[arm-allstar] notch filter

[Patrick Perdue]

Yep, audio coming from the repeater. Of course, cleaning the audio up at 
the source is always the best idea. They're using a Yaesu repeater, 
which already doesn't have spectacular audio, and there are harmonics 
all over the place in the PL tone, so a simple notch doesn't really help 
much.


On 3/29/2022 9:39 AM, "Rick Dykstra via ARM-allstar" wrote:
> Are you talking about the audio coming over Allstar when you connect 
> to the repeater node? Is this someone else's repeater?  If so, it 
> would be better to talk to the owner and remove it at the site, or 
> everyone else will have the same problem you do.
>
> Rick KR8T
>
> On 3/28/2022 11:41 AM, "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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