat, 21 Feb 2009 22:13:47 -0800, Richard Clark wrote:
On Sat, 21 Feb 2009 19:37:34 -0600, Frnak McKenney
wrote:
--snip--
Google led me to the AAVSO site (www.aavso.org) which led me to the
Yahoo VLF_Group. *Aaaaaaaaaaaaaaauuuuuuuggggh! *A circuit that can
replace capacitors or inductors? *My first reaction is "technology
at a level indistunguisable from black magic".

I don't think I'm in Kansas any more.

Gyrators have been around for a very long time, and can be found in a
billion telephones, one probably within reach of you at the moment.
They use telephones in Kansas don't they, Toto? *You can build one
with four components (none of them an inductor) to make an inductor

That's what the man said... I saw the schematics for Gyrators I-III,
and I need to go back and re-read the decriptive text.

more precisely than you could winding one.

That doesn't take much. *I've had days recently where I felt like I
could wind a mile of wire around a ferrite rod and _still_ not make
an inductor. grin!

If you truly want to be overwhelmed with the dark arts, try googling
for "magnetic amplifiers." (Art would go ballistic knowing such a
topic was in practice looooong before he left second form.) *No tubes,
no transistors, and the orginal "solid state" design. *As this may
sound as if it wanders from the subject of RF, add the name Ernst F.
W. Alexanderson to any search.

Noted and filed, but I think I'm beginning to be "overwhelmed by
insurmountable opportunities". *grin!

--snip--
( the Mohican antenna circuitry)

Of the five bands (A-E, SW3 positions 5-1), the only one which seems
different is "E", with an additional 130pF cap between the antenna
and the tank circuit.

Is that what you're referring to?

I am merely pointing out the obvious application of a tapped
inductor of the tuned front end serving as impedance match to an
high-Z antenna (the topic of your choice).

Oh. Okay. "Parallel LC (tank) circuit = high impedance. Coil tapped
to match lower impedance". Gotcha. I got lost trying to figure out
your reference to "conventional bands".

... *The schematic abounds in examples.

Yup. You don't see many AM/FM radios these days with three tank
circuits per band. grin!

... *One
need only substitute values to serve the right frequency band - a
simple exercise in reverse engineering employed since Hertz drew a
spark across a gap at the base of a loop.

Which was, in its own time, pretty close to "magic".

I've been trying to stir some excitement in the one niece and nephew
who are talking of studying engineering next year, but it's tough.
They seem to be so constantly surrounded by wonders that they take
them for granted.

--snip--

... *Your learning lesson of maintaining the
chassis ground with the trace is classic too. *The discovery of
corrosion brings up the common practice of taking ALL the tubes out
and putting them back in to solve problems.

It's still surprising to me just how often taking something apart
and putting it together again will get it working again. *Doesn't
even require mystical passes with my hands (but I occasionally add
them anyway grin!).

... *Tightening ALL screws is
another hard learned lesson that bench techs either get or don't get.

Finished with the Mohican this afternoon. *I wound up taking out the
eleven machine screws around the IF/audio PC board out (they were
all still tight, FYI). *I then ran some fine steel wool around in
the gap and reassembled it; turned out that I had to unbolt the
audio transformer and 1/4" earphone jack to get the lockwashers and
nuts back on four of them. *When I finished there was no leftover
hardware, a small miracle in itself.

It still doesn't buzz. (Yayyyyy!)

You probably could have got away with cheaper transistors by also
substituting the bias diodes (56-7s) - but as events bore out, the
transistors were good. *If you note the difference between the base
and emitter voltages, there is only about a tenth volt there. *If I am
to presume the diode call-out is for an 1N56, it is germanium too.

Oh. *A 56-7 is a 1N56? *I wasn't sure about substituting them, and
finding any Germanium parts on this side of the Pond is tough.

I was about ready to bypass the entire audio section and wire in a
small LM386-or-similar amplifier in its place. *Might still do it
next time.

What is more amazing is this wasn't about the decrepitude of the
electrolytic capacitors which usually suffer with time if they are not
used for a long while.

When I first heard the buzz, my first instinct was to check the
electrolytics. *I even tried parallelling the X7 emitter bypass, but
because _that_ time I did it by hooking my jumpers to the component
leads on top of the PC board, the effort had no effect. Ack! Phlbbbbt!
So _close_...

I have to say that those Gyrator circuits are really appealing. *I
may throw one togehter just to see what happens. *Thanks for
pointing me at them. *(Now if someone would just design a "network
component" that replaced _intelligence_ with four components, none
of them involving intelligence... *grin!)

Thanks again for your feedback.

Frank
--
* * Fashion is...a search for a new language to discredit the old,
* * a way in which each generation can repudiate its immediate
* * predecessor and distinguish itself from it.
* * -- Fernand Braudel/Civilization & Capitalism, 15th-18th Century
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)

One of the most common places gyrators are used today is in graphic
equalizers. I wonder if a graphic equalizer could be built to cover
the VLF band complete with LED bargraph(grim). The first graphic eq I
ever saw had tons of coils in it and vaccums tubes and must have cost
a few $K. The second one I saw was made with ICs no coils and cost
about $500. It was replacing the first one I saw.

JImmie