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Re: AO40 U-AGC question



Lee KU4OS wrote:

I'm curious what your normal uplink power is.  I typically run just 5w into the antenna.  It appears we were both running 14 dBic antennas so the only difference would be our uplink powers.  I do know that during the weekends prior to FD and even Saturday morning prior to 1800 UTC we were able to make easily copied voice QSOs with 5w.  After 1800 UTC, our signal was barely detectable in SSB and most of the time disappeared entirely.

Wayne replies:

I usually run about 20W to my 436CP30 antenna most of the time for SSB when AO40 is near apogee (not sure the exact amount because I haven't measured the cable loss).  I think this puts me about 6-7 dB lower than the beacon, and it doesn't attract LEILA (I am estimating the difference based on the estimate of 3 dB per S-unit on my FT-847).  I usually am on AO40 when the activity level is fairly high, for instance when there is a well timed window between North America and Europe.  I run less power at the times when the alon is less optimum and the low-squint periods occur at lower altitude.

I'm curious what your downlink antenna is, and what percentage of the stations you contact considered your 5W uplink to be "easily copied".  I'm sure I could get Q5 copy of your signal under ideal conditions, even though your signal is probably 12-13 dB below the beacon under the best of circumstances.  Unfortunately, I rarely have ideal conditions this time of year because of tree obstructions.  I have no doubt that a LOT of AO40 stations won't answer you because they can't hear you well enough to have a pleasant conversation.

Even with my 2-foot dish (patch feed, low noise preamp) I hear stations on AO40 who are significantly more deaf than me.  It's a fact of life on AO40, especially because there is no downlink that penetrates trees.  Some of the "deaf" stations may have GREAT receiving setups, but just have tree obstructions at that time.

Since you are so knowledgeable about the AGC subject, I'm curious what motivated you to operate with 5W during Field Day.  You knew very well that the AGC would be seriously affected.  It's a lot of work to put together a Field Day satellite station.  I wouldn't go to all that trouble to put together a Field Day station that I knew in advance wouldn't be suited to the expected operating conditions.

Wayne Estes W9AE
Mundelein, IL, USA
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