Thanks David for the news. One question: how high can the Pi transmitter go in frequency? Our 70 cm band is pretty crowded, but the 23 cm band and 2305-2400 MHz bands are underutilized and we want to make use of them. The Pi/RTL system is a good candidate because of price.
Adrian On August 9, 2020 8:14:52 AM UTC, David Rowe <da...@rowetel.com> wrote: >Hi Adrian, > >You data mode (and HNAP) sound pretty cool. Thanks, I enjoyed the SDRA >HNAP talk by Lukas, that's quite a sophisticated system. > >-/- > >A couple of recent developments in this area by Bill, VK5DSP, and >myself: > >1/ We have ported the 4FSK/LLR/LDPC code work to C in this PR > > https://github.com/drowe67/codec2/pull/136 > >Some command line examples down the bottom, e.g. 5 bits/s with a MDS of >-160dBm (!), and 100 bit/s across-town links on 25uW (!!): > > http://www.rowetel.com/?p=7273 > >You can scale to any bit rate you like of course, if you have the link >margin. > >The 4FSK/LLR/OFDM work has been carefully developed to hit the >theoretical rate limits, which I understand are about Eb/No=7dB >(information bits) for 4FSK. Pls correct me if I'm not explaining this >correctly Bill! > >2/ The RPi/RTLSDR based system is moving along, yesterday we managed to >sent a few packets over a 10km non-LOS (135dBm loss) link on 145.5 MHz >at 5000 bits/s, using 13dBm Tx power. Current code/status here: > > https://github.com/drowe67/pirip > >3/ Steve and I have also been work on the HF data modes. We have >initial versions of 3 new OFDM/LDPC data modes running in C, between 10 >and -5dB SNR. Next step is some tuning and QAM16. That modem might >also run OK at higher rates on VHF and above, but we haven't tried it. > >Cheers, >David > > > >On 9/8/20 3:57 pm, Adrian Musceac wrote: >> Hi David, >> >> I've watched with interest your recent foray into FreeDV data >transmission. >> There's a new and interesting project called HNAP (https://hnap.de ) >> which has the same goals (long distance IP links). The project is >well >> described in this year's SDRA talk by Lukas O. >> Inspired by both your project and theirs, I wrote a 4FSK data mode >which >> has the following characteristics: >> >> - 100 kbaud, 1/2 convolutional code >> - fits in a 200 kHz channel on the 70 cm and 23 cm bands (IARU region >1 >> allocations) >> - full duplex >> - works with 50 watt FM amplifiers >> - good SNR performance, 20 km point to point access distance tested >with >> small non-directional antennas >> - carries layer 2 (Ethernet) frames >> >> Do you have anything planned for VHF as well? >> >> Best regards, >> Adrian >> >> >> _______________________________________________ >> Freetel-codec2 mailing list >> Freetel-codec2@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> > > >_______________________________________________ >Freetel-codec2 mailing list >Freetel-codec2@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/freetel-codec2
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