[amsat-bb] mode S - results - first attempt

Michael Heim kd0ar at sbcglobal.net
Sun Sep 7 19:29:40 PDT 2008

First attempt at hearing mode S.  pass wasnt the best, max elevation about 15 degrees.
receiving using a California Amplifier model 130099.  This is the MMTS unit with the integral yagi with the washer shaped elements.  Yagi boom length about 2 feet, supposedly 16 dBi gain on 2500 MHz.  Modified with the tape over the hairpin tuning, etc....  original crystal, received on 123.2 MHz.  Used an FT-50R for the IF.
Here is what I found:
Unit is linear polarized.  Heard the bird far better using vertical polarization.
There may have been some tropo, as the time of the pass was about an hour after sunset.  Temperature cooled off about 15  degrees in the 2 hours preceeding the pass.
Signal strength ranged from full quieting to "in the noise". with a slow fade to it.
Heard the bird 3 degrees above the northern horizon when there was a peak in propagation.
Beasmwidth is workable, but it is tight enough that I'll need an elevation rotator.  I'm not using one on V/U.
I do not have L band capability (yet), this was just a receiving test, but I do hope to be able to work U/S or V/S if the bird is capable.
Wonder if this is typical for this mode.
Now some quirks regarding my own gear:  The LO is about 150 KHz off frequency, but thats not really a big deal.
I just discovered I had the receiver set to AM.  Here I was slope detecting the thing!  The HT is capable of FM, I was set to AM because I had a brain lapse when I was pre-checking things before the pass.  Then I forgot to change it back for the actual pass.
Trees REALLY kill the signal!  I kinda expected that though.
Looking forward to tersting tomorrow during higher and earlier passes, and of course...using FM to receive!
I have another converter yet to be tried.  The other one has an N connector for connecting to an external antenna.  I see many ops use helicals.  How many turns is considered good for this bird ?

Michael Heim
ARS KD0AR  (EN90rw)

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