Hi Adrian, The RpiTx doc suggest 1.5GHz, but I haven't tried it. Suspect it gets "noisier" as freq increases, however as the power is so low it may still meet spurious requirements.
Cheers, David On 9/8/20 6:48 pm, Adrian Musceac wrote: > 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 <[email protected]> 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > ------------------------------------------------------------------------ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
