[App_rpt-users] Squelch issue with RTCM and Kenwood

James Cizek james.m.cizek at gmail.com
Mon May 1 11:04:27 EDT 2017


Hi folks,

After dozens of trips to the mountains to get all the physical
infrastructure upgraded and changed out to Allstar/RTCM, I am finally
getting back to some little cleanup items.

I've written before on the "squelch crash" issue, and found that once
things were tuned up, no one really had any issues with it.  We are having
severe issues with it and I am trying to narrow it down.

All sites consist of:
Kenwood TKR750 (or 850 if UHF) repeater.
RTCM
Local on-site PC (micro itx PC with Intel Atom D2500 1.8Ghz Dual core CPU
and 2GB ram)
Local mikrotik router (RB2011 in most cases, some CRS125)  Except for
voters, all repeaters are using the DIAL box plugged into the same local
router as the RTCMs (ie, just about zero network latency)

Some sites have 1 repeater, some 2, the biggest site has 2 repeaters and 2
voters.
Squelch and Diode calibration was done per RTCM manual
RX level set per manual
TX level set by generating 1khz tone with "cop 4" command in asterisk and
adjusting output for 3khz on service monitor.

All sites are running DIAL, everything is private node numbers and private
IP space (no network congestion since we aren't sharing with anything else).

The RTCM is using external CTCSS input from the Kenwood on pin 24 of the
AUX connector and pin 24 is set to "TOR".

The squelch crash is usually only a problem on weak signals, or very short
(kerchunk) bursts.
I have included a short video showing the problem on a test bench.  The
video shows the transmit/receive LED on the HT, and the LEDs on the RTCM.
It's very clear that the receive signal is gone and CTCSS has dropped while
the transmitter is still held on to transmit the squelch crash.  The video
shows a clean transmission, followed by 2 crashes simulated with a double
"kerchunk".  The mountain top repeaters squelch crashes are upwards of 1
full second of audio after the incoming transmission has stopped.

I am wondering if I don't have enough CPU on the DIAL box?  Is it possible
that I just don't have enough to do the DSP processing fast enough?

Any tips after seeing the video much appreciated.  Thanks!!

James
KI0KN

video url:   http://ki0kn.com/wp/blog/
(please excuse the barely setup wordpress page!!)
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