Re: [Freetel-codec2] why 4, and fsk, psk redux

Thanks Glen for taking the time to explain that in such detail, it's useful to have it posted to a mailing list as a google-able future reference. I've attached a simple summary in PNG form, extracted from this presentation: http://www.rowetel.com/?p=4279 Cheers, David On 08/10/17

Re: [Freetel-codec2] why 4, and fsk, psk redux

Maybe I need to summarize a bit, and remove the ambiguities of the argument, as I think what I wrote had a few too many assumptions of argument. and I made a few mistakes , I was a little tired when I wrote , mixing coherent/incoherent spacings etc..(I don't run simulations, I just do the math) .

Re: [Freetel-codec2] why 4, and fsk, psk

seems I replied to David and not the group yesterday re sent! Hi David Firstly I will clarify, my reference of poorer mobile channel performance for 4FSK compared with 2FSK pertains to incoherent, non linear discriminator detection . (4FSK is better than 2FSK for linear orthogonal -agreed)

Re: [Freetel-codec2] why 4, and fsk, psk

On 10/6/17, glen english wrote: > Considering we are not bandwidth constrained, why is everyone so > enamoured with 4 level waveforms like 4FSK , When two level/ two state > waveforms like BPSK and 2FSK are far more robust in a mobile environment > > Hi Glen, I'll

Re: [Freetel-codec2] why 4, and fsk, psk

If implemented correctly, 4FSK gets you 3dB over 2FSK on an AWGN channel. The FSKs can use class C PAs. For DRM/C4FSK they _are_ bandwidth constrained due to the high bit rate of AMBE/standards (which is black box with a bit rate so they have no choice over). I presume this is the reason for

Re: [Freetel-codec2] why 4, and fsk, psk

There was some neat AM designs a couple of years ago, but I think they all petered out last year. Narrow-band FM still remains king on VHF and up. I play around a little bit with an used FT-857d, but that's a Cadillac radio, and I use it mostly on HF. I think that's the problem with the current