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<div class="moz-cite-prefix">Since the position of the Hermes board
in the case seems to affect the 10MHz spur, I tried putting the
Hermes back in position and sliding bit of shielding over the A/D
area, about 1/2 spacing above, not grounded. This reduced the
10MHz spurs by about 2 S units. So it looks like some shielding
is needed over the analog section.<br>
<br>
I'll look into making something more practical that can be
grounded later on in the week.<br>
<br>
On 11/11/2012 5:54 PM, Dick Lichtel wrote:<br>
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I also am seeing the spurs using a an Astron linear supply with
My TAPR Hermes + ANAN-10<br>
<br>
For reference CuSDR shows nearly a S7 on the 10Mhz.<br>
<br>
I disconnected the RX cable on Hermes, but didn't see any change
in the strength.<br>
<br>
<br>
I slide the Hermes card out as far as I could from the case
(abt 1/4 board length) and saw the spur signal strength drop to
a little more than an S3. This affects only the 10MHz and
harmonic spurs, but not the 24.5MHz spur or the 49MHz spur.<br>
<br>
On 11/11/2012 6:55 AM, Bruce Beford wrote:<br>
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<pre wrap="">***** 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
</pre>
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<pre wrap=""> 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?
</pre>
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<pre wrap=""> 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.
</pre>
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<pre wrap="">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.
</pre>
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<pre wrap="">I would think you could open your case and disconnect the ANAN-10 if you
wanted to check just the Hermes board by itself.
</pre>
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<blockquote type="cite">
<pre wrap="">John
AC0ZG
</pre>
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<pre wrap="">
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