[hpsdr] Distorted audio

[Chris Smith]

Hi Jeremy

I was being rather lazy with my language re phase lock. You are correct that the LEDs simply indicate the difference between the external input and the internal oscillator. I had been used to seeing the LEDs change colour very slowly indicating that the internal oscillator was very close in frequency to the external Thunderbolt reference. Now both LEDs appear to be on (actually switching colour at a frequency too high for my eyes to differentiate).

I tried moving the jumper on Excalibur so that the internal oscillator was used but that didn't alter the distortion.

I will try your suggestion of removing Excalibur and configuring PSDR to select 10MHz from Mercury later this morning. If that cures the problem have you any recommendations as to where to start looking on Excalibur? The only common signal path involves U2 and the 3v3 regulator which supplies it. The o/p from the BNC socket at 1V RMS looked clean on an old 'scope but the timebase only goes to 0.5uS per div.

I'll check all the regulators while I'm at it.

Thanks.

73 Chris G4NUX

On 10 Aug 2011, at 03:17, Jeremy McDermond wrote:

> On Aug 9, 2011, at 11:51 AM, Chris Smith wrote:
> 
>> ***** High Performance Software Defined Radio Discussion List *****
>> 
>> Hmmm...  I've just turned on my HPSDR kit for the 1st time in about a month and was horrified to hear a very distorted audio output. CW signals sound like T4/5 report.
>> 
>> I haven't yet 'scoped the 13.8V line or the various O/Ps from LPU but everything seems to be working except Excalibur has lost phase lock with the Trimble Thunderbolt reference and no amount of tweaking the trimmer on X1 will pull it back into lock.
> 
> I had the TCXO go out on my Excalibur causing it not to be able to correctly lock up.  It caused a persistent warble in the signal because Mercury was valiantly trying to phase lock to the 10MHz signal.  You might try taking out Excalibur and using Mercury as your clock source and see what happens.
> 
> My understanding is, though, that Excalibur doesn't phase lock your external clock to the X1 oscillator.  The jumper chooses either one or the other, processes it into a square wave, and puts it on the Atlas bus C16.  The LEDs merely indicate the difference between the external input and the internal oscillator.
> 
>> Any ideas?
>> 
>> Chris G4NUX
> 
> --
> Jeremy McDermond (NH6Z)
> Xenotropic Systems
> mcdermj at xenotropic.com
> 
> 
> 
> 


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