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Re: "spontaneous" LEILA activation



Hi Wayne:

    I to am picking up random LEILA sirens going off (or should I say on?) for no
apparent reason.  A couple of times I happen to sit on certain frequencies just
listening to static while doing something else in the shack and LEILA pops
in there. When I have my spectrum analyzer on I see most of this action
happening around 2401.400 on up. Sometimes I look at the scope and see
LEILA going off all over the place nonstop above .400 when there is no action
on those frequencies.

Also every now and then when the squint is good and i'm getting a good S-8 or better signal
on the beacon I am picking up what sounds like random static pops on the transponder
downlink. When I tune off the edge of the transponder the random static pops and the
little noise floor that I can hear disappears which seems to indicate that its coming
form the bird. Can anyone confirm this? Could this be the trigger?

73
Tom / N7HXP
Tacoma
mjrtom@home.com

----- Original Message ----- 
From: "Estes Wayne-W10191" <W10191@motorola.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, September 24, 2001 12:50 PM
Subject: [amsat-bb] "spontaneous" LEILA activation


> I frequently hear unexplainable LEILA sirens in the vicinity of 2401.400 MHz
> where there is hardly ever any transponder activity.  Once this weekend I
> was tuning across the transponder and heard the LEILA siren go nonstop for
> more than 90 seconds.  I don't know how long the siren was going before I
> stumbled onto it.  When I hear "spontaneous" LEILA sirens I verify that my
> uplink signal is notched, just to ensure that nobody is uplinking a
> recording of the LEILA siren.
> 
> Could there be a powerful U or L-band terrestrial interference source that
> transmits brief pulses or high-speed data that is not audible on the AO40
> downlink?  What other theories could explain why LEILA seems to activate for
> no apparent reason?
> 
> Wayne Estes W9AE
> Mundelein, IL, USA
> 
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