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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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