Re: [amsat-bb] Why V/S in stead of U/S

["Greg D." <ko6th_greg@xxxxxxxxxxx>]

Hi Jeff,

Yes, sort of.  I did the mods, but with a different choice of crystal 
frequency.  The modification consisted of replacing the crystal, adjusting 
the one capacitor in the PLL circuit, and adjusting the trimmer to tune it 
to the right frequency.  Another ham helped with the last two steps, as the 
capacitor change involves SMT rework that is a little touchy, and he has the 
test equipment to get the frequency really close.  The diode-and-resistor 
trick for a signal generator works surprisingly well, so you really don't 
need the test equipment.  And if the PLL doesn't run, tweek the position of 
the cap ever so slightly.

I am lucky & cursed to have an Icom R7000 all-mode scanner.  Prior to 
AO-40's launch there was a lot of uncertainty which uplink would be used 
with the S-band downlinks, so I opted to modify my Drake for an IF frequency 
of 2100 mhz (xtal at 8203.125 mhz).  That puts the 2401 mhz satellite band 
within the 2880's unmodified IF at 301 mhz, which is comfortably away from 
both V & U bands, works with the R7000, and gives me the lucky option to 
work either mode.  It also makes the math easy for figuring where the bird 
should be.

Of course, I'm cursed because the R7000 is pretty deaf, compared to most 
modern ham rigs.  I spent my AO-40 years at S-zero on the meter.  Still lots 
of fun, and I gained experience in making better antennas :-).

If you're interested, pictures at http://home.jps.net/~gregd/hamsite.htm

Good luck,

Greg  KO6TH


Has anyone actually done the 430 MHz mod to the 2880 Drake described here...

http://www.ne.jp/asahi/m-arai/gkz/sband/mod32e.htm

73 Jeff kb2m
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