[arm-allstar] notch filter

[David McGough]

How is this repeater interfaced to HamVoIP??  If connected via simpleusb,
you can use the "brick wall" DCS filter to effectively remove CTCSS/DCS
signaling.  See this message for more info:

http://lists.hamvoip.org/pipermail/arm-allstar/2018-May/008862.html


If you've got serious harmonic distortion on the CTCSS/DCS signaling, 
the app_rpt rxnotch function will help.  Resolving the harmonic 
distortion issue at the radio is the best plan, of course. See:

http://lists.hamvoip.org/pipermail/arm-allstar/2021-March/016490.html


Pipelined audio processing features are coming in channel driver updates.


73, David KB4FXC



On Mon, 28 Mar 2022, "Patrick Perdue via ARM-allstar" wrote:

> I have access to a repeater's Allstar node. This repeater has a 162.2 hz 
> PL tone, and it's rather loud, especially the third harmonic, not so 
> much the fundamental frequency. Aside from cleaning things up at the 
> source, which is the best solution, I've tried all sorts of things to 
> minimize that tone. That frequency is high enough that even using the 
> rather sharp PL filter, it still leaks through. I've tried various 
> stacks of rxnotch with different bandwidth, located at the center 
> frequency, and also half an octave to either side. This gets rid of that 
> harmonic, but it rings out where the notch center frequency lives. I can 
> adjust how much it resonates by changing the width or adding more 
> filters. Ultimately, I'd love to use something else to process the 
> audio, like a parametric EQ rather than a hard notch. A long time ago, I 
> read about a future iopipe driver for HamVoIP that might allow for such 
> things to be used. Just wondering what the progress on that is.
> 
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