On Wed, 2021-08-25 at 07:20 +1000, glen english LIST wrote: > WRT the pilot levels, - other OFDM HF modes use 3dB. That David's > skill and best practice.
Absolutely, I asked about this because it's an area of the art that I have little knowledge of, HF has been a diminishing part of RF design I have been aware of in many ways. I'm delighted that there is open documented work in this area. > Have a look at the specification for another HF OFDM mode like DRM. > many respects, David's implementation is excellent for a pilot boost > of only 1dB- very impressive. OK, I know next to nothing about DRM so any other references would be welcome. > > I think the opinion from your QAM friends may illustrate they are > il-informed about HF OFDM techniques. Yes, I've been talking about WiFi and LTE cellular modulation, where there is a big difference in requirements. David did tell me that the error rates are a huge way apart, I tend to think in 1:100,000 BER due to conditioning from many years working at low reference error rates. I don't do the modem design, but I have been heavily involved with keeping the Tx distortion levels low to avoid perturbing up to 256-QAM. A very different environment. > > Download ETSI ES 201 980 and take a look, section 8.4 pilot cells. > 3dB and walking pilots are used . DRM is in general transmitted up to > 20kHz bandwidth and more pilots are required. > > In DVBT- same power is used but the pilot data is repeated and the > demod averages over multiple periods. It just goes to show that 40+ years in RF engineering and a whole load of different systems work does not give us encyclopaedic knowledge of everything that's out there. Thanks for the reminder and the additional information. -- Brian G8SEZ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
