Curious about the I.R.E. Standard Dummy Antenna
 

I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

I first came across this circuit in some old Hallicrafter's
documentation, which described the alignment of a particular radio. The
"IRE Standard Dummy Antenna" consists of four components--- a 200pf cap
in series with a 20 uH inductor, which links the signal generator to the
receiver's antenna input. A 400 pF cap in series with a 400 ohm resistor
is connected in parallel with (shunts)the inductor.

I gather that this circuit models a wire antenna of some type. Is this
true? What is the import of the component values and how were they
arrived at? I modeled the circuit in Spice and graphed the transfer and
impedance curves but it is not entirely clear to me what benefit there
is to using this circuit.

I've also Googled this and found some references here and there, but
nothing explains the "why" of it.

Is there anyone who can shed light on this?

73
Pete
AC7ZL

hpf (at) gainbroadband (dot) com

Curious about the I.R.E. Standard Dummy Antenna
 

"H. P. Friedrichs" wrote:

I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

I first came across this circuit in some old Hallicrafter's
documentation, which described the alignment of a particular radio. The
"IRE Standard Dummy Antenna" consists of four components--- a 200pf cap
in series with a 20 uH inductor, which links the signal generator to the
receiver's antenna input. A 400 pF cap in series with a 400 ohm resistor
is connected in parallel with (shunts)the inductor.

I gather that this circuit models a wire antenna of some type. Is this
true? What is the import of the component values and how were they
arrived at? I modeled the circuit in Spice and graphed the transfer and
impedance curves but it is not entirely clear to me what benefit there
is to using this circuit.

I've also Googled this and found some references here and there, but
nothing explains the "why" of it.

Is there anyone who can shed light on this?

73
Pete
AC7ZL

hpf (at) gainbroadband (dot) com


Its to match the receiver to the generator.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Curious about the I.R.E. Standard Dummy Antenna
 

Michael A. Terrell wrote:
"H. P. Friedrichs" wrote:

I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

Its to match the receiver to the generator.

Or more specifically, it's to present a uniform high impedance
from the generator to the radio. At the time, with the exception
of a few lab grade instruments, signal generator outputs were all
over the map with regards to output impedance. The "dummy antenna"
presented a fairly uniform, and high, impedance to the radio and
kept from detuning the front end while doing an alignment while
connected to a signal generator.

Jeff


--
RESTRICTED AREA. Anyone intruding shall immediately become subject to
the jurisdiction of military law. Intruders will be subject to lethal
force, without warning, and on sight. USE OF DEADLY FORCE IS AUTHORIZED
under the Internal Security Act of 1950.

Curious about the I.R.E. Standard Dummy Antenna
 

"Jeffrey D Angus" wrote in message
...

Or more specifically, it's to present a uniform high impedance
from the generator to the radio. At the time, with the exception
of a few lab grade instruments, signal generator outputs were all
over the map with regards to output impedance. The "dummy antenna"
presented a fairly uniform, and high, impedance to the radio and
kept from detuning the front end while doing an alignment while
connected to a signal generator.

Jeff


Ahhh, so for the very first time, I finally hear an answer to one of those
things that I've scratched my head about for years!

I've often wondered why the literature always says to stick a capacitor
inline from the signal generator -- I figured if I had to do this all the
time, then why didn't the signal generator maker put one in there? Turns
out, usually they do, but it's probably not an impedance match. Still, for
most radios I just stick the probe to the antenna and go to town. It's fine
for the IF -- enough of it gets past the RF to give me a workable signal.
Then for RF I use whatever frequency I need to check/adjust the LO. For
final RF adjustments I plug in the antenna and tweak it up on a weak
station.

Again, I probably differ from most of you because I work mainly with car
radios. I already have a pretty decent antenna at the bench -- some $10
special from Auto Zone -- that does a great job. On a conversion there are
no RF adjustments; on a repair/rebuild, I can do every adjustment except
one, the one which must be done inside the car anyway -- the antenna
trimmer. However even this gets checked -- I've noticed that with my bench
antenna, the trimmer usually adjusts toward the "high" end, with the screw
fairly loose. So if the trimmer tweaks in this area I'm fine. If it tweaks
"tight", or not at all, I'll adjust the slug as needed -- or troubleshoot.

