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AO-40 S2 reception with the Drake converter



Good Morning to ALL

For those interested I was able to received the S2 beacon this morning on
my first attempt thanks to a good squint angle.  My setup here is the
Drake converter with the two IF coils and capacitors removed.  No other
mods have been made and I do not have a pre amp.  I was using a home
built IF down converter to convert 2400.0 mhz to 28.0 mhz and into a
Yaesu FT-840.  This morning I used a recently completed W0OQC design 20
turn helix.  Mine turned out to have 21 turns (I never could count very
well).  I had the antenna and down converter mounted on a piece of PVC
clamped in a Workmate  (or Shopmate or whatever you call those portable
work stands) in the driveway.  The down converter was hooked to the power
inserter and the IF converter in the garage where the rest of my rigs are
located with 100 feet of RG-6.  My location is Chesapeake, VA - FM16.

I acquired the beacon at 1205Z.  IT 1.5  indicated an elevation at 4
degrees and the squint angle of 7 degrees.  The signal was clearly above
the noise.  I probably would have acquired it closer to horizon break but
I did not have the beacon frequency set up in IT and I mistakenly thought
the range was closing so I was looking above 2401.300.  As soon I
realized my mistake and tuned down below 2401.300  I heard the signal
easily.  Signal was weak but readable with some fading.  I don't think it
ever got much more than about 6 or 8 db out of the noise but that was
strong enough for me to aim the antenna by hand by listening to the
receiver 25 feet away.  I copied the signal until I terminated my test at
1330Z.  The neighbors were beginning to stir and the XYL was afraid one
of them would call the guys who provide those funny white coats with no
holes in the sleeves!  I guess it might be a pretty unsettling sight to
wake up Sunday morning and see some fool bundled up in a heavy coat with
something that looks like a Star Wars ray gun aimed at the sky!

When I terminated the test at 1330z the signal was just above the noise
and IT indicated a squint angle of 55 degrees.  The signal never did get
very strong but it was strong enough to work CW during the entire period
and it was strong enough to work SSB for much of the time.  I have
concluded that I really do need a pre-amp though.  Either that or perhaps
do some of the mods to the front end of the Drake converter.  Bill's
antenna design seemed to perform OK and the beam pattern seemed sharp but
I did not have anything to compare it with.  As some of you no doubt
know, Bill's design uses a shorted loop to feed the helix.  You can find
info on it on the web site of N0ZHE.  I had no way to optimize the match
so I just tried to duplicate Bill's dimensions the best I could.  I plan
to build a similar helix with a conventional feed in the next week or so
and compare the two.   I also want to build the signal source/antenna
bridge that was described in the AMSAT Journal a few months ago so I can
adjust the match of the antennas correctly.  This is a great opportunity
to do some antenna experiments with AO-40 operating in this mode.

One other thing that seemed strange to me this morning was that I was
able to decode (or partially decode) some telemetry frames with the
AMSAT-France program even though I did not get around to trying this
until after the squint angle was above 40 degrees and the signal had
dropped off some.  The signal to noise ratio as indicated by the spectrum
display was good, the programmed locked up almost immediately and the
frame was displayed quickly.  There was some garble in the header info
but it looked like the rest of the frame was solid.  I wondered if the
garble was in the message or in the decoding.  At any rate I could never
decode the telemetry on 2M with signals as weak as I was receiving this
morning.  I'm not at all sure what that means.

Sorry for the bandwidth.  My brief summary got a bit long but I know
there are a number of people who have not received AO-40 with the Drake
converter yet so I hope this information will be helpful to them.

73 de Jess - W4MVB

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