[App_rpt-users] squelch tail

[Stephen Rodgers]

Scott Weis wrote:
>> Hi Scott,
>>
>> There could be a couple of things that could cause this:
>>
>> 1. COR always asserted from the radio, and carrier detect depending on
>> CTCSS decode only. Check for signal swing on the COR line with a
>> voltmeter or a scope and make sure it swings below 0.3V and above 3V for
>> signal and no signal conditions.
>>
> COR no signal +12v, COR w/signal 0.0v usbradio.conf = carrierfrom=usbinvert
> 
>> 2. There have been reports that when external COR is used with internal
>> DSP CTCSS decode, that the system doesn't respond as quickly as when DSP
>> is used for both CTCSS and squelch, or when an external decoder is used
>> for both CTCSS and the radio's squelch circuit is used. None of this is
>> confirmed so if you could confirm it, that would be useful.
>>
> As a test I have done:  External COR w/o PL (either internal or external) = 
> Short Sq tail, External COR w/external PL = no sq tail, DSP COR and DSP PL = 
> Really long Sq tail. ( I have radio tune rxsquelch set to 900 and RSSI is 
> 716).
> 
> I have noticed that when I do a radio tune rxnoise and I use DSP ctcss I 
> get:
> WARNING: Insufficient high frequency noise from receiver.
> WARNING: Rx input point may be de-emphasized and not flat.
>          usbradio.conf setting of 'carrierfrom=dsp' not recommended.
> but when I have ctcssfrom=no it does not give the warning.
> 
>> As a test, try using external COR and CTCSS or a combined signal and see
>> if that  eliminates the squelch tail.
>>
>> Steve
>> WA6ZFT
>>
>>
> 
> 
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Hi Scott,

I wouldn't worry about this warning as far as CTCSS decode goes
as CTCSS decoding doesn't depend on high frequency noise. This sounds to
me like there could be a logic issue inside of XPMR or chan_usbradio

This warning was something which was added to the latest xpmr code be
Steve Henke, W9SH to tune the DSP code to different high frequency noise
spectra between radios.

Have you tried fully external CTCSS decode and Squelch and did that make
a difference?

Steve
WA6ZFT