[hpsdr] Hermes/ANAN-10 RX spurious signals?

[Bruce Beford]

Thanks, John. 

This is similar to what I am seeing. I am running the Hermes/ANAN-10 from a
stiff Astron linear regulated supply. I believe the spurs seen are multiples
of the 10 MHz TXCO, the 122.88 sampling clock and the 25 MHz clock for the
Ethernet PHY. 

Also, my query is not meant as a criticism. I believe the Hermes has a great
receiver, as all these "sprogs" fall outside the Amateur Bands. The one at
10 MHz is strong enough to create a pretty noticeable beat with WWV when an
antenna is connected in place of the dummy load, however.

At some point (it may be 10 days or so before I get a chance to do this) I
will obtain spectra for the terminated bare Hermes disconnected from the
ANAN-10. I would like to determine if the cables to, and the PA board
itself, act as antennae increasing the pickup of these internally generated
signals. I will do a similar re-check of my separate card-based openHPSDR
system of Mercury, Penelope, Alex, Excalibur and Metis.

73,
Bruce N1RX



>  I have a fair amount of spurs on my standalone Hermes.  But I haven't 
> done a "fair" test yet.  I'm using a reasonable quality PC power supply, 
> but since it is a switching supply it can easily be adding interference. 
> What are you using to power your Hermes/ANAN-10?

>  I also have it near other electronic equipment. Finally I haven't 
> completely enclosed the board in a metal case.  I need to try a test 
> with a  battery and some more isolation from potential noise sources.  
> However, I'm not quite seeing the same  issue with 10 Mhz multiples. I 
> see a little spur at 10 Mhz, nothing at 20 Mhz, a little spur at 30 and 
> 40 Mhz. I see a big spur at 50 Mhz.

> My biggest spurs are at fractions of the 122.88 Mhz main sampling clock, 
> i.e. 12.288 Mhz, 24.576, 36.864 and 49.152 Mhz, with the biggest ones 
> being 24.576 and 49.152 Mhz. Those are huge.

> I would think you could open your case and disconnect the ANAN-10 if you 
> wanted to check just the Hermes board by itself.

> John
> AC0ZG



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