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RE: Question On Passband noise with IF off



Thanks for the response Gunther.
I was decoding telemetry at the time and paid very close attention to the IF
matrix. It only show the MB connected to S-TX with no other paths active. I
will check the archive to make sure I was decoding correctly. It may be one
of those strange quirks that doesn't have an answer.

> -----Original Message-----
> From: Gunther Meisse [mailto:gmouse@neo.rr.com]
> Sent: Sunday, October 05, 2003 5:44 PM
> To: gary@ridepix.com
> Cc: amsat-bb@amsat.org
> Subject: RE: [amsat-bb] Question On Passband noise with IF off
>
>
> Gary,
> You can check the telemetry archive on the web site and check the Matrix
> status at that general position within the orbit. Occasionally, when the
> transponder is turned off, and just the Telemetry beacon is on, the
> matrix has the MB routed thru the Leila to the S-Band Tx. When that is
> the case the noise floor jumps way up, even though a receiver is not
> patched through.. I have noticed it many times.. It does not represent
> any sort of a problem, just a quirk as the result of the configuration.
> It is most dramatically noticed near Perigee..
> Regards,
> Gunther Meisse
> W8GSM
>
>
> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On
> Behalf Of Gary Gonnella
> Sent: Sunday, October 05, 2003 5:40 PM
> To: Amsat-Bb
> Subject: [amsat-bb] Question On Passband noise with IF off
>
>
> I have noticed a curious thing on the AO40 Passband. Under normal
> conditions when the squint is low I hear the pass band noise at about
> 3db or so above the receiver noise. Today (9/05/03) I noticed that after
> the transponder was shut off and the bird was at a low altitude there
> was a significant noise level on the output. The readings were taken at
> MA 244 with an altitude of about 7000 miles and a squint of about 50
> degrees. The telemetry at this time showed that no receiver was
> connected to the transmitter.
>
> My understanding of the noise floor is that is the noise from the
> receiver being passed through the IF matrix and being "repeated" at a
> low level. Under this assumption there should be no "repeated" noise
> floor on the S2 transmitter when the IF matrix is off.  So the question
> is this noise coming from a connected receiver or is this some noise
> being generated in the S2 transmitter?
>
> BandScope images can bee see on my site here
> http://www.w6ryo.com/passband.htm
>
> Any information on this would be appreciated.
>
> Gary Gonnella W6RYO
> http://www.w6ryo.com
>
>
> ----
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