I believe it is just direct FSK of the FM oscillator. +/- some deviation. Using the data port of most modern VHF radios. So on receive you just slice the ratio detector (discriminator output).
The bit-stuffing keeps from long runs of a high or low. My experiment is to replace bit stuffing with a scrambler, but I haven't found all the places to remove the bit-stuffing :-) On Tue, Apr 7, 2020 at 4:08 PM David Rowe <[email protected]> wrote: > Hi Steve, > > From what I understand (please feel free to correct me Jeroen) this is a > baseband PAM waveform over analog FM. I'm haven't seen any theoretical > analysis of these schemes, but we did measure some a few years back: > > http://www.rowetel.com/wordpress/?p=4663 > > Cheers, > David > > On 7/4/20 5:58 pm, Steve wrote: > > What would be expected here? Say about 9.5 dB Eb/N0 at 10E-5? I think > > that's what the G3RUH modem got. > > > > It will definitely fill up the channel! :-) > > > > On Tue, Apr 7, 2020 at 2:43 AM David Rowe <[email protected] > > <mailto:[email protected]>> wrote: > > > > Steve and Jeroen - it would be interesting to measure the modem BER > (or > > Packet Error Rate) performance. Steve - we could use cohpsk_ch to > > inject measured amounts of noise. > > > > Cheers, > > David > >
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