Actually it is rare that I ever have such a problem -- with one exception:
the 58-60 T-Bird radios. Even these are just fine, usually, but I've had a
number of them whose front ends are way off. I've spent many hours trying
to figure out why, and come up with nothing. I've replaced RF caps, checked
the range of trimmers, checked resistor tolerances, and basically gone over
the circuit with a fine tooth comb. Everything checks perfect, but the
alignment is out. So I adjust the tuning slug -- a pretty fair distance --
to bring it in line. I've had a couple that were so far off that I had to
tinker with the others as well. It's really fun because those slugs are
WAA-AAY up in there, and difficult to reach. You can't do it with a
non-ferocious screwdriver, or even a ferocious one -- it's too tight. You
have to reach the shaft with needle-nose. In any case, all this fun aside,
I can tinker and bring it into line -- but I still wonder why I have to do
it in the first place.

I think my next step in this "investigation" is to spend time with the next
58-60 T-Bird I get for conversion. If it's a good radio, when I disassemble
I'll measure the tuning slugs, trimmers, fixed coils, etc., and write them
down for reference.

--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

Curious about the I.R.E. Standard Dummy Antenna
 

Maybe the slugs have lost some permeability. Which way do you have to
tune, more or less inductance? Ken

Gary Tayman wrote:

"Jeffrey D Angus" wrote in message
...

Or more specifically, it's to present a uniform high impedance
from the generator to the radio. At the time, with the exception
of a few lab grade instruments, signal generator outputs were all
over the map with regards to output impedance. The "dummy antenna"
presented a fairly uniform, and high, impedance to the radio and
kept from detuning the front end while doing an alignment while
connected to a signal generator.

Jeff



Ahhh, so for the very first time, I finally hear an answer to one of those
things that I've scratched my head about for years!

I've often wondered why the literature always says to stick a capacitor
inline from the signal generator -- I figured if I had to do this all the
time, then why didn't the signal generator maker put one in there? Turns
out, usually they do, but it's probably not an impedance match. Still, for
most radios I just stick the probe to the antenna and go to town. It's fine
for the IF -- enough of it gets past the RF to give me a workable signal.
Then for RF I use whatever frequency I need to check/adjust the LO. For
final RF adjustments I plug in the antenna and tweak it up on a weak
station.

Again, I probably differ from most of you because I work mainly with car
radios. I already have a pretty decent antenna at the bench -- some $10
special from Auto Zone -- that does a great job. On a conversion there are
no RF adjustments; on a repair/rebuild, I can do every adjustment except
one, the one which must be done inside the car anyway -- the antenna
trimmer. However even this gets checked -- I've noticed that with my bench
antenna, the trimmer usually adjusts toward the "high" end, with the screw
fairly loose. So if the trimmer tweaks in this area I'm fine. If it tweaks
"tight", or not at all, I'll adjust the slug as needed -- or troubleshoot.

Actually it is rare that I ever have such a problem -- with one exception:
the 58-60 T-Bird radios. Even these are just fine, usually, but I've had a
number of them whose front ends are way off. I've spent many hours trying
to figure out why, and come up with nothing. I've replaced RF caps, checked
the range of trimmers, checked resistor tolerances, and basically gone over
the circuit with a fine tooth comb. Everything checks perfect, but the
alignment is out. So I adjust the tuning slug -- a pretty fair distance --
to bring it in line. I've had a couple that were so far off that I had to
tinker with the others as well. It's really fun because those slugs are
WAA-AAY up in there, and difficult to reach. You can't do it with a
non-ferocious screwdriver, or even a ferocious one -- it's too tight. You
have to reach the shaft with needle-nose. In any case, all this fun aside,
I can tinker and bring it into line -- but I still wonder why I have to do
it in the first place.

I think my next step in this "investigation" is to spend time with the next
58-60 T-Bird I get for conversion. If it's a good radio, when I disassemble
I'll measure the tuning slugs, trimmers, fixed coils, etc., and write them
down for reference.

Curious about the I.R.E. Standard Dummy Antenna
 

"H. P. Friedrichs" wrote in message
news:1YOdna1FqcOin2DZnZ2dnUVZ_tCdnZ2d@velocitywest .com...
I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

I first came across this circuit in some old Hallicrafter's
documentation, which described the alignment of a particular radio. The
"IRE Standard Dummy Antenna" consists of four components--- a 200pf cap
in series with a 20 uH inductor, which links the signal generator to the
receiver's antenna input. A 400 pF cap in series with a 400 ohm resistor
is connected in parallel with (shunts)the inductor.

