[amsat-bb] FUNCube-1 (AO-73) Telemetry via FO-29??

[Paul Stoetzer]

Hi Zach,

Yes, I got 9 packets using an Arrow, a FT-817ND, and a High Sierra
Microwave LNAA432 preamp. I did not decode them live, I was using an
Olympus VN-702PC recorder and fed the audio into the Dashboard later. I was
not expecting success, but it did work quite well!

73,

Paul, N8HM

On Fri, Aug 12, 2016 at 10:48 AM, Zach Leffke <zleffke at vt.edu> wrote:

> It is possible to decode, though conditions need to be just so. I was able
> to turn this exact phenomenon into a student project at VT for the
> undergrad SatCom course.  The students had to simulate the event to predict
> when the chain (crosslink) events would occur (line of sight between the
> two birds and FO-29 over the VTGS), what the Link Budget looks like during
> the chain event (so we can predict the best opportunity for successful
> decodes), and what the Doppler profile would look like during the event
> (which tends to be really different than expected, like the center
> frequency drifting UP due to the relative motion between the birds).  We
> then used the VTGS to monitor a few of the events based of the student
> generated schedules and two of the students got extra credit on the project
> because they were present during a successful demodulation (and their
> predictions were spot on!).
>
> I posted a short blurb on our facebook page about it:
> https://www.facebook.com/vtgroundstation/
>
> During that event we were able to dig out 6 packets using GNU Radio and a
> custom AO-73 modem (Basicaly Phil Karn's AO-40 reference code wraped for
> GNU Radio, also implemented by a student).  Probably of more interest to
> this list though is Paul's (N8HM) success with standard equipment.  He dug
> out 9 packets using the Funcube Dashboard and I believe the Funcube dongle.
>
> During that particular conjunction event, one REALLY interesting thing
> that happened is that we caught the instant in time when AO-73 moved out of
> eclipse.  We could see the signal drifting along just a few dB above the
> noise (willing it to increase just a bit to achieve sufficient SNR for a
> solid decode) then all of a sudden it jumped up by 10 dB and packets
> started decoding!
>
> Very cool stuff.  FO-29 is one of my favorite birds for looking at these
> types of exotic cases precisely because it's transponder covers half of the
> Amateur Satellite Service 2m band.  As previously mentioned, lots of
> opportunities for interesting events (crosslinks, gelocating the FM
> interferers, etc.).  AO-73 is also a great bird because of the Forward
> Error Correction on the TLM link (among other reasons).  For our GNU-Radio
> modem, we need about 7 dB SNR (including implementation loss there) for
> solid demodulation.
>
> Fine Business!
>
> -Zach, KJ4QLP
>
> Research Associate
> Ted & Karyn Hume Center for National Security & Technology
> Virginia Polytechnic Institute & State University
> Work Phone: 540-231-4174
> Cell Phone: 540-808-6305
>
>
> On 8/12/2016 4:16 AM, Daniel Estévez wrote:
>
>> El 12/08/16 a las 08:58, Scott escribió:
>>
>>> While monitoring FO-29 for activity tonight, I saw what appeared to be
>>> the
>>> distinctive waveform of the telemetry stream from FUNCube-1.
>>>
>>> Is this common?  Or even possible?  It was certainly a first for me.  I
>>> see
>>> that the telemetry frequency on FUNCube-1 falls inside of the uplink
>>> range
>>> for FO-29.
>>>
>> Hi Scott,
>>
>> Certainly it's FUNCube-1 via FO-29. That's not so common, but I've seen
>> a few reports of this before on the mailing list. Someone even managed
>> to decode the telemetry. Probably you can google if you're interested in
>> previous reports. Also, satellite-to-satellite QSO is also possible for
>> some pairs of satellites and has being done (for AO-7 and FO-29 as far
>> as I can remember). Note that the transponder of FO-29 is quite wide and
>> will retransmit a lot of birds that downlink on 2m, so lots of
>> possibilities for reception via FO-29.
>>
>> 73,
>>
>> Dani.
>>
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>
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