Hi Glen, > it has the least chance of being set up incorrectly and generating > substantial wideband interference.
Plenty of people run FreeDV cleanly. I've seen splatter in a few cases with over driven FreeDV, however on my radio I couldn't make it happen. I guess the ALC was kicking in on the peaks, preventing any clipping and splatter. YMMV. > The reason PAPR reduction is not in the standard specification for DVB > and DRM is that PAPR reduction was very much a 2nd thought, as DVB and > DRM came around the beginning of OFDM in widespread use (apart from DAB) . Well also in DVB/DRM are broadcast modes - there is only 1 Tx for every million receivers, so it's OK to have a single pricey super linear PA, for cheap and reliable operation of the link. Also - multipath is much tougher problem than low SNR. > If I were doing a ham HF-DV mode, I think I would use a a single carrier > with time domain equaliser, and concentrate on minimum SNR operation. I look fwd to your new mode Glen ;) I focussed on low SNR for FreeDV 700D. For example a minimal overhead in pilot symbols, large LDPC codewords + interleaving. However after a few years practical experience - I'm now moving towards better multipath performance, and low latency, even if I lose a few dB in SNR. In some recent HF data tests, the Pactor 4 single carrier modem "was crushed" (the report author's words) on the fading tests (page 7): https://www.winlink.org/sites/default/files/downloads/a_winlink_digital_mode_performance_comparison_based_on_the_ionos_hf_vhf_channel_simulator_-_may_18_2020.pdf I haven't built a single carrier modem with an equaliser for multipath channels (at the sort of SNRs we play with for HF), so not sure what's involved in getting comparable performance to OFDM designs. -/- But I would like to play with some PAPR reduction ideas :-) Cheers, David _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
