Has a module for Allstar been considered? I have here a RPi4B loaded with ARM-Allstar loaded and on it compiled the Codec2-dev library, for a start.
Thanks Glen on the radio info. True in the Philips/Simoco PRM80 radios, there's a balance pot, Ref Xtal and PLL VCO. Possible repeater here, a Tait T800 2m, ready to go. Alan VK2ZIW On Sat, 18 Apr 2020 19:58:35 +1000, glen english wrote > Most FM radios with integer PLLs will have a loop filter bandwidth > of maybe 150 Hz, - enough to deal with most microphonics. > > In order to modulate below about 250Hz, LF audio, like subaudible > tones , are injected into the reference oscillator- the PLL will > follow that because it is within the loop bandwidth. The voiceband > audio is split with HP and LP filter. ABove 250 Hz goes to the > varactor modulator on the VCO, and below 250 Hz goes to the > reference frequency modulator. > > Modern 2 way radios have fractional divider PLLs and loop > bandwidths of maybe 60 kHz. If applied to the varactor VCO modulator, > the modulation would be corrected- these radios use IQ modulators > to directly modulate the (clean) carrier frequency produced by the > fractional PLL. > > So: for the majority of FM gear, do not bank on any decent > fidelity below about 300Hz. Your mileage may vary- it will depend > exactly where the loop bandwidth was set. > > The newer 2 way PMR radios, like Tait TM8000 etc, they offer > external FM down to DC modulation on their external IO connectors, - > they have an IQ modulator and the sky is the limit > > -glen > > On 12/04/2020 4:47 am, Steve wrote: > > oops, I keep typing Symbols instead of Samples > > > > /* Slow Data + Voice Bits + Sync Bits = 747 Bits = 5976 Samples */ > > /* Full Data + Sync Bits = 747 Bits = 5976 Samples */ > > > > Without the bit-stuffing the spectrum cleaned up and it actually > > sounds more random, but this is just a function of your test program, > > as long runs of 1's would make a mess without scrambling. I think most > > FM direct modulators have a filter for below 100 Hz. > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 --------------------------------------------------- Alan Beard OpenWebMail 2.53 _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
