[amsat-bb] SO-50 & frequency stability as of late

[Dave Swanson]

Twice during the 1655Z pass just now I actually had to shift UP in 
frequency to hold the downlink. Right at AOS I picked up the signal at 
.795, made a contact, and about 30 seconds later I heard a very 
noticeable 'shift' in the noise where it was basically unreadable. I 
shifted down, it got worse, so I went up and picked it back up at .800 
clear as a bell. About 6 minutes later, near my apex, I had followed the 
doppler down normally to about .780, and it jumped back up again by 
about another 5 or so. Each time it did this, it was in the middle of 
someone else's transmission and there was an abrupt 'shift' that didn't 
sound anything like the gradual worsening that I normally hear with 
doppler.

Just my observations from a sat-noob. Also first post on amsat-bb... o/

73, Dave, KG5CCI

On 9/8/2014 11:30 AM, Alan wrote:
> Clayton,
>
> I have been watching it shift 5-10 KHz or so on some passes, though 
> 3-5 KHz is more common.  Watching
> it with a DSP rig allows you to compensate.
>
> The more interesting question is what, if anything, the uplink is 
> doing?  I got up for a 0200 L pass
> to experiment, and there was nobody else on.  I thought I had it 
> figured out, and suddenly the
> downlink shifted.  Then, my uplink data seemed wrong, as if it also 
> shifted.   ;(  Will try again the
> next time I have some insomnia.
>
> 73s,
>
> Alan
>
> WA4SCA
>
>
> <-----Original Message-----
> <From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] 
> On Behalf Of Clayton Coleman
> <Sent: Monday, September 08, 2014 10:54 AM
> <To: AMSAT-BB
> <Subject: [amsat-bb] SO-50 & frequency stability as of late
> <
> <I have been noticing some irregular shifts in SO-50's downlink
> <frequency the past several days.  I noticed it in the past but it's
> <been a while since this occurred.  Several others are reporting it as
> <well.
> <
> <At my AOS today (15:12 UTC, orbit # 62976), SatPC32 had predicted the
> <downlink to be near 436.801 MHz, when in fact I was receiving the bird
> <at 436.793.  It proceeded to jump up to 436.795 at my TCA before
> <making it's way down to 436.780 near my LOS.
> <
> <This seems to be posing some issues for people using full computer
> <control and also those who stick to pre-programmed memory channels to
> <make frequency adjustments during a pass.
> <
> <Considering this recent frequency instability, I would recommend you
> <manually tune for the strongest downlink frequency.  This would help
> <eliminate some issues with stepping on stations engaged in existing
> <QSO's.  An alternative would be to try using RIT if you insist on
> <computer control.
> <
> <The old rule applies -- if you can't hear, don't transmit.
> <
> <73
> <Clayton
> <W5PFG
> <_______________________________________________
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