Thanks all for your suggestions on PAPR reduction. Much to ponder there. Mel and Walter - given your years of on-air DV experience, do you have any measuerments/thoughts on average FreeDv Tx power levels?
Thanks, David On 17/6/20 8:38 am, Glen English wrote: > Hi David > > I've been across OFDM PAPR reduction development for many years. > > Most successful simple schemes involve some sort of selective mapping or > bit flipping. > > -IE the PAPR is computed and an alternative trajectory is generated . > > -These can be either tweaking the source bitstream slightly (many methods) > > -and also providing overmapping of the constellation (say 64 QAM points > might only map to 48 unique symbols, giving the system a choice of some > other point that can convey the same data. > > -and also deliberate FEC violation (modify the most encoded code and > remove/reduce the offenders) > > -and also selective bit flipping - easy and fast. > > I would encourage some form of PAPR reduction for any ham OFDM development. > > Without it, OFDM is often and (and ignorantly) overdriven creating > spectrum headaches for adjacent channel users > > > -glen > On 17/06/2020 07:33, David Rowe wrote: >> Hello List, >> >> I've been working with Peter, VK3RV on the surprisingly tricky problem >> of measuring FreeDV Tx power. >> >> Over the weekend I built an inline "sampler" and tried a few averaging >> options to measure the power of a 700D waveform on my spec-an. I am >> using my IC7200 with the drive adjusted so that the ALC just moves. I >> am sampling the power between the IC7200 and my ATU, which is connected >> to a dipole on 40M. > > > _______________________________________________ > 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