I gather that this circuit models a wire antenna of some type. Is this
true? What is the import of the component values and how were they
arrived at? I modeled the circuit in Spice and graphed the transfer and
impedance curves but it is not entirely clear to me what benefit there
is to using this circuit.

I've also Googled this and found some references here and there, but
nothing explains the "why" of it.

Is there anyone who can shed light on this?

73
Pete
AC7ZL

Yes, the dummy antenna models a wire resonant at 2.something Mc. I suppose
that was taken to be more or less typical of the receiver antennas of the
30s. The dummy antenna's most important use is as a standardized load for
measuring receiver sensitivity. Terman's Radio Engineer's Handbook has a
few paragraphs on this.

If you're just adjusting the RF coils, peaking them up on the antenna
normally used would be as good or better. Any sort of loose coupling
between the generator and RF coils will get you in the ballpark with most
radios.

Frank Dresser

Curious about the I.R.E. Standard Dummy Antenna
 

In article ,
wrote:

Michael A. Terrell wrote:
"H. P. Friedrichs" wrote:

I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

Its to match the receiver to the generator.

Or more specifically, it's to present a uniform high impedance
from the generator to the radio. At the time, with the exception
of a few lab grade instruments, signal generator outputs were all
over the map with regards to output impedance. The "dummy antenna"
presented a fairly uniform, and high, impedance to the radio and
kept from detuning the front end while doing an alignment while
connected to a signal generator.
This doesn't sound right, why would it be desirable "to present a uniform
high impedance from the generator to the radio"? The impedance of the
"IRE Standard Dummy Antenna" is not exactly what I would call "high"
especially on some of the short wave bands, exactly what is a high
impedance in this context?

It was my understanding that the purpose of the "IRE Standard Dummy
Antenna" was to provide a standard antenna to use for making performance
measurements, as well as for alignment at the factory and on the service
bench.

As to the exact design of the of the "IRE Standard Dummy Antenna", I
understood that it was meant to represent the impedance characteristics a
typical antenna that might be used by a radio set owner. This topic has
been discussed here before and I seem to vaguely remember that someone may
have even dug up the exact nature of the antenna the "IRE Standard Dummy
Antenna" was designed to simulate. IIRC if you are only doing MW
broadcast band alignments a single capacitor will provide a very good
approximation of the "IRE Standard Dummy Antenna" across the MW broadcast
band. The coil, resistor and second capacitor are there mainly to provide
the desired impedance on the short wave bands where the prototype antenna
has resonant effects

There are at least two problems that the "IRE Standard Dummy Antenna"
solves, the first being standardized measurements for obtaining
performance specifications, as it is possible for a manufacturer to
"improve" his products specifications by using his own specially designed
"Dummy Antenna". The second problem is how to align sets in the factory,
or on the service bench, when the final users actual antenna system is not
available. The problem is that the alignment of the antenna stage of a
radio is greatly affected by the impedance of the actual antenna that is
used with the radio. The "IRE Standard Dummy Antenna" provides an
approximation of what was assumed to be a typical consumer antenna. Of
course what you really want to do is align the set with the actual antenna
attached that it is used with.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

Curious about the I.R.E. Standard Dummy Antenna
 

Well put, John.
I have understood the purpose of the 'matching network' for years, but
I have been puzzled by the source impedance expected on the generator
side.
I have several RF generators of various vintages in my collection and
most of the older tube ones have most peculiar output attenuators that
would have impedances that vary all over the place depending on the
setting of the output attenuator, frequency and, to some degree, output
cable length. On 'modern' generators, once you cut in 10dB or more of
attenuator, the output inpedance it pretty close to the specified, but
even many of them are quite a low impedance at 0 dB.
Perhaps someone with spice can characterize the output impedance of the
IRE network when fed from a generator of 0 ohm, 50 ohm, 75 ohm and,
say, 200 ohm output impedance.

Neil S.

John Byrns wrote:
In article ,
wrote:

Michael A. Terrell wrote:
"H. P. Friedrichs" wrote:

I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

Its to match the receiver to the generator.

