[arm-allstar] simpleusb / channel driver merge status?

[David McGough]

Hi Richard,

If your situation is that the repeater is just randomly generating an
active COS signal when its transmitter is un-keyed, this is most likely an
RF intermod or other interference problem. If you're at a site with
broadcast transmitters, something intermittently arcing (diode noise) is a
likely suspect. Look for (and remove/replace!) any loose, rusted/corroded
hardware near your RX antenna.

If the repeater is getting back into itself so that you hear an audio 
echo, this is most likely severe desense from the repeater's own 
transmitter. Is the problem reduced/eliminated if you turn the transmitter 
power down (temporarily)??

Some antennas and types of feedline are more susceptible to PIM (passive
intermod) generation than others. For example, in general, it's best to
stay away from LMR style coax---any style that has a tinned braid over
aluminum foil (dissimilar metals). While LMR coax may work fine when 
initially installed, after a few years, once a little corrosion has 
started between the braid and foil, it starts causing noise problems. Some 
style of heliax is preferred.

....Your antenna system needs to be virtually "perfect," of course, if 
you're using a duplexer, or your TX will probably interfere with the RX.

Without knowing more about your RF setup, it's hard to do more in depth 
diagnostics??


73, David KB4FXC


On Sun, 1 Oct 2017, Richard Bateman wrote:

> Yeah, I'm using the URIx.  I'm having a couple of issues, but the one
> I'm trying to deal with right now is basically that there is some kind
> of noise that keeps keying up the repeater and we can't figure out
> where it is coming from. It might well just be that it's RF noise and
> we need to track it down, since I hear it when the repeater's squelch
> opens and there is no signal to listen to, but on the spectrum
> analyzer it's not strong enough to come out of the noise.
> 
> Sometimes it'll sit there kerchunking over and over again, multiple
> times per second, despite the PL tone on the receive, and other times
> it's quiet as you could ask for. Putting an extra ground wire as you
> suggest sounds like it'd be worth a try to me =]
> 
> One reason I've been considering trying dsp-based is to find out for
> sure if the issue is in the RF signal or if it's in the CTCSS/COR
> signalling when they shouldn't (for whatever reason, whether the
> radio, which is a TKR-750 version 1, or some electrical issue like a
> ground loop).
> 
> Richard
> 
> On Sun, Oct 1, 2017 at 7:44 PM, David McGough <kb4fxc at inttek.net> wrote:
> >
> > Hi Richard,
> >
> > Are you using a URI or URIx audio adapter?  If so, I've had superior
> > results by adding an extra, heavy-gauge ground lead to the URI. Then, I
> > directly connect this lead to the repeater chassis--a screw on a Kenwood
> > TKR repeaters...This has been my #1 ground-loop solution.
> >
> > Here are a few sample photos:
> >
> > https://hamvoip.org/kenwood-TKR/P1030817.JPG
> > https://hamvoip.org/kenwood-TKR/P1030820.JPG
> >
> > Test TKR-750-2 repeater on bench:
> > https://hamvoip.org/kenwood-TKR/P1030831.JPG
> >
> > ALSO -- on the TKR750/850 repeaters, make sure to notice that the 25-pin
> > accessory plug has separate analog and digital grounds!
> >
> > If you've got RF or other noise issues with simpleusb telemetry, I doubt
> > switching to usbradio DSP-based signaling will fix anything. Try running
> > the TX into a dummy load and test, if possible.
> >
> > 73, David KB4FXC
> >
> >
> > On Sun, 1 Oct 2017, "Richard Bateman via arm-allstar" wrote:
> >
> >> Hi,
> >>
> >> I've been having some issues that I'm starting to suspect might be
> >> related to RF getting into my interface cables triggering my COR and
> >> CTCSS lines (not in any way convinced, but it's on my list of
> >> suspects) and have been toying with the idea of using usbradio instead
> >> of simpleusb for awhile; last time I did that the audio was kinda
> >> crappy, so I switched to simpleusb.
> >>
> >> While looking around I noticed that there is a "TODO" on the hamvoip
> >> page about merging the channel drivers, which I assume might be
> >> something along the lines of using DSP for COR and CTCSS detect but
> >> using the other audio for actual TX?
> >>
> >> Anyway, I'm just wondering what the status of that is and if there is
> >> any way I can help with the efforts; it would help me out a lot on
> >> several different projects.
> >>
> >> Richard
> >> _______________________________________________
> >>
> >> 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 web page - http://hamvoip.org
> >>
> >
>