I'll only say that it is interesting that the first comments were about the
grammar not the content.

Interesting story Walt. That's what I call an ending!

Brief story 1
The apollo recovery ships had problems in the radars from high power HF
transmitters and the rusty deck railing chains.


Brief story 2...well not so brief.
To solve a problem in a 150MHz car telephone in a Caddy and one on a
motorcycle, I developed a method for finding what I dubbed "environmental
desense" of a similar nature. This amounted to the transmitter being
modulated, in its _field_ by near-by noisy joints in the car body or the
motorcycle seat springs. This produced virtual noise sidebands on the
transmitter. This "modulation" extended out to the receiver frequency. The
receiver used the same antenna, thus easily picking up this new "noise
modulation.
This is an extension of what I had called "the Screwdriver Effect" in my
early 2-way repair days. you are listening to a rather close transmitter
(or maybe not so close) and you simply rub a screwdriver across another
nearby piece of metal and you hear noise on the received signal. Same
effect - field modulation.
To explain in more detail...
1- EVERYTHING conductive is an antenna (receiving).
2- Everything has RF current in it from every transmitter (even YOU).
3- These "everythings" therefore produce small RF fields of their own,
from these currents.
4- These fields sum with the original field.
5- If two of these "everythings" come into contact, there can be a
change in current due to the new physical arrangement (current through the
new connection)
6- This change also changes the resulting fields from the "Everythings"
7- This changes the total resulting field.
8- this is just like a change in the original field and just like a
change in the transmitted signal.
9- SO... this is received just like some similar modulation on the
original transmitter. Try it, but the screwdriver part has to be near the
receive antenna and the main signal not so strong that the noise is too far
down. 2M FM may the best place to try.

Noisy screwdriver contact...noisy received signal

73, Steve, K,9.D;C'I



"Walter Maxwell" wrote in message
...
Messed Up Ground Radials Can Generate Spurious Signals

In 1948 I was the consulting engineer for the proposed first AM
broadcast
station in Mt. Pleasant, Michigan, obtaining a construction permit and
license
for WCEN, 500 watts on 1150 KHz. Using a National HRO receiver, I was
performing
a hands-on search for an available frequency for the new station, when I
encountered an interesting and unusual signal that was entirely out of
place in
the AM broadcast band-a CW Morse-code station illegally transmitting
five-letter-word code groups at 30 words per minute. The illegal signal
was S9
+40 dB on 1297.8 KHz, producing a 2200 Hz beat-note with the 1300 KHz
frequency
of WOOD, Grand Rapids, thus producing a an audible CW signal with the
receiver
BFO disabled.
The format of the coded messages appeared to be military, IDing as
NSS. We
know that NSS is the flagship station of the U.S. Navy in Annapolis, MD,
but in
the AM broadcast band? It appeared that either an NSS transmitter was
producing
a spurious emission, or a station using NSS as a fraudulent call sign was
operating clandestinely in the AM broadcast band. I deemed it important to
find
out which.
As a former FCC monitoring officer at the Allegan, Michigan
monitoring
station, the next step was to report the situation to the Allegan station.
Although Allegan was 90 airline miles away, the monitoring personnel there
could
not hear the spurious signal, even though it was S9 +40 dB at Mt.
Pleasant. I
let the FCC monitors hear the signal through the telephone, but they still
heard
nothing on their receivers tuned to 1297.8 KHz. Thus the signal must be of
local
origin near Mt. Pleasant, and not from NSS. However, to be on the safe
side, FCC
notified the Navy of the spurious signals, and the NSS operators began
combing
all their transmitters for spurious signals, and found none. The situation
is
now becoming even more strange.
I then copied five minutes of the coded text and sent a copy to the
FCC,
who relayed it to NSS for comparison to their transmissions. The situation
is
now both perplexing and frustrating, because the text I copied on 1297.8
KHz
agreed exactly with a transmission that had been made by NSS. How could
that
signal have been transmitted on 1298.7 KHz if no spurious signals were
emanating
from NSS? But it's not likely to have been a fraudulent station. What
then?
A partial answer came shortly thereafter. As I resumed the search for
a
useable frequency for the new station, I proceeded downward from 1298.7
KHz,
going through 1280 KHz and hearing WFYC, Alma, 1000 watts, 15 miles away,
also
S9 +40 dB. But on continuing further downward I immediately came across
another
S9 +40 dB thumping CW signal. I switched on the BFO and discovered the CW
was
also a five-letter-word coded transmission at about 30 wpm, the same as
NSS. I
retuned to 1298.7 KHz and the NSS signal was also there, as before. So I
cranked
up a second receiver to monitor both frequencies simultaneously. Surprise!
Both
frequencies were showing identical simultaneous transmissions. I then
measured
the frequency of the lower-frequency signal-1262.2 KHz. Voila! The higher
CW
frequency was 17.8 KHz above WFYC's 1280 frequency and the lower CW
frequency
was 17.8 KHz below WFYC's frequency. A quick reference to the Berne
frequency
listing showed NSS assigned to 17.8 KHz. This situation now appeared to
indicate
something very wrong going on at WFYC. The low-frequency world-wide
ground-wave
signal from NSS was apparently somehow mixing with the signal from WFYC,
and
producing the 1297.8 and 1262.2 sum and difference frequencies. But what
non-linear device in WFYC's system could perform that mixing? Don't know,
but I
reported this new information to the FCC and that was the last I heard of
the
situation.until.
Fast forward now to 1955. I was now employed as an electrical
engineer at
the RCA Laboratories, the David Sarnoff Research Center in Princeton, NJ.
An
assignment took me to Washington, D.C. to attend the annual conference of
the
NAB, the National Association of Broadcasters. President Dwight D.
Eisenhower
gave the keynote address. However, one of the technical forums was
presented by
Jack Young, Chief Engineer of the RCA Broadcast Division. His topic was on
the
solution of mutual interference between two broadcast stations in Los
Angeles,
KFI and KNX.
It seems that in a section of the Los Angeles area it was impossible
to
hear one of these stations without hearing both simultaneously-when tuned
to 640
KHz for KFI, both KFI and KNX were heard, and when tuned to 1070 KHz for
KNX,
both KNX and KFI were heard. Young was assigned the task of determining
the
cause of the interference and eliminating it. To make a long story short,
he
discovered that there were ancient and rusty oil well derricks in the
affected
area. Currents from both KFI and KNX transmissions were being induced in
the oil
well towers, and the rusty joints were acting as mixers for the two
frequencies,
producing both the sum and difference frequencies, as well as re-radiating
both
signals on their original frequencies. When the derricks were removed the
interference stopped.
So how is this incident relevant to the NSS problem? Well, at the
conclusion of Young's presentation I had the opportunity to talk with him,
and
because of the similarity of the problems, I told him of my discovery of
the NSS
signals appearing in the AM broadcast band. Talk about coincidences! He
was
surprised and excited to learn that I had discovered the NSS problem at
WFYC,
because he was the one assigned to determine the cause of the problem. He
had
never been told how that problem originated, or how the problem had been
discovered.
He then explained that he had found the ground radial system under
the WFYC
antenna a horrible mess. Cold solder joints throughout, and far ends of
the
radials hanging loose in the water of the nearby Pine River, establishing
the
non-linear mixer condition that resulted in the sum and difference
frequencies
being generated between the NSS and WFYC signals. Cleaning up the
messed-up
radials ended the appearance of the NSS signals in the AM broadcast band,
thus
concluding an interesting journey.

Walt, W2DU