Or more specifically, it's to present a uniform high impedance
from the generator to the radio. At the time, with the exception
of a few lab grade instruments, signal generator outputs were all
over the map with regards to output impedance. The "dummy antenna"
presented a fairly uniform, and high, impedance to the radio and
kept from detuning the front end while doing an alignment while
connected to a signal generator.
This doesn't sound right, why would it be desirable "to present a uniform
high impedance from the generator to the radio"? The impedance of the
"IRE Standard Dummy Antenna" is not exactly what I would call "high"
especially on some of the short wave bands, exactly what is a high
impedance in this context?

It was my understanding that the purpose of the "IRE Standard Dummy
Antenna" was to provide a standard antenna to use for making performance
measurements, as well as for alignment at the factory and on the service
bench.

As to the exact design of the of the "IRE Standard Dummy Antenna", I
understood that it was meant to represent the impedance characteristics a
typical antenna that might be used by a radio set owner. This topic has
been discussed here before and I seem to vaguely remember that someone may
have even dug up the exact nature of the antenna the "IRE Standard Dummy
Antenna" was designed to simulate. IIRC if you are only doing MW
broadcast band alignments a single capacitor will provide a very good
approximation of the "IRE Standard Dummy Antenna" across the MW broadcast
band. The coil, resistor and second capacitor are there mainly to provide
the desired impedance on the short wave bands where the prototype antenna
has resonant effects

There are at least two problems that the "IRE Standard Dummy Antenna"
solves, the first being standardized measurements for obtaining
performance specifications, as it is possible for a manufacturer to
"improve" his products specifications by using his own specially designed
"Dummy Antenna". The second problem is how to align sets in the factory,
or on the service bench, when the final users actual antenna system is not
available. The problem is that the alignment of the antenna stage of a
radio is greatly affected by the impedance of the actual antenna that is
used with the radio. The "IRE Standard Dummy Antenna" provides an
approximation of what was assumed to be a typical consumer antenna. Of
course what you really want to do is align the set with the actual antenna
attached that it is used with.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

Curious about the I.R.E. Standard Dummy Antenna
 

It's really fun because those slugs are
WAA-AAY up in there, and difficult to reach. You can't do it with a
non-ferocious screwdriver, or even a ferocious one -- it's too tight. You
have to reach the shaft with needle-nose. In any case, all this fun aside,
I can tinker and bring it into line -- but I still wonder why I have to do
it in the first place.
==================================
I always use tame screwdrivers which don't need to be caged.

Frank GM0CSZ / KN6WH

Curious about the I.R.E. Standard Dummy Antenna
 

On Mon, 04 Sep 2006 21:51:10 -0700, "H. P. Friedrichs"
wrote:

I gather that this circuit models a wire antenna of some type. Is this
true?

"The Institute of Radio Engineers has defined the INPUT SENSITIVITY OF
A RECEIVER as the number of microvolts required to produce standard
output when applied through a dummy antenna having the characteristic
impedance of the antenna with which the receiver is intended to
operate, to the input terminals of the receiver." Boonton, 1954

73's
Richard Clark, KB7QHC

Curious about the I.R.E. Standard Dummy Antenna
 

H. P. Friedrichs wrote:
I am interested in the origins and purpose of the "IRE (Institute of
Radio Engineers) Standard Dummy Antenna," as used during the alignment
of radio receivers.

I first came across this circuit in some old Hallicrafter's
documentation, which described the alignment of a particular radio. The
"IRE Standard Dummy Antenna" consists of four components--- a 200pf cap
in series with a 20 uH inductor, which links the signal generator to the
receiver's antenna input. A 400 pF cap in series with a 400 ohm resistor
is connected in parallel with (shunts)the inductor.

I gather that this circuit models a wire antenna of some type. Is this
true? What is the import of the component values and how were they
arrived at? I modeled the circuit in Spice and graphed the transfer and
impedance curves but it is not entirely clear to me what benefit there
is to using this circuit.

I've also Googled this and found some references here and there, but
nothing explains the "why" of it.

Is there anyone who can shed light on this?

