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AO40 V-band uplink observations

A rough mental calculation suggests that the AO40 V-band uplink should require LESS power than the U-band uplink.  The AO40 V-band antenna has less gain than the U-band antenna, but the 9 dB reduction in path loss should more than compensate for the difference in antenna gain.  The actual V-band uplink performance seems to be about 8 dB "deafer" than the U-band uplink.  My 500W EiRP V-band uplink was right at the noise level on the downlink.  On U-band I can get about 8 dB above the noise level with the same EiRP.

I was pleased to note that there was no desense to my 123.4 MHz IF when transmitting on 148.9 MHz.  The antennas are about 1.5m apart.  Before the test I disconnected the downconverter IF coax from the coaxial relay that normally switches between the 2m yagi and the downconverter.  I figured the coax relay might not have enough isolation to minimize desense.  I also had to disconnect the power wire to the coaxial relay and unplug the "2m TX inhibit" cable.  Normally, a single switch powers up the downconverter, latches the coaxial relay, and inhibits 2m TX.  Those functions needed to be temporarily separated for the V/S2 test.

Wayne Estes W9AE
Mundelein, IL, USA
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