[amsat-bb] Re: AO-51 mode L uplink
Alan P. Biddle
APBIDDLE at UNITED.NET
Tue Jun 19 00:07:17 PDT 2007
After rechecking the exact LO frequency of my TX converter and adjusting the
DOPPLER.SQF file, I found I was pretty much on frequency last night. I am
still doing some empirical testing, by slowly turning down the power, and
tweaking the TX frequency in 1 KHz increments while talking. That has
greatly reduced the dropout times compared with some other stations. Right
now, it looks as if being slightly higher than the nominal uplink, 2-3 KHz,
works better for me. Of course, that depends on how well everything in your
station is calibrated.
Initially, try jumps of 5 KHz, up and down. If you are nearly centered, it
won't make much difference. However, if you are significantly off frequency
but still in the passband, one of those jumps will take you out entirely,
and the other will make a great improvement. That is what I found. Once
you find the right direction to go, try another 5 KHz. If it deteriorates,
go back, and fiddle with smaller steps.
Also, as VE3NPC commented, the downlink may be slightly higher. I receive
435.300 with the discriminator centered, but I find this downlink looks
better at 435.1515. No question you have to hit the bird a bit harder for a
full quieting signal. Lots of fun, though.
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