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

[Paul Stoetzer]

Yep. It's really been dancing around lately.

This seems to be something that surfaces every few months. Interestingly, I
found the last time I noted this drift was around June 1st. I ran pass
predictions and found that passes were occurring right about the same time
then as they are now.

73,

Paul, N8HM

On Mon, Sep 8, 2014 at 2:18 PM, Dave Swanson <dave at druidnetworks.com> wrote:

> 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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>
> _______________________________________________
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