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Orbit 250 apogee



Scott Townley wrote:

16-May-2001 0730Z range>60,000km squint=1.2 degrees
NA/SA/West+Cent EU/West AF in view
An *excellent* RX system test with such a low squint!  If you can spare the
sleep, see whatcha really got!  (And let us know)


Wayne replies:

I was up for the orbit 250 apogee and made 5 contacts.  This was my first
time to listen to AO40 near apogee.  I was impressed that the beacon was 3
S-units above my noise level with relatively little fading.  That's with a
21 dBi 60 cm TranSystem linear dish and AIDC3733 downconverter (stub cut,
thermistor added).  I was disappointed that there weren't more stations on.

It was also my first experience with LEILA.  That thing is really picky.
Here are my observations about LEILA:

1. With my (less than optimum) receiving setup LEILA likes to make the siren
tone just when I can start to hear my downlink well.  I can't run more than
about 10W (after cable loss) into a 30 element CP yagi without getting the
attention of LEILA.

2. For a few minutes before I shut down the radio I was doing other things
while still tuned to the frequency of my last QSO.  There were no stations
on that frequency, but the LEILA siren came on several times.  Did anybody
else hear the LEILA siren on an empty channel?

3. It appears that people uplinking on 23cm can get MUCH stronger downlinks
(than people uplinking on 70 cm) without triggering the LEILA siren tone.
I'm not sure it's reasonable for LEILA to completely eliminate AGC on the
70cm uplink because that doesn't permit decent downlink signal strength.

I don't know how much better I will hear when I finally get a 2155 MHz stub
or ISM ceramic filter to eliminate noise from the 2155 MHz image in my
TranSystem downconverter.  I'm still disappointed in the downlink signal
strength of AO40.  For me, the AO40 downlink is less readable than what I
got from AO13 with much less RX antenna gain.  Part of my readability
problem is that for AO13 I used a Timewave DSP-9+ noise reduction unit which
greatly improved the readability of weak signals.  The DSP noise reduction
in my FT-847 doesn't seem to improve readability at all.

I asked this question a week ago and didn't get an answer:  Will the "final"
S-band downlink use more power and/or a higher-gain antenna?

Wayne Estes W9AE
Mundelein, IL, USA

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