"Steve Nosko" wrote in message
...
Actually, if there is an *easy* way, I'd sure like to know!

I started my DF'ing in the Navy in the late 60's, so I'm no slouch.
This is a very sticky problem; few ways to do this. All phase systems
(Doppler, TDOA) require the signal to be well centered in the IF and a
well
behaved IF to boot. The amplitude systems (beam, single / dual cardioid)
are better for this, but the sweep-width of this signal makes the beam
less
effective due to the change in gain as you get off the design freq.

If I had the time, I'd modify a wide band FM receiver (like a broadcast
receiver 88-108) with a *really* aggressive AFC so it would follow the
bogie
along. Then a TDOA should work. Actually any would be better with this
receiver, but I would have to do a little characterization across the
expected freq range first.

I think *any antenna* and a spectrum analyzer watching signal strength is
the best bet...already done some of that. The biggest problem is that it
is most active when we have the least time to hunt.
Steve





"Crazy George" wrote in message
...
Ed:

I think Steve would be interested in hearing a methodology for DFing a
non-stationary signal, as would I. I have tried to track one of these
spurs
with a receiver while simultaneously attempting to get a bearing, and
gave
up. The Doppler DF systems need it in the passband and frequency stable
for
at least one "revolution" of the virtual antenna, which doesn't happen,
so
let's hear what works.

--
Crazy George


I agree with Steve's observations (although I prefer that he bottom-post),
but I would still try to keep the process simple.

First, you know the very limited frequency range of the offending signal
(you said it slowly drifts across your repeater input at 145.41 MHz). So
that means you know which way it drifts, about how fast the frequency slew
is, and about how far it shifts. Further, you know the characteristic
modulation on the signal. And, to make it even easier, the signal isn't
playing tricks on you to spoof your search. Finally, you must have some idea
by now as to when the signal is most likely to be present.

Time to get a directional antenna (Yagi, log periodic, a loop resonant to
145 MHz, even an inefficient horn) and look for the signal. I would use a
spectrum analyzer (those HP boxes are too big and heavy, so look for a
Leader or Anritsu. Why not turn this into a real learning experience? Why
not build a 2 meter version of the Poor Man's Spectrum Analyzer into a
briefcase, maybe updating the display by using a small laptop?

As a first assumption, I suppose we can assume that the offending signal
isn't in a vehicle. So get out and grab a bearing when you can. Obviously,
you have to be prepared to get into the field quickly and efficiently to
make your observations. After a couple of bearings, at least you will guess
which side of town to look first.

Hey, if this was easy, then T-hunts would be no fun, and clandestine radio
would be a short path to a bullet.

Ed
wb6wsn