PL/CTCSS/DCS squelch on rtl_fm? - osmocom-sdr - lists.osmocom.org

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PL/CTCSS/DCS squelch on rtl_fm?

Re: Big rtl_fm (and more)...

Big rtl_fm (and more)...

Chris Hanson

13 Nov 2013 13 Nov '13

1:59 p.m.

Has anyone considered adding this or found a work around for those noisy stations that keep breaking the squelch? Thanks Chris

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Sdr Guru

7 Dec 7 Dec

9:22 a.m.

Hi GPL DCS source http://yo3iiu.ro/blog/?p=779 CTCSS & Noise Squelch http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… SG On Wed, Nov 13, 2013 at 2:59 PM, Chris Hanson <lightningbolts(a)gmail.com>wrote;wrote:

Has anyone considered adding this or found a work around for those noisy stations that keep breaking the squelch? Thanks Chris

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Chris Hanson

9 Dec 9 Dec

1:33 p.m.

Thanks for the response. I looked at the code and from what I can tell, it’s just using various ham radio rigs built in CTCSS facilities and programming them via RS232. Am I missing something? Chris On Dec 7, 2013, at 3:22 AM, Sdr Guru <sdrguru1(a)gmail.com> wrote:

Hi GPL DCS source http://yo3iiu.ro/blog/?p=779 CTCSS & Noise Squelch http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… http://svn.ohnosec.org/viewvc/projects/allstar/astsrc-1.4.23-pre/trunk/aste… SG On Wed, Nov 13, 2013 at 2:59 PM, Chris Hanson <lightningbolts(a)gmail.com> wrote: Has anyone considered adding this or found a work around for those noisy stations that keep breaking the squelch? Thanks Chris

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James Sharp

7:17 p.m.

On 12/9/2013 7:33 AM, Chris Hanson wrote:

Thanks for the response. I looked at the code and from what I can tell, it’s just using various ham radio rigs built in CTCSS facilities and programming them via RS232. Am I missing something?

The app_rpt file has some functions to detect tones in an audio stream that can be used to detect the CTCSS tones. Look through the "tone_detect" function along with the goertzel_* functions. They're not specifically tagged as functions to decode CTCSS tones, but they should be able to be used as such. Those functions are expecting to be fed a 16-bit signed linear mono audio stream.

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Nick Foster

7:30 p.m.

For transmitters that don't use tone squelch, the best FM squelch is a noise squelch, which detects the "quieting" an FM signal causes. The gr-scanner project (which is incomplete/work-in-progress, don't bug me about functionality yet) has one, albeit written for Gnuradio: https://github.com/bistromath/gr-scanner/blob/master/python/standard_squelc… It's a rewrite of Gnuradio's "standard squelch". --n On Mon, Dec 9, 2013 at 10:17 AM, James Sharp <james(a)fivecats.org> wrote:

On 12/9/2013 7:33 AM, Chris Hanson wrote:

Thanks for the response. I looked at the code and from what I can tell, it’s just using various ham radio rigs built in CTCSS facilities and programming them via RS232. Am I missing something?

The app_rpt file has some functions to detect tones in an audio stream that can be used to detect the CTCSS tones. Look through the "tone_detect" function along with the goertzel_* functions. They're not specifically tagged as functions to decode CTCSS tones, but they should be able to be used as such. Those functions are expecting to be fed a 16-bit signed linear mono audio stream.

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Chris Hanson
James Sharp
Nick Foster
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