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Re[2]: FO-29 [qrm possibly located]



   >I believe I may have heard the same QRN (or another one located in Central
   >America) at about 435.800 when I was searching for the beacon on FO-29. The
   >bird was making a S->N pass and was mostly over the Pacific and C.A.  It
   >didn't sound like repeater traffic, though, it was more like re-transmission
   >of a daytime soap opera.

   This sounds like Cable TV leakage.  Cable channels are in this frequency
   range.

Well, we have an ATV station in San Rafael operating on Cable Channel 59.
The main components of appear S9+ at 433.25 and 437.75, with lots of little
spurs in other parts of the satellite sub-band (rendering AO-27 unusuable
anywhere vaguely sight-of-sight of said station).  On the other hand, FO-20
and FO-29 both have inverting linear transponders from 145.9-146 MHz to
435.8-435.9 MHz (+/- >10 KHz).  So if this were on the uplink, it would be
close to 146 MHz.  The repeater previously discussed is on "145.940 -600"
which i predict would appear at 435.86 (+/- doppler).

I tried listening for FO-29, but that bird is 1W distributed over a 100 KHz
passband and that may not be enough power to be heard with an HT and a AO-27
class antenna.  But i did find a spur from the the ATV station (it did not
change direction or frequency, e.g. no doppler) at roughly 435.84 MHZ, but
that's still 40 KHz away from your FM signal.  So no easy answers on there.

It may be that said ATV station isn't exactly on the CATV channel 59, but
close enough that a cable-ready TV or VCR can pick it up readily, in which
case, 40 KHz is trivial.  After all, a TV signal is normally 6 MHz wide.
(And how a bandplan can specify ATV Video Channel 2 at 434.000 and ATV Audio
Channel 2 at 438.500 [http://www.sharkk.com/ncalplan.htm#70 Centimeter],
[http://www.sharkk.com/scalplan.htm#70 Centimeter] without overlapping
the satellite sub-band escapes me entirely... Albeit i understand that the
Northern California 70cm band plan may be in the process of being revised.)
But the spurs i am hearing appear to be FM modulated but have a strong 60Hz
harmonics (presumably vertical retrace) in absence of other audio traffic.

A couple of easy questions:  Does the QRM exhibit doppler and/or changes of
direction?  Is a absent when no amateur satellites are overhead?  If either
answer is "No", then it's probably terrestrial interference. Try DF'ing it,
especially if you or someone you know has a portable beam such as an 'Arrow'
or a comparable antenna used for AO-27.  But do be aware that if it's CATV
leakage, there could be more than one emission site and DFing may be more
challenging that way.  73's and good luck!

	    			    -- KD6PAG
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