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Re: L band Uplink



    Let me add my observations from a recent test of my L-band uplink (L1) when
    AO-40 had 38 degrees of elevation at my QTH (San Jose, CA), was at a range
    of just over 36K miles and the computed squint was 12 degrees.  35W (CW
    mode) into an 18.4dBd antenna (M2 23CM35EZ) with a 1.6:1 SWR  gave me a
    downlink signal that was just over 8dB below the middle beacon as measured
    on my spectrum analyzer.  The same setup on L2 produced a downlink signal
    that was 14dB below the beacon.  The computed EIRP for this setup is
    approximately 4.3KW and I believe that this portion of the AO-40 pass is
    fairly typical of operating conditions, so this doesn't seem to be a QRP
    bird on L-band.

Thank you very much, that's very useful data.  So i bet you were the San
Jose station i was hearing, probably even on the same pass.  Obviously,
i found your signal copyable...  I had no idea you were on the 1.2G side
of things.

I had no idea that L1 and L2 might be 4.4dB different. Indeed, i was 
trying on L2 with perhaps 15 degrees of squint, so maybe i would not
hear myself as well as i might have expected.  Others have reported
making QRP contacts on AO-40, so apparently it's possible, but maybe 
not as easily on L2.  I will be trying tomorrow on L1 with good squint.

I was also able to check my uplink frequency calculation against the
spreadsheet, thanks to some kind gentlemen's suggestion of how to
run it under PPC LINUX.  Indeed, my calculation agreed, but i think 
i was reading the wrong column.  I scanned the whole passband so it
just cost me extra time not knowing if i was looking in the right
place (i was ~10KHz off).

Yes, the frequnecy spreadsheet can be used for other than mode U/S,
just set the transponder LO to the sum of the center frequencies of
the uplink and the downlink.  It was not at all clear to me from the
documentation that this was how to change transponder modes.

			     -- KD6PAG
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