73
Pete
AC7ZL

hpf (at) gainbroadband (dot) com

I built an I.R.E. dummy antenna recently to perform an alignment on a
Hallicrafters S-120. It is cobbled together on a small perfboard with
copper lands around the holes, has a length of coax with a male BNC
connector to go the the sig-gen and a female BNC connector to attach the
sig-gen lead.

I will post a pic on a.b.p.r when I can.

Bobby
KC9IHK

Curious about the I.R.E. Standard Dummy Antenna
 

Pete, I was curious about the dummy antenna, too. Some time ago I
modeled it and checked the impedance looking back into the output leads
with a 50-ohm generator at the source. The results are he

http://users.tns.net/~bb/dummy.htm

Before I did the model I figured that the dummy antenna was trying to
simulate a certain length of wire on shortwave. But you can see that
the magnitude of the output impedance (upper plot) is around 400 ohms
throughout the shortwave part of the spectrum. Down in the broadcast
band the network becomes almost purely capacitive, which is what a
short wire will do.

In fact, at 500 and 1000 kHz (the two spots I checked), the dummy
impedance is almost exactly that of a wire that runs 15 feet vertically
and then 90 feet horizontally over perfectly conducting ground. I
imagine they had a 100-foot wire in mind, a figure I think I've seen
recommended for BC antenna length in the old days.

So I think the network is intended to be 400 ohms resistive at SW and
at BC behave as a 100-foot wire would. I align radios with the network
and then at installation I tweak the antenna capacitors, if they are
easily accessible, on the actual antenna.

Brian

Curious about the I.R.E. Standard Dummy Antenna
 

Brian--

Your spice simulation looked familiar...VERY familiar. As it turns out,
I had plotted similar curves and happened to have used Microcap as well!
I was just not sure I understood the relationship between the transfer
function I saw and some kind of physical antenna.

Your comments make sense, though I do have one question: How did you
calculate the impedance of the antenna with the shape and dimensions
that you described?

73
Pete
AC7ZL


Brian wrote:

Pete, I was curious about the dummy antenna, too. Some time ago I
modeled it and checked the impedance looking back into the output leads
with a 50-ohm generator at the source. The results are he

http://users.tns.net/~bb/dummy.htm

Before I did the model I figured that the dummy antenna was trying to
simulate a certain length of wire on shortwave. But you can see that
the magnitude of the output impedance (upper plot) is around 400 ohms
throughout the shortwave part of the spectrum. Down in the broadcast
band the network becomes almost purely capacitive, which is what a
short wire will do.

In fact, at 500 and 1000 kHz (the two spots I checked), the dummy
impedance is almost exactly that of a wire that runs 15 feet vertically
and then 90 feet horizontally over perfectly conducting ground. I
imagine they had a 100-foot wire in mind, a figure I think I've seen
recommended for BC antenna length in the old days.

So I think the network is intended to be 400 ohms resistive at SW and
at BC behave as a 100-foot wire would. I align radios with the network
and then at installation I tweak the antenna capacitors, if they are
easily accessible, on the actual antenna.

Brian

Curious about the I.R.E. Standard Dummy Antenna
 

Brian wrote:
The results are he

http://users.tns.net/~bb/dummy.htm

Nice charts, thanks for doing those.

So I think the network is intended to be 400 ohms resistive at
SW and at BC behave as a 100-foot wire would.

Pretty much what I said initially. A uniform high impedance.
As others pointed out the output attenuator of most "service"
grade signal generators at the time was all over the place.

What I find amazing is that what we can do with Spice in a few
minutes was painstakingly done by hand until the they got the
results they desired. Then published as a "cook book" standard
for others to use.

The bottom line was that you could introduce a signal into the
receiver under test without undue de-tuning of the tuned circuits.

Jeff


--
RESTRICTED AREA. Anyone intruding shall immediately become subject to
the jurisdiction of military law. Intruders will be subject to lethal
force, without warning, and on sight. USE OF DEADLY FORCE IS AUTHORIZED
under the Internal Security Act of 1950.

Curious about the I.R.E. Standard Dummy Antenna
 

Your comments make sense, though I do have one question: How did you
calculate the impedance of the antenna with the shape and dimensions
that you described?


With a computer program.

