[arm-allstar] New Channel Driver Code in Debelopment

[David McGough]

Matt,

Are you talking about a ham FM application or broadcast/commercial FM???  
What kind of repeaters have you got?

An 8KHz sampling rate allows 4KHz of audio bandwidth (the Nyquist limit).  
With HamVoIP running simpleusb, the FIR filters used already provide about
3.5KHz of audio bandwidth, which is fantastic!  Here is the FIR filter
response curve:

https://hamvoip.org/docs/FIR-LP-simpleusb-2018-05-27-1.png

The main factor impacting HamVoIP audio is the CODEC used.  What CODEC are 
you using?  uLAW or slin are best....slin will use a lot of network 
bandwidth, with little extra audio quality, of course.

You should try a radio-less node with HamVoIP.  I think you'll be
surprised by the audio fidelity. Also, note that the audio sampling rate
isn't the FM deviation bandwidth.


73, David K4FXC




On Fri, 29 Apr 2022, M Lech wrote:

> While we're at it, can we implement 16KHz sampling instead of the crummy
> 8KHz sampling ? I'd think I'd died & went to heaven to have the audio
> bandwidth matching our RF links. For me this is huge. The hardware has no
> problem doing it, so why don't we? Thanks in advance!
> 
> 73,
> Matt W6XC
> 
> On Fri, Apr 29, 2022 at 9:27 AM "Dave Petrie via ARM-allstar" <
> arm-allstar at hamvoip.org> wrote:
> 
> > Hi David, just curious if you made any progress with the new channel driver
> > code in development so that chan_simpleusb can send and receive CTCSS like
> > usbradio does. Here is what I found that led me to ask the question.
> >
> > On 9/5/21 11:41 PM, David McGough wrote:
> >
> > Hi Jim,
> >
> > CTCSS generation isn't currently in the chan_simpleusb code. However, it
> > is in new channel driver code in development.
> >
> > All the original usbradio related code and features are in HamVoIP. So,
> > that should work, if you can tolerate the sporadically glitchy sounding
> > audio.
> >
> > How quickly do you need this?  I can probably get you info on the new
> > channel driver in a few days.
> >
> >
> > 73, David KB4FXC
> > _______________________________________________
> >
> > ARM-allstar mailing list
> > ARM-allstar at hamvoip.org
> > http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
> >
> > Visit the BBB and RPi2/3/4 web page - http://hamvoip.org
> >
>