Search found 450 matches

by G4GUO
Tue Oct 03, 2017 11:51 am
Forum: DATV - Digital ATV
Topic: Linux based decoding of DVB-S2
Replies: 2
Views: 190

Re: Linux based decoding of DVB-S2

Hi Mike, Yes this project is for the Phase4 Ground station team. I believe Michelle W5NYV is going to demo it at the AMSAT-NA Symposium in Reno, Nevada at the end of the month. They are proposing to use DVB-S2X VL_SNR for future Lunar and Martian Cubesat missions. Being Software Defined means it can...
by G4GUO
Tue Oct 03, 2017 10:32 am
Forum: DATV - Digital ATV
Topic: Linux based decoding of DVB-S2
Replies: 2
Views: 190

Linux based decoding of DVB-S2

I thought I would share my initial work on DVB-S2 decoding in software. It is of little practical use as it requires an expensive NVIDIA graphics card to do the FEC and currently it only operates at <= 333 KS/s. To transmit I was using DATV-Express and to receive ADALM-PLUTO Screenshot from 2017-10-...
by G4GUO
Thu Sep 14, 2017 3:56 pm
Forum: DATV - Digital ATV
Topic: LimeSDR mini
Replies: 2
Views: 261

Re: LimeSDR mini

Yes they seem to be learning by their mistakes.

Hopefully the interface library for all their radios will be the same.

- Charles
by G4GUO
Thu Sep 14, 2017 8:31 am
Forum: DATV - Digital ATV
Topic: LimeSDR mini
Replies: 2
Views: 261

LimeSDR mini

by G4GUO
Tue Sep 12, 2017 3:01 pm
Forum: DATV - Digital ATV
Topic: DATV-Express SSB / FM Radio Transmitter
Replies: 0
Views: 181

DATV-Express SSB / FM Radio Transmitter

Terry G1LPS asked me to make this available. Copy it to a folder and start it up! What is it? It is a simple 70 MHz to 2.4 GHz all band SSB + NBFM radio transmitter for DATV-Express that I wrote 2 years ago. It uses constant envelop SSB. No warranty, no worries! https://www.dropbox.com/s/gze4wc9j0xb...
by G4GUO
Thu Sep 07, 2017 4:47 pm
Forum: DATV - Digital ATV
Topic: Peak to average and QPSK modulation
Replies: 13
Views: 591

Re: Peak to average and QPSK modulation

Good luck with that! Andy G4JNT covers this sort of stuff in his Datacoms column, TAPR published a book on it in 1996 and just about every EE undergraduate communications text book covers it. Amateur Radio is supposed to be about self learning and part of self learning is going out and discovering t...
by G4GUO
Thu Sep 07, 2017 10:48 am
Forum: DATV - Digital ATV
Topic: Peak to average and QPSK modulation
Replies: 13
Views: 591

Re: Peak to average and QPSK modulation

QPSK has a crest factor of 1 and a PAPR of 0 dB if and only if it has infinite bandwidth.
As soon as you start to filter it, that is no longer the case.

- Charles
by G4GUO
Thu Aug 31, 2017 8:22 am
Forum: DATV - Digital ATV
Topic: ADALM-PLUTO (new DATV SDR)
Replies: 64
Views: 4053

Re: ADALM-PLUTO (new DATV SDR)

I have had to re-instate the burst of rubbish the transmitter sends out when changing frequency as that is part of the automatic transmitter calibration routine. At initialisation the unit does a once only baseband calibration then every time the transmitter changes frequency by more than 100 MHz it...
by G4GUO
Wed Aug 30, 2017 8:34 am
Forum: DATV - Digital ATV
Topic: ADALM-PLUTO (new DATV SDR)
Replies: 64
Views: 4053

Re: ADALM-PLUTO (new DATV SDR)

Of course Brian, added. All it has done is show up what looks like an 2.3 KHz FM signal on the transmission. I suspect from PSU noise. I am looking at calibration at the moment. It seems AD's on chip calibration routines don't do very much, certainly as far as getting rid of LO leakage due to IQ DC ...
by G4GUO
Tue Aug 29, 2017 9:17 pm
Forum: DATV - Digital ATV
Topic: ADALM-PLUTO (new DATV SDR)
Replies: 64
Views: 4053

Re: ADALM-PLUTO (new DATV SDR)

Hi Chris, Those problems are both fixed in the next release. I can't release the next release as I am having problems with symbol rates of 4M and above. I have some questions outstanding on the Analog Devices forum to do with sample rates and IQ calibration so not much I can do until those are answe...

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