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

[Dick Lichtel]

I also am seeing the spurs using a an Astron linear supply with my 
Hermes + ANAN-10

For reference CuSDR shows nearly a S7 on 10Mhz.

I disconnected the RX cable on Hermes, but didn't see any change in any 
of the spurs. I left the TX cable in place.

I pulled  the Hermes card out as far as I could from the case (about 1/4 
board length, which about the most I can do without disconnecting the 
power cable) and saw the spur signal strength drop down to around an S3. 
This affects only the 10MHz and harmonics, but not the 24.5MHz spur or 
the 49MHz spur.

Dick KD4JP

On 11/11/2012 6:55 AM, Bruce Beford wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> 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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