[hpsdr] FM squelch

[Alfred Green]

On 8/2/2014 7:22 PM, Warren C. Pratt wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> 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.
>
Hello Warren,

I appreciate the comments.
I'm running at 48k sample rate with 2048 rx buffer size. If I change to 
192k sr the squelch slider seems to operate more like I was expecting, 
ie. with no or little signal, setting squelch to 0 opens the Rx. That 
may be how I had it set before, so my old memory may not be failing.

However, it really isn't an issue anymore, as I have found the on/off 
button. I have now had a whopping 2 contacts on FM in the last year or 
so; usually I am on CW/SSB/JT on UHF and up. It was just that a local 
had an FM HT with him that would work on 1296, so it was worth a shot 
for a point.
If anyone is planning on using FM more seriously then the note about 
sample rate would be an important consideration.

Tnx for everything.

73  Alf  NU8I
Phoenix  AZ  DM33xo

 1407078160.0