[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

"spontaneous" LEILA activation << I hear the pulses here too>> ?? A radar or ranger?? Lband or U band???



I wrote but did not send a note about this:
That I could tune towards the satellite, and see 3 db of transponder noise
raise the
S meter, squint within 5 degrees, and noted impulses coming from the
transponder downlink.    I can within 1/2 second, move the dish with a fast
motor,
and see the noise floor go back down, and see the impulses go away.
They are so strong they yes, trigger the leila, and cause me to need my
noise blanker
as they chop out bits of transponder audio. The noise blanker seems to limit
it well,
but one can hear the impulses cause a slight FM modulation of the signals in
the
transponder, because the pulses (about 1 or 2 per sec) saturate the
transmitter up there,
because the AGC is not following the impulses. I usually do hear the pulses
on west
passes with Cal in the footprint........and doesnt matter what freq it
affects the whole of
the transponder.

 I could detect as little as 6 watts eirp up into the sat.
One can find the source by observation, when do the pulses first appear,
perhaps
when a particular location rises? I have been in LA area and heard about the
radars
they have there, they are not radar, they are ranging pulses from offshore
platforms,
The Guys in LA area know what they are. They bother the repeater inputs
between 441 and 445.
which in that area are low and outputs are high.
Also I thought the impulses were a local source, until I noticed they went
away when
either the transponder is off, or when I point away from it.
The pulses may be going up on the L band link - the pulses are not always
there.
I need to record them in very wide am detector,  without agc, like a TV IF.

Now you guys have put 2 and 2 together....that this is what the leila is
chasing.
Also it seems to chase after the higher gain parts of the trasnponder.



----- Original Message -----
From: "Estes Wayne-W10191" <W10191@motorola.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, September 24, 2001 2:50 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
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home