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RE: Mystery Noise floor on AO-40



Hi all
I have checked the orbit in question for ur location actually Günther,
and i have
made a graph which i have sent directly to you as a JPG picture.

>From here you can see, that actually the signal from AO-40 has an
increase (a peak)
exactly between MA240 and MA250 on that day, due to the combination of
increasing squint, increase in EIRP (radiation pattern/side lobe, taken
from the VK5HI report)
and DECREASE of distance.
The diff. in calculated sig. level is approx 18 dB (Günther: don't care
about the
picture says dBm... that's because my calc. takes into account the
receiving antenna and receiving system also, just read as relative sign.
strength)
These 18 dB compares very well to the fact, that many commercial
tranceivers have only about 3 dB per S-unit, and 18 divided by 3 is 6
S-units as you also mentioned.

This is the reason for the increase in noise floor.........

vy 73 de OZ4UI / Lars



-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On
Behalf Of Gunther Meisse
Sent: 25. august 2003 03:14
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] Mystery Noise floor on AO-40


I also have observed the noise floor jump up after the passband was shut
down and AO-40 was approaching perigee. Here are the noted facts: Orbit
# 1291 Observation from MA 240 - 252 Noise floor jumped 5-6 S units to
S6 (MB at the time was S9)My traditional noise floor without Passband is
S 0.5-S1.0..
Squint: 92 degrees @ MA251
Noise occupied 160 khz (MB +/- 80khz) ( Based on visual observation of
HP Spectrum Analyzer) Interesting observation: Based on good FEC blocks
the IF matrix showed MB > Leila  / Leila > K-S2 I do not recall that the
MB is normally patched through the Leila??
Other: Magnet system was ON as of course was IHU-2 
INTERESTING.
Gunther
W8GSM

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