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

"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

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.

"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

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.

"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

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/

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/

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

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