Today I had 7 scanners setup, each scanner setup to scan a 25 MHz
segment of the 225-400 MilAir band. Everything was going fine up until
1048 hrs EDT. 5 of the 7 scanners stopped with what sounded like a data
signal. Here are the freqs which had the very same transmission:
225.0000
275.0000
300.0000
325.0000
375.0000

The transmission lasted for about 3 minutes and quit. Very strong
signal on all 5 freqs. I’ve done many searches using 7 scanners before
and never had anything like that happen. Anyone have any ideas of what
this was?

George
http://www.MilAirComms.com

M 1 wrote:
George,

I know Novice are limited to 25 Watts (PEP) for CW, RTTY, Data, MCW, Test,
SSB(Phone) and Image transmissions on freqs between 222.0 - 225.0 Mhz.

What about computer interference from a AMD K6 3D and Pentium II. They
operation at 375.0 Mhz.

Consider this, System-B S-Channels and Systems-G H-Channels cover a
frequency range from 230.0 to 470.0 Mhz FM. You might have detected a
Amateur TV Test Signal or a Marker for video surveilance.

ml


I don't think it was interference from within my house or I would have
this problem all the time. I do searches like this several times a week
and this was the first I received the same signal every 25 MHz.....

George
http://www.MilAirComms.com

GeorgeF ...

^ ... I had 7 scanners setup, each scanner setup to scan
^ a 25 MHz segment of the 225-400 MilAir band.
^ Everything was going fine up until 1048 hrs EDT.
^ 5 of the 7 scanners stopped with what sounded like a
^ data signal.

^ Here are the freqs which had the very same transmission:
^ 225.0000
^ 275.0000
^ 300.0000
^ 325.0000
^ 375.0000

^ The transmission lasted for about 3 minutes and quit.

Did the other two scanners cover 250.0 and 350.0?

Coincidentally, while I was reading your message (abt 1825Z) I heard a loud
klaxon-like sound coming from one of my scanners. By time I got over to the
scanner the sound had stopped but there was still a carrier holding one of my
39MHz frequencies open. The klaxon, which did sound like a data signal, only
sounded three times for a total duration of about five seconds. It's probably
not related to what you heard.

Frank

GeorgeF om...

^ ^ 225.0000
^ ^ 275.0000
^ ^ 300.0000
^ ^ 325.0000
^ ^ 375.0000

So the bracketed frequencies all simultaneously received the same signal:

Scanner 1 [225]- 250 MHz
Scanner 2 250-[275] MHz
Scanner 3 [275]-[300] MHz
Scanner 4 [300]-[325] MHz
Scanner 5 [325]- 350 MHz
Scanner 6 350- 375 MHz
Scanner 7 [375]- 400 MHz

I'm guessing that the scanners were hit as follows:

Scanner 1 225 MHz
Scanner 3 275 MHz
Scanner 4 300 MHz
Scanner 5 325 MHz
Scanner 7 375 MHz

Each the first frequency in the set. It looks to me like something interfered
internally with the scanners, but you said that the signal being received was
data. So I don't know.

Frank

I'm guessing that the scanners were hit as follows:

Scanner 1 225 MHz
Scanner 3 275 MHz
Scanner 4 300 MHz
Scanner 5 325 MHz
Scanner 7 375 MHz

Each the first frequency in the set. It looks to me like something interfered
internally with the scanners, but you said that the signal being received was
data. So I don't know.

Frank


Yep you pretty much got it correct. Without question it was some type
of data. Also to elimite the possilblity of interference between
scanners I had turned all but one off and still got the interference on
that last scanner on 375.000. So I'm pretty sure it wasn't interference
between the multipul scanners. Plus I've run this same search, same
ranges, same antenna, same multicouplers, and same scanners and ever had
it happen before....just strange....
George
http://www.MilAirComms.com

GeorgeF om...

Frank:
^ Each the first frequency in the set. It looks to me
^ like something interfered internally with the scanners,
^ but you said that the signal being received was data.

GeorgeF:
^ Without question it was some type of data.

In my limited experience the only thing that fits this situation is jamming.
I got to observe this being done by a very experienced jammer while my ship
was off the coast of Vietnam. High power noise at regularly spaced intervals
can jam an entire band.

A similar tactic is counter-jamming. I observed this same guy plug a teletype
into a common circuit and transmit useless data at high power. When the North
Vietnamese started jamming that frequency he transmitted the real data at low
power on another circuit.

So my revised guess of what you heard is that it may have been part a large
scale exercise in jamming tactics. Perhaps there was another unit involved
that was suppose to practice counter-jamming at the same time. If all nearby
frequencies were unusually quiet just before and just after the noise then I
would expect that it was a scheduled exercise.

Frank

"RadioNerd" wrote in message
...
George,

I've been enjoying your posts on the groups and have visited your
website quite a few times.

snipped for brevity

I too have enjoyed your posts George and this one by far has got my mind
going. Gotta get me some more scanner to do my own searches of different
bands like you do with Mil bands....

Sounds like you've run across a spread spectrum encrypted signal. I
hear 'em here occasionally. I'm south of Washington DC near Quantico
Marine Corps base, the CIA and a huge remote transmitter site used by
the Pentagon. (It's also a 'numbers station' transmitter site, but
they don't exist, do they?). As per typical CIA and Pentagon
operations, they use any radio frequency they want to- the ham bands,
shortwave broadcast bands, military bands and in between television
channels a lot. I've been next to the remote Pentagon site with my
OptoScout and my R-10 and had it come up anywhere between 200 and 500
MHz with two to ten channels spaced from five to forty MHz apart of
what sounded like medium baudrate data or white noise or a strong dead
carrier which lasted anywhere from a minute to ten minutes at a time
and then went down.

WHOA!! Very interesting!

-RF
http://www.Police-Scanner.info