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Fw: Mystery of Radar Signals AO-40



Subject: Mystery of Radar Signal interference on  AO-40



     Several of us who are active on AO-40  continue to observe the effects
 of apparent radar signals on AO-40.  This interference is very noticeable
 on SSTV pictures.  It appears that Leila is  possibly being
 triggered by radars.  The interesting thing is that  when communicating
 through AO-40 the volume control on the receiver of the  transceiver
sending
the picture can be advanced and the
 radar signals can be clearly heard at a frequency of 435.647 MHz,  for
 example.
    We can also  hear and see the  effect of  the radars
 when we receive ATV on 439.25MHz.  The radar signals can be heard from
about
 432 to 440 MHz. It is also observer that this interference is possibly
local and is not always present.
     The question is, if we hear the radar on the AO-40  uplink freq, why
can't we
 hear it on the 2401 downlink. across the passband??   Apparently Leila does
 hear it and responds?
     On SSTV the interference is apparent on most pictures.  This includes
 those from Japan, New Zealand and Australia and within the USA.  However it
 seemed to be lessened on at least a couple of pictures I  have received
from Gerrmany.
The radar pulse duration is estimated very roughly with durations up to 10
to 15 msec.
 This was determined by measuring the short interference streaks on  SSTV
pictures.
     Any idea where the radars are located?  Are they also on 1200MHz ,
possibly on 2401MHz?  Are
 they by any chance out 22,000 miles in the Clark belt area?
     Comments or observations  would be very much appreciated.  Thanks,

 Farrell Winder, W8ZCF, Cincinnati, Ohio

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