[TheList] CCIR FENZ Selcall

Mon Jul 29 08:58:59 AEST 2019

Last Christmas holidays I came across an old post about NZFS selcall 
signalling:
http://radiowiki.org.nz/pipermail/thelist_radiowiki.org.nz/2010-December/001033.html.
That piqued my interest, and after figuring out that it is a variant of CCIR
selcall, and 6 months of tinkering, I have a Windows command line 
program that
uses audio dsp methods to decode the tones reasonably consistently.

Is there anyone on this list who would be interested in helping with 
some testing?

Development work has been done in Christchurch. I think it should work 
nationally
but I haven't had the opportunity to test it anywhere else.

You would need a Windows 7 or later PC, 64-bit, with a sound card that 
supports
48000 samples per second 16 bit mono. The program takes audio from the
default recording device configured in your Windows settings. It is 
designed to
use direct discriminator output from your receiver however it will work 
with a
speaker or headphone connection (but take care to avoid clipping).

Just to be clear, the program doesn't give direct information about 
which fire
appliance is doing what, etc. It simply decodes the tone groups to their 
CCIR
tone symbols. Output looks like this (it writes to stdout):

CDB31FFF1400C
C5DB3__44
CDB31FFF1325C
C5DB3__33
CDCC1FFF1C00C
C5DCC__CC

I leave it as an exercise for the reader to write a script or program that
converts the symbol groups into appliance name and status and so on. A 
python
script using regexes would be a good approach I reckon.

The current release also writes a raw PCM output file of the captured audio.
I have found this useful for debugging tone groups that fail to decode. You
will need some disk space to accommodate this file.

Technically an analogue 24 kHz anti-aliasing filter is required. I am 
using the
data connector on a Kenwood TM-G707 which works well without an 
anti-aliasing
filter, but your mileage may vary.

If you would like to try out the program please contact me directly by 
e-mail
and I will e-mail a copy back to you. I am not distributing the source 
code at
present; just the executable.

Cheers,
Paul