How do you isolate a signal?
 

I have a funny problem here. I am using my dual band radio, a Kenwood
TM-G707 as a simple scanner and I have a problem in isolating a signal. If I
open the squelch manually most of the way, I receive a signal from 400 to
523 mhz everywhere. This signal is on 24 hours a day but seems to be
modulated only part of the time. When it is modulated, in FM mode, I hear a
tv station crew doing their stuff to mount a program. I can hear the
producer giving orders to the cameramen and also the script girl. The mikes
are on all the time and not switched. I can't identify what station it is
but this has been going on for many years. what I would like to do is
identify the exact frequency they use but they splatter all over the band.
Is there a way to really zero on them? Since I live in the Montreal area, it
could come from everywhere but Iknow it's not coming from my town because no
one does that kind of free lance work around here. I am really baffled and
would appreciate some sugestions. Thanks.
Mike.

How do you isolate a signal?
 

Hi Mike

An intermod product? Fundamental overload? Modern broadband design
amateur radios arent renown for good selectivity in strong signal
environments... I doubt they "splatter all over the band", its most
likely your receiver possibly in tandem with some other strong signal
mixing in the front end. It may even be coming direct to the IF.

First suggestion is to use a smaller antenna (thinking its an overload
situation). A directive antenna would be next with an inline attenuator
and scan around. Keep in mind that the signal you want to hear may not
even be in the radio's normal band coverage. Next is to try a different
radio (design) and scan with that. It is probably also worthwhile
listening to determine who they might be, then do a online database
lookup (if Canada has it) for that organisations name!

Cheers Bob VK2YQA


VE2CJW wrote:
I have a funny problem here. I am using my dual band radio, a Kenwood
TM-G707 as a simple scanner and I have a problem in isolating a signal.

How do you isolate a signal?
 

VE2CJW wrote:
I have a funny problem here. I am using my dual band radio, a Kenwood
TM-G707 as a simple scanner and I have a problem in isolating a signal. If I
open the squelch manually most of the way, I receive a signal from 400 to
523 mhz everywhere. This signal is on 24 hours a day but seems to be
modulated only part of the time. When it is modulated, in FM mode, I hear a
tv station crew doing their stuff to mount a program. I can hear the
producer giving orders to the cameramen and also the script girl. The mikes
are on all the time and not switched. I can't identify what station it is
but this has been going on for many years. what I would like to do is
identify the exact frequency they use but they splatter all over the band.
Is there a way to really zero on them? Since I live in the Montreal area, it
could come from everywhere but Iknow it's not coming from my town because no
one does that kind of free lance work around here. I am really baffled and
would appreciate some sugestions. Thanks.
Mike.



Hi, Mike -

I've heard a similar signal just above the 70 cm band (above 450 MHz) but I
don't remember the exact frequency. It was a local AM radio station using
that frequency for remote broadcasts like, say, a little league baseball
game. While not actually rebroadcasting the game, I could hear all sorts of
stuff going on. They even occasionally used the frequency as one half of a
duplex communications link as an aid in getting everything set up. The other
half of the duplex link was the AM radio station!

Sounds like you might have something similar in your area, but perhaps the
signal is so strong that your receiver is overloading so as to make the
signal appear wide. Or, maybe they're also broadcasting the video as well.
As you know, video is very wide (but not 123 MHz wide).

You could try a different location to monitor them and see if the signal
narrows down some. Otherwise, try to zero in on the voice frequency.

Just a guess.

Cheers,
John

How do you isolate a signal?
 

On Fri, 14 Jul 2006 00:10:34 -0400, "VE2CJW"
wrote:

I have a funny problem here. I am using my dual band radio, a Kenwood
TM-G707 as a simple scanner and I have a problem in isolating a signal. If I
open the squelch manually most of the way, I receive a signal from 400 to
523 mhz everywhere. This signal is on 24 hours a day but seems to be
modulated only part of the time. When it is modulated, in FM mode, I hear a
tv station crew doing their stuff to mount a program. I can hear the
producer giving orders to the cameramen and also the script girl. The mikes
are on all the time and not switched. I can't identify what station it is
but this has been going on for many years. what I would like to do is
identify the exact frequency they use but they splatter all over the band.
Is there a way to really zero on them? Since I live in the Montreal area, it
could come from everywhere but Iknow it's not coming from my town because no
one does that kind of free lance work around here. I am really baffled and
would appreciate some sugestions. Thanks.
Mike.


Mike

I am an ex-broadcast TV worker. To me it sounds like a studio talkback
system that is left on all the time - not uncommon in regularly used
control rooms - but only has modulation when in use. From what you
describe of your neighbourhood it is unlikely to be front end overload
on your Kenwood.

To help track down the source it may be possible to figure out what
sort of programming is being produced by listening to the talkback; if
the same stuff happens at the same times of the week/day it is
obviously a regular show of some kind.
It is most likely to be a prerecorded show; the only live broadcasts
are news programmes and sporting events and the timing will give a big
clue.
"Run tape. OK, we got three minutes, reset for the singing sheep".

If it is a regular show, the direction will be fairly laconic because
the crew will be doing the same stuff over and over again - but you
might get the presenters' first names:
"Two, tight closeup on Tom. Three, loose two on Dick and Harry".

If it is a game show, anything up to six progarmmes might be recorded
in a day:
"Next is programme three. Autocue, can we change line four to 'our new
defending champion from last week is John Doe' "

Either way, your next step should be to Google TV production companies
in the Montreal area, starting close and working outward. I suspect
there will not be many with a regularly used studio. It is a small
community so a very few calls may well help you zero in on the source.

In each case ask for the technical director and explain what you are
receiving; in my experience he would be very concerned about the
emission and take steps to suppress it as quickly as possible for a
variety of reasons:
"OK three, gimme a two shot. One, frame a single on that visiting
political asshole once makeup has made him vaguely human".

Good luck.

Pete