Re: [Freetel-codec2] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

Hi Adrian Help me understand why the need to use 4FSK compared to say FSK OR BPSK ? For voice at 700bps there are few bandwidth issues for amateurs... The multi level modulation (4FSK) will be inferior to others (without an time delay equaliser) when the long delay multipath is severe The

Re: [Freetel-codec2] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

There are some improvements that could be made (while using legacy FM demodulators). A common mistake is to tightly band limit the input the the modem. The problem with this is that the FM clicks- spikes spread out and cover perhaps several bits of information . The clicks have to be removed

Re: [Freetel-codec2] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

Hi Glen, We don't need to use the same chain for digital demodulation, since we are not software constrained. Using Gnuradio, we can simply reuse a flowgraph and connect/disconnect blocks on a click of a button to switch from one mode to another. What I don't want to do, is write a custom

Re: [Freetel-codec2] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

Ham modes/implementations that are not bandwidth critical should always do better than bandwidth constrained modes like DMR. consider the low deviation that DMR operates with... a symbol rate of 4800 sps and a maximum deviation of 1944 Hz, This is a comparatively low modulation index. This low

Re: [Freetel-codec2] [Discuss-gnuradio] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

On 9/12/17, Phil Frost wrote: > I did some experimentation with this technique on BPSK31, and I was able to > get a little more performance in simulations with a matched filter and > trellis decoding than fldigi and PSKCore got with their unmatched filters > designed to

Re: [Freetel-codec2] Why the DMR 4FSK modem is less optimal than David Rowe's 4FSK modem

On 9/12/17, David Rowe wrote: > > Have you performed any BER tests to conform the BER versus Eb/No > performance of the DMR waveform over ideal FSK? > > Cheers, > > David > Hi David, No I haven't done any BER tests yet. The code for BER is partly in place, but the 4FSK