[amsat-bb] FoxTelemetry on AO-91 and AO-92

[Burns Fisher]

Hasan sent me a screen shot of his attempt to collect data from one of the
Fox satellites.  I also showed it to Chris, G0KLA, the author of FoxTelem.
We both agree that the problem is likely to be filtering.  SOMEWHERE in
there is a high pass filter that is not allowing enough of the low
frequencies through.  Another possibility is not FM demodulating a wide
enough bandwidth.  You could try wide FM rather than narrow, or if it is
adjustable, set it to 5KHz.

Chris also says that he expects to be able to decode if the signal is only
a few dB above the noise, so chances are good that a weak signal is not the
problem.

Good luck and 73,

Burns WB1FJ

On Tue, Oct 2, 2018 at 10:57 AM, Burns Fisher <burns at fisher.cc> wrote:

> Let me add just a bit more.  I have a homebrew Lindenblad (circular
> polarity, omni) with an AMSAT wide band preamp out at the antenna, going to
> a FunCube Dongle that is decoded directly by FoxTelem.  I get hundreds of
> packets per day with it.  I have also used an Arrow dual-band J-pole
> mounted at 45 degrees and an AirSpy wide-band preamp with nearly as good
> results.
>
> My experience is that I CAN get decodes without having completely full
> quieting, but it still has to be "pretty good".  I also completely agree
> with Steve that the big trick is to be sure you have no high pass
> filtering.  Best is to use a software defined radio (I've succeeded with
> both HDSDR and SDR# ) with virtual audio cable if you don't have a FunCube
> Dongle.
>
> Good luck!  Let us know how you are doing.  Maybe a screen shot of
> FoxTelem when there is a signal coming would be helpful (although I think
> pictures don't go through on this mailing list).
>
> 73,
>
> Burns WB1FJ
> Fox Flight Software
>
> On Tue, Oct 2, 2018 at 10:46 AM, Stephen E. Belter <seb at wintek.com> wrote:
>
>> Hasan,
>>
>> The answer to your question about the difficulty is yes, and no.
>>
>> There are lots of things that can block the decoding of the DUV.  Get any
>> *one* of them wrong, and it doesn't work.  Get them *all* right, it works
>> great.
>>
>> I am not an expert, but here are a few suggestions.
>>
>> You need a solid, full-quieting signal to decode the packets.  Mark is
>> right; this is much more difficult with an omnidirectional antenna like an
>> eggbeater.  With 80-feet of coax, you probably need a low-noise preamp at
>> the antenna (not in the shack).  When you make a voice QSO, is the signal
>> really full-quieting?
>>
>> The DUV information is very, very low frequency.  You need to be
>> receiving everything from DC to 300 hertz, and passing it to FoxTelem.
>> Typical FM receivers (conventional analog and software defined) filter out
>> the low frequencies so as to not include CTCSS tones which add an annoying
>> rumble or hum to the audio.  So carefully check and adjust or remove any
>> low-frequency filtering.
>>
>> Using a patch cord to connect the speaker output to a sound card input is
>> unlikely to work.  You need to be using a virtual audio cable (software
>> utility that simulates two sound cards connected by a patch cord).  Paul is
>> correct, check the sample rates on the SDRC output, the input and output of
>> your VAC, and the input to FoxTelem.  They should all be identical.
>>
>> Check the levels to make sure nothing is clipping or overloaded:  Windows
>> levels between the HF+ and SDRC, SDRC output, and VAC input and output.
>> I'm using a FUNcube Pro+ dongle and have the Windows level on the FCD set
>> to 9 instead of the default 100.  The best level for your HF+ may be
>> different.
>>
>> I'm sorry you're having trouble.  Maybe these hints and the suggestions
>> of others will help.
>>
>> 73, Steve N9IP
>> --
>> Steve Belter, seb at wintek.com
>>
>>
>>
>> On 10/2/18, 7:56 AM, "AMSAT-BB on behalf of Hasan al-Basri" <
>> amsat-bb-bounces at amsat.org on behalf of hbasri.schiers6 at gmail.com> wrote:
>>
>>     Several of us are having a heck of a time getting any telemetry from
>> the
>>     above birds. DUV just isn't producing anything.
>>
>>     We hear both well enough to make QSOs on the FM transponders, but we
>> can't
>>     seem to get any data thru the decoder.
>>
>>     Is it really that much more difficult to get the TLM via DUV  than to
>>     listen to a voice on the 2m downlink?
>>
>>     Setup:
>>     2m Eggbeater at 7', fed with 80' of 9913
>>     AirSpy HF+ SDR
>>     SDRC V3 Software
>>     FMN 12 kHz (Highpass Filter not checked) and FMW both tried, neither
>>     produce any decoded data.
>>
>>     I am getting telemetry just fine from AO-73, and am also getting
>> perfect Wx
>>     pix on 137.100 with SNR's of > 30 dB.
>>
>>     Am I doing something wrong, or is it just that hard to get FoxTelem
>> to work
>>     with DUV?
>>
>>     Thanks for any help. 73,
>>     N0AN
>>     Hasan
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