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S2 Received strong in Iowa 1345Z 3 Jan 01



I must of finally fixed the old DEM Mode-S downconverter.  The suggestion of 
adding a small inductance in parallel with the 94 MHz
XTAL, helped me net the osc to freq better, and the unit was MUCH
more stable.  My unit has the RSK-1's replaced with MPS5179's which
helped a lot, a 60*K PTC thermistor soldered to the xtal and now a
0.33 uf molded choke across the 94 MHz Xtal.  All three mods seemed
to help.

The S2 beacon translated to 145.303 MHz on my unit, with doppler and
the slight error in the LO at AOS-- nearly as predicted.

With the PVC (sorry K9EK) 33-turn RHCP helix, early in the pass (AOS + 5 
mins or so) the sat peaked at S-7 on the receiver (Kenwood R-2000 with VHF 
converter) and averages S-3 to S-5.  Later when the sat started to fade, I 
tried a four turn LHCP helix, and a Hughes 18" DSS dish I had, and the 
signals seemed stronger on the dish than on the
helix.  I'll have to work out the numbers to see if I'm insane or
not, but it sure seemed that way.  I think I'll need more turns
on the feed helix for proper illumination, but I was suprised to hear
what I did with the four turn.  BOTTOM LINE:  18" DSS dishes will work.  Was 
still hearing sigs when I quit at about MA 30 (had to go to work :( ).

This was completely armstronged (no tripod for either antenna, and I held 
the 4-turn helix to the feed) so it was a very clumsy operation-- stuck the 
antenna out the patio door off the kitchen.  XYL was still in bed (thank 
god)... made me a little late for work...was worth it.

The other interesting point is during some deep fades, I took the
4-turn LHCP helix feed, and was able to hear the sat with it better than 
with the RCHP helix or the RHCP dish.  Has anyone else noticed
better sigs with LHCP at the higher squints?

Fred W0FMS

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