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

[Bruce Beford]

Thanks very much, Dick.
Your description will help me with my implementation. It will be interesting
to see if the 10 MHz spurs are significantly different when using an
external GPSDO reference instead of the onboard TCXO. I had planned on
adding a DPDT toggle switch that would connect the external ref, and disable
the on board one. It would connect to the jumper pins provided for this
purpose. I'll study the physical layout a bit on that. I'll need to include
that under the shield.

Bruce, N1RX



-----Original Message-----
From: Dick Lichtel [mailto:dick221z at gmail.com] 
Subject: Re: [hpsdr] Hermes/ANAN-10 RX spurious signals?

I didn't take any pics but the implementation is pretty simple.

Materials: Brass Shim sheet from Ace hardware , though pretty much 
anything that can be soldered to can work.
                    Solder wick braid, used to ground the shield.
                    Double sided tape, used to support/insulate the shield.

I cut a piece of brass to fit over the 10 MHz area, it sits on top of 
the jumpers.  There isn't any need to cut holes in the shield, its just 
a rectanglar piece.

With the board positioned with the 10MHz SMA jack(J25) facing up, the 
shield  fits between J8/J9 (doesn't cover those jacks) on the left  
extends to J24 on the right (J24 is covered) . It rests on the J16 leads 
at the top and covers the 122 Mhz Osc  at the bottom.  I soldered a 
piece of braid from to the alignment hole on next to the 10MHz SMA jack 
(J25) to the shield. The connection to ground should be as short as 
possible.

All the jumpers/leads in the area (J20/J22/J23/J24 and the leads on J16) 
should be covered with tape. There is a small piece of tape  placed on 
the 122 MHz for support on the bottom left corner. For the bottom right 
corner, there is stack of double sided tape. For the stack of tape, I 
didn't peal off the covering, so it doesn't leave sticky stuff on the 
caps & resistors.

With the shield in place, the 10Mhz spur + harmonics are completely gone.


Dick KD4JP

  I have not found any means to reduce the 24.5Mhz spurs. I think this 
will require some support from Apache Labs.






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