[Ground-station] Need advice on DVB-S2 modem

[Ron Economos]

Sorry, should be 400 Euros.

Ron

On 12/9/19 07:07, Ron Economos via Ground-Station wrote:
>
> I've been using the Digital Devices Max SX8.
>
> https://www.digital-devices.eu/shop/en/tv-cards/tv-cards-for-pcie/340/8-tuner-tv-card-dd-max-sx8-4/8-dvb-s2/dvb-s2x-full-spectrum?c=156
>
> It can go down to 100 kSyms/s and can output raw bbframes. It's also 
> very tolerant to Doppler shift (capable of 30 kHz/s at 10 Msyms/s) . 
> At high bandwidths, you probably won't need LO sweeping.
>
> It's supported in the Linux kernel starting at release 4.20. Plug and 
> play on Ubuntu.
>
> It can also output raw IQ and demodulator IQ. Here's a video showing 
> demodulator IQ.
>
> http://www.w6rz.net/sx8.mp4
>
> It's a little pricey at 500 Euros.
>
> Ron W6RZ
>
> On 12/8/19 17:05, Mike Parker via Ground-Station wrote:
>> A team headed by the University of Arizona is working on a 6-U 
>> satellite that will fly at 500 km altitude.  The satellite, named 
>> CatSat after the UofA wildcat mascot, was described in a paper 
>> presented at the Amsat Annual Meeting.  We are shooting for a launch 
>> that could be as early as one year from now.  The plan is to have a 
>> downlink using DVB-S2 modulation generated by an FPGA on the AstroSDR 
>> card provided by Rincon Research.  This modulation was chosen so that 
>> hams that have been working phase4 ground DVB-S2X might receive and 
>> demodulate the link.  We are planning to transmit a limited number of 
>> ModCod’s.  Modcod 7, QPSK 3/4, and modcod 17, 8-PSK 9/10 are likely 
>> choices.
>>
>> Two experiments plan to use DVB-S2 modulation on the downlink.  One 
>> involves transmitting high quality video, and the other will capture 
>> and retransmit narrowband pieces of the HF ham bands containing WSPR 
>> and FT8 signals.  Closing the link to our 6.1 meter diameter ground 
>> station is no problem, and we are planning on a modulation bandwidth 
>> up to 20 MHz and bit rates over 50 Mbps when using the satellite’s 
>> inflatable directive antenna provided by FreeFall.  But closing the 
>> link to a ham 0.6 meter dish when operating with an onmi-directional 
>> transmit antenna poses a very different problem. We will likely 
>> require small downlink bandwidths on the order of 200 kHz.
>>
>> We are looking for a demodulator to assist in testing the satellite, 
>> and also a demodulator for use in the ground station.  So we are 
>> reaching out to you for suggestions.  We hope that an available 
>> commercially for an affordable price, or perhaps something designed 
>> by a member of this group.  We have neither the desire or time to 
>> reinvent the wheel.
>> Several things concern us we would appreciate advice on.
>> 1) We read with interest a paper by Downey, Evans, and Tollis, 
>> “DVB-S2 Experiment over NASA’s Space Network”.  It said “ typical 
>> commercial DVB-S2 receivers are not designed for symbol rates below 
>> 300 kbaud”.  That is consistent with our observation that many 
>> commercial demodulators do not seem to have a lowest bandwidth 
>> specification.  Anyone know of one that goes lower in bandwidth while 
>> having a high bandwidth capability?
>> 2)  We need to have a demodulator that will output raw DVB-S2 frames, 
>> bypassing any transport layer protocols which are normally used with 
>> DVB-s2 such as Multi-protocol Encapsulation(MPE) or Geeric Stream 
>> Encapsulation (GSE).  Downey, Evans, and Tollis used a Newtec MDM6000 
>> modem.   Is there a better or cheaper solution? (I haven’t priced one 
>> yet).
>> 3) Doppler shifts are also a concern, especially at a low data rate, 
>> but we have a plan to solve that if necessary using a local 
>> oscillator in the ground station that is swept according to ephemeris 
>> predictions to de-Doppler the signal before demodulation.
>>
>> Oh yes, some good news.  The first of our 6.1 meter dishes has been 
>> reassembled in Rincon’s parking lot in Centennial, CO.  A picture 
>> with assembly in progress is attached.  I’m flying up tomorrow with a 
>> 10 GHz feed horn and LNA to see if we can hear signals!
>> Mike Parker, KT7D
>> image001.jpg
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openresearch.institute/pipermail/ground-station-openresearch.institute/attachments/20191209/4e0bc68f/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 61792 bytes
Desc: not available
URL: <http://lists.openresearch.institute/pipermail/ground-station-openresearch.institute/attachments/20191209/4e0bc68f/attachment.jpg>