[hpsdr] FM squelch

[Warren C. Pratt]

Hi Alf,

I got out the FM signal generator and did a quick check.  All here seems 
to be working as expected.  Setting differences could be the issue.  The 
thing to check first is the sample rate.  Because of the bandwidths 
involved in FM demodulation and modulation, I would not recommend using 
less than a 192K sample rate for FM.  DSP Buffer Size might also be 
relevant.  At 192K, I'd use 4096.

In any case, if you are still having difficulty, you've found the 
workaround for the moment -- the squelch OFF button.

Let me know if sample rate / DSP buffer size helps.

73,
Warren  NR0V

On 8/2/2014 4:34 PM, Alfred Green wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> On 8/2/2014 1:50 PM, Ken N9VV (Win-7/64) wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> I am not sure that I can offer you a good explanation about this Alf, 
>> but you might want to use a calibrated signal source like the 
>> Elecraft XG-1 which emits a 50uv = S9 = -73db signal at 7040, and has 
>> another setting of -113db = S1 = ?uv with a switch.
>>
>> You can then know that your receiver is properly calibrated with any 
>> sort of input. I believe some of the more modern Elecraft calibrators 
>> allow you to select any frequency you wish.
>>
>> Perhaps you could substitute the calibrated signal for the IF signal 
>> coming from the transverter, and then adjust the SQUELCH on/off and 
>> level slider as needed to verify it's tripping levels in your setup.
>>
>
> Tnx for the comments, Ken.
> The IF is well calibrated; in fact I have good sources through 10Gigs 
> so that is not the issue.
> When you mentioned "adjust the SQUELCH on/off and level slider"  I had 
> an 'ah-ha' moment; clicking on the 'SQL: xx' box turns on/off the 
> squelch. I had forgotten that was a control, but it does exactly what 
> I needed.
>
> Maybe I should just RTFM.
>
> GL & 73,  Alf  NU8I
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