Brian

Curious about the I.R.E. Standard Dummy Antenna
 

Pete, I forgot to mention the reason I believe the IRE dummy antenna
tries to look like a 400-ohm resistive load at shortwave instead of a
certain length of wire. You can see why he

http://users.tns.net/~bb/antlen.gif

This is an old RCA chart showing the behavior of an end-fed wire for
lengths to 125 feet. It indicates the many resonances and
antiresonances a short wire can exhibit. Since the antenna impedance
and the resulting performance vary so markedly with wire length, and
because it would be unrealistic to expect all listeners to use one
particular length, I think the dummy antenna is just intended to
roughly match the input impedance of a typical radio. I'm not sure
about consumer radios, but old communications receivers all seem to
have a specified input impedance of either 300 or 400 ohms.

On the broadcast band, any wire shorter than about 150 feet will look
capacitive. It won't exhibit the resonances you see in the chart at
shortwave. So even if the wire is shorter than the 100-foot length the
dummy antenna seems to model and exhibits a higher capacitive
reactance, it won't affect the radio's RF tracking that much. On the
broadcast band, most radios seem to use rather loose antenna coupling
to minimize mistracking. This allows them to accomodate antennas of
various length. There is an interesting discussion about antenna
coupling strategies in the Radiotron Designer's Handbook.

Brian

Curious about the I.R.E. Standard Dummy Antenna
 

GREAT info, that's why I lurk here often.

Just one teensy question, though...is this polarized?,
e.g. the 200pf cap is the receiver probe, the inductor
plus shunt is the signal gen connection? or versa-vice?

Thanks,
Terry Bakowski

[see you at the Peoria Superfest]


H. P. Friedrichs wrote:

I first came across this circuit in some old Hallicrafter's
documentation, which described the alignment of a particular radio. The
"IRE Standard Dummy Antenna" consists of four components--- a 200pf cap
in series with a 20 uH inductor, which links the signal generator to the
receiver's antenna input. A 400 pF cap in series with a 400 ohm resistor
is connected in parallel with (shunts)the inductor.

Curious about the I.R.E. Standard Dummy Antenna
 

Brian,

This link seems to be broken.

Pete
AC7ZL


Brian wrote:
Pete, I forgot to mention the reason I believe the IRE dummy antenna
tries to look like a 400-ohm resistive load at shortwave instead of a
certain length of wire. You can see why he

http://users.tns.net/~bb/antlen.gif

This is an old RCA chart showing the behavior of an end-fed wire for
lengths to 125 feet. It indicates the many resonances and
antiresonances a short wire can exhibit. Since the antenna impedance
and the resulting performance vary so markedly with wire length, and
because it would be unrealistic to expect all listeners to use one
particular length, I think the dummy antenna is just intended to
roughly match the input impedance of a typical radio. I'm not sure
about consumer radios, but old communications receivers all seem to
have a specified input impedance of either 300 or 400 ohms.

On the broadcast band, any wire shorter than about 150 feet will look
capacitive. It won't exhibit the resonances you see in the chart at
shortwave. So even if the wire is shorter than the 100-foot length the
dummy antenna seems to model and exhibits a higher capacitive
reactance, it won't affect the radio's RF tracking that much. On the
broadcast band, most radios seem to use rather loose antenna coupling
to minimize mistracking. This allows them to accomodate antennas of
various length. There is an interesting discussion about antenna
coupling strategies in the Radiotron Designer's Handbook.

Brian

Curious about the I.R.E. Standard Dummy Antenna
 

This link seems to be broken.


Pete, I remove temporary items from my web site pretty quickly due to
space restrictions. I tried to e-mail the chart to you but got the
following reply:


----- The following addresses had permanent fatal errors -----

(reason: 591 your host [216.86.143.7] is blacklisted by
bl.spamcop.net. No mail will be accepted)


No more midnight spam for me! Anyway, the chart is back up for a couple
more days.

By the way, on the perfboard I used to build my dummy antenna I added a
0.1 uF coupling capacitor between the signal generator input and a
second output lead with an alligator clip. This provides a 50-ohm
DC-isolated signal for IF alignment. I usually align radio IFs by
sweeping a signal at the front end, often just blasting through the RF
and mixer stages at 455 kHz. But the alligator clip is handy when I
want to drive the mixer grid directly. You can drive the grid with the
dummy network, but the 50-ohm source impedance of the direct output
ensures that the parallel impedance at the grid doesn't affect the
sweep flatness.

Brian