[hpsdr] PureSignal and ANAN-10

[Rob Crewson]

Hi John,

   I cannot talk to the cross talk in the ANAN-10 but I have seen it in my
TAPR Hermes and in the past in my TAPR Alex box.
  The following points were first pointed out in the reflector  by Graham
Haddock KE9H.
   When Alex first came out the boxes themselves became part of the problem
because they are anodized aluminum surface (read insulated surface).
   Even the board to case grounding was not a sure thing unless one to steps
to actively connect leads between the board grounds and the screws that hold
the end plates.
   
   On the Hammond case for Hermes my first tests with an ohmmeter showed the
same insulated property. 
   I built up solder on the 4 grounding mount holes on the Hermes board but
this is not much more of consistent contact with the case than before.
   So I will be adding wires from them to bring out to the end plate screws
as was done on Alex. 

   Four star washers under the screws for each end plate fixed the ground
continuity between endplates and case.
   But I  still detected RF from it on my Atlas machine and I remembered
then that the sliding lid was also insulated from the reset of the box.
   So 2 small metal screws (not the black anodized type) were added to each
side of the sliding lid at the join to complete the continuity. 

  The ANAN -10 case looks anodized to me in the pictures so it could be a
source of the problem.

  Hopes this is useful info to someone.

73,

Rob  Crewson VE3EW


-----Original Message-----
From: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of John
Ackermann N8UR
Sent: Sunday, July 20, 2014 4:44 PM
To: hpsdr at lists.openhpsdr.org
Subject: [hpsdr] PureSignal and ANAN-10

***** High Performance Software Defined Radio Discussion List *****

I've been playing with PureSignal and it definitely works!  Using an
external spectrum analyzer, I'm seeing a 10dB 3rd order IMD improvement at
100W PEP.  But I'm not sure if I've optimized the system.

I'm using a TAPR Hermes mounted in an ANAN-10 enclosure/amplifier.  The 10W
output drives a TenTec 418 amplifier to 100W.  However, I'm seeing a
crosstalk issue similar to that reported for the ANAN-100.  I'm wondering
whether anyone else has experimented with the ANAN-10 configuration and seen
this.

I measured the signal present at the "RX IN" SMA connector with the
ANT-1 BNC connected to a dummy load.  The signal ranges from -37dBm at 160M
to -8dBm at 6M.  (As usual, I've done a bunch of measurements and
screenshots, and written up what I've learned so far at
http://www.febo.com/pages/hpsdr/puresignal.)

This makes sense when you consider that the amp/lpf board is mounted
parallel to Hermes and only an inch or so away.  But it means that the
sampled signal needs to be pretty strong to overcome the crosstalk.

I have three questions today:

1.  Has anyone else done similar work with their ANAN-10?

2.  How much stronger (in dB) should the sampled signal be than the
crosstalk, in order to make sure that PureSignal is correcting the whole RF
chain rather than just the ANAN-10 amplifier?

3.  Given the ANAN-10 antenna configuration, it appears that feeding the
sample into the SMA "RX IN" connector is the only way.  Am I missing
something?

73,
John
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