Thanks Gerhard, You have some nice toys :-)
I am also seeing a PAPR in the range of 8.5dB (75/10). This is curious as when I measure the PAPR of the DSP signals in software, I get around 13dB. Might have to revisit my sums, or how I measure peak/peak envelope power. 800XA uses FSK, basically a sine wave, so PAPR should be around 3dB. It's interesting how the waveforms (apart from 1600) are about the same, 2020 has 31 carriers, 700C/700D about 18. We must be lucky to have some of the phases add up the right way so the peaks aren't too high. Cheers, David On 18/6/20 5:41 pm, [email protected] wrote: > Hello All, > > What I can contribute to this discussion is: > > - For FreeDV operation on HF I am using normally 100 - 200 W average > power. My PA is a 2,5 kW SSB type. > > - I have now measured the average and peak powers using my WaveNode WN2 > and KF-8KW RF Sensor, but just using my transceiver, so without the PA: > > mode avg (W) peak (W) PAPR (dB) > 1600 1.5 20.8 11,4 > 2020 1.9 13.4 8,5 > 700C 1.7 12.9 8,8 > 700D 1.6 12.2 8,8 > 800XA 7.2 10.4 1,6 > > > > Maybe that helps. > > 73's > > Gerhard OE3GBB > > > Am 18.06.2020 09:40, schrieb David Rowe: > >> Hi Take, >> >> On HF channels OFDM is a neat solution to multipath problems like delay >> spread and frequency selective fading. Single carrier modems are >> possible but require a different design, in particular an equaliser to >> handle the channel. >> >> As Hams tend to have SSB radios, they are already designed for waveforms >> (like analog SSB) that already have significant PAPR. So OFDM is >> reasonable fit to available hardware, despite the PAPR issues. >> >> Cheers, >> David >> >> On 18/6/20 10:20 am, Tsutsumi Takehiko wrote: >>> Hi Glen, >>> >>> >>> >>> What is your position of Single-carrier FDMA or LP-OFDMA technology >>> compare to PARP reduction scheme which you have rich experience in your >>> memo? >>> >>> >>> >>> I wonder why radio amateur society leaves PARP issue untouched when they >>> adopt OFDM technology. >>> >>> >>> >>> Does it comes from SSB experience which has about 5dB PARP? >>> >>> >>> >>> Regards, >>> >>> >>> >>> take >>> >>> >>> >>> de JA5AEA >>> >>> >>> >>> Windows 10 版のメール <https://go.microsoft.com/fwlink/?LinkId=550986>か >>> ら送信 >>> >>> >>> >>> *差出人: *Glen English <mailto:[email protected] >>> <mailto:[email protected]>> >>> *送信日時: *Wednesday, June 17, 2020 8:09 AM >>> *宛先: *[email protected] >>> <mailto:*[email protected]> >>> <mailto:[email protected] >>> <mailto:[email protected]>> >>> *件名: *Re: [Freetel-codec2] FreeDV Tx power >>> >>> >>> >>> 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] >>> <mailto:[email protected]> >>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >>> >> >> >> _______________________________________________ >> Freetel-codec2 mailing list >> [email protected] >> <mailto:[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
