[amsat-bb] Trying to find my downlink

Bob WB4SON at gmail.com
Mon Jul 18 17:55:13 UTC 2016

First off, I'd suggest using CW to find downlink.  It is much easier to
find that than a weak voice signal.  Do as Bernhard suggests and set your
RX to the middle of the downlink passband, then adjust your TX until you
find yourself.

FO-29 and the three XWs have fairly predictable input/output offfsets, so
once you figure it out, you only need to adjust for doppler.

AO-73 is an entirely different thing -- the uplink frequency for AO-73 is
about 10-15 KHz HIGHER than the published values as the uplink frequency
varies with spacecraft temperature, so what works on one orbit might not
work on another, but again, it will get you close (you'll be tuning your
uplink +/- 2 KHz to find yourself).

FO-29 is your best bet to begin.  VERY sensitive receiver, longer orbit
window, stable, etc.

Once you figure out your offset, MacDoppler should do a good job for
everything but AO-73, and Funcube2.

73, Bob, WB4SON

On Mon, Jul 18, 2016 at 1:34 PM, B J <va6bmj at gmail.com> wrote:

> On 7/18/16, Philip Chimento <vze275m9 at verizon.net> wrote:
> > I have an IC-9100 using MacDoppler and hooked up to two home-brew
> Eggbeater
> > II antennas. I have had a lot of trouble finding my downlink on pretty
> much
> > all of the SSB satellites that I have tried; AO-7, FO-29, AO-73 and the
> XWs
> > (2A, 2C and 2F). Does anyone have suggestions, strategies for finding the
> > downlink (so I don’t wind up annoying everyone else by uselessly
> > transmitting).
> <snip>
> I've got the same problem.  I first set my software (in my case,
> Gpredict on Linux) to mid-band.  If there isn't anyone on frequency, I
> start looking for my downlink.  If there is someone, though, I move
> further up in the band so that I'm out of the way and won't cause any
> interference.
> I keep the uplink frequency steady and adjust my downlink.  For me,
> the trick is finding what the offset from the nominal value is.  On a
> new satellite, I start there and move up (or down, whichever the case
> may be) slowly.  On ones I've been on before, I start at the
> approximate offset.
> I simply speak into my mike and announce who I am and the purpose for
> my transmission until I find my signal.  I usually find it in a minute
> or two.
> I have to do it that way as I need to set up my station outside and I
> have only two hands.  I hold my antenna with one and my PTT switch
> with the other, keeping a finger or two free so that I can adjust my
> software setting.  Operating a Morse key might be a touch difficult
> when my hands are already full.
> This has worked for me so far and I haven't yet figured out a way to
> make it quicker or easier.
> 73s
> Bernhard VA6BMJ @ DO33FL
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