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Re: AO40 U-AGC question



> 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).

Those numbers sound about right.  Considering that the vast majority of the
time the AGC is in the 6-9 db range, your 500w EIRP uplink would put you in
the MB-6/7 dB range as you said.  Even this is 3-4 dB stronger than
recommended.

> I'm curious what your downlink antenna is

I'm using a 3 foot offset dish with a measured total system Noise Figure of
0.9 dB.

>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.

You're almost exactly right.  My signal is generally about that level with
"usual" 6 dB of AGC.  If the AGC were running almost zero, I would probably
need to back down just a bit.  The critical point is that the MB-10 dB point
represents an 18 dB SNR which is very easy to copy.

> 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.

You nailed that one Wayne and I very nearly chose not to.  The deciding
factor was that my local Club operates FD in the QRP/Battery/Solar category.
Since I wanted to participate with the Club, I was limited to 5w Tx output.
As it was I'm glad I did.  Lot's of members were quite impressed with
hearing all the QSOs and the long passes.  Knowing that it was likely that
we'd see a repeat of FD '02 we were prepared and operated CW for the full
weekend.

Next year we're hoping to have 5w on L-band and a larger dish to use for
uplink which should allow SSB QSOs as well.  I think we're missing a great
chance to show off AO-40's capabilities by making it much harder than it has
to be.  Imagine the impact it could have if the non-satellite ops in a club
could see us easily making QSOs with a 2-3 foot dish and a small 2-3 foot
yagi on 70cm without having to haul out the big amps or power supplies.

If we want to build our membership we need to be showing off our satellites
in the best possible light.

73,
Lee-KU4OS

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