[Milsurplus] [spam?] LO DFing, the myth that never dies!

[Ray Fantini]

Who's intelligence agency is going to use a cheap receiver? I would assume a common late thirties early forties intercept receiver to be a HRO-M or equal unless we are talking about some of that suit case type stuff and I have no idea of its technical envelope.
Ray Fantini

-----Original Message-----
From: Dave Maples [mailto:dsmaples at comcast.net] 
Sent: Wednesday, December 02, 2009 4:39 PM
To: Ray Fantini; milsurplus at mailman.qth.net; mikea
Subject: RE: [Milsurplus] [spam?] LO DFing, the myth that never dies!

All: It's not necessarily true that receiving the LO of another receiver
tells you nothing.  If power supply regulation is not that good (typical for
a cheap receiver) the LO may be FM'd or AM'd or both with the output of the
detector, particularly if it passes through some power amplifier.

Dave WB4FUR

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net]On Behalf Of Ray Fantini
Sent: Wednesday, December 02, 2009 3:57 PM
To: mikea; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] [spam?] LO DFing, the myth that never dies!



Not to be demeaning or as a insult but as a question that I would propose.
If you receive the LO of another receiver what will that tell you? Assuming
you know the IF frequency and if the receiver is signal or double conversion
perhaps you can determine the operating frequency of the receiver but you
cannot determine what if anything it is receiving. There is value to knowing
that someone may be monitoring a given frequency but would assume once again
by the mid thirties every intelligence agency assumes their radio traffic is
monitored and what advantage is there to be gained in confirming this? And
along this line all listening post set up to monitor embassy traffic are way
more interested in traffic transmitted from the embassy as official traffic
and possibly by covert devices they may have planted on the grounds. Perhaps
if you think clandestine or agent stations are operating in your area and
you know where the central receive site is you can then determine the
operatin
 g frequency of the rogue station and this is what they were listening to?
After you know the frequency of the rogue they can be plotted and located?
Ray Fantini

Let's stipulate that you're right, Ray.

What were Peter Wright and his friends listening to, then, with their
specially-built TRF receivers?

--
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin
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