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

[Berndt Josef Wulf]

G'day Dick,

you also could use a single layer copper cladded PCB cut to size with
the copper turned to the "safe" side.

73, Berndt
VK5ABN

On Mon, 2012-11-12 at 20:56 -0500, Dick Lichtel wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> I looks like the 10MHz noise can be reduced from an S7 to an S2 by 
> placing shielding over the 10MHz osc area. I tied the shielding to 
> ground via copper foil tape to the 10MHz Clock  SMA connector.
> 
> The 10MHz osc is directly below the ANT1 input on the amp causing the 
> clock to couple with the RX input... which is why moving the Hermes 
> board in and out of the cabinet changes the noise strength.
> 
> It might be possible to place a shield in a slot  above the Hermes board 
> in the cabinet. I only needs to be about 2" in depth. I'm thinking that 
> a piece of brass or copper  from ACE hardware could be cut down to size 
> to fit. It is probably a good idea to coat the metal with something not 
> conductive to be safe. I'll try this tomorrow to see if the results are 
> similar to placing a small shield over to the osc. area.
> 
> I suspect a similar approach can be taken for the 25Mhz clock, but I 
> have to look at the schematic and board layout in be sure.
> 
> I think it was a bad idea to have the Hermes board face up in the 
> cabinet. The spurs probably wouldn't be there and we won't have to 
> solder those tiny rf connectors. We would need to new face plates to 
> mount the Hermes board backside up.
> 
> Dick KD4JP
> 
> On 11/12/2012 6:17 AM, Bruce Beford wrote:
> > Thanks, Dick.
> > I am glad you have had a chance to experiment with this a bit. I won't be
> > able to work with mine for a week. Please keep us posted on your
> > progress/observations.
> > 73,
> > Bruce, N1RX
> >
> > ________________________________________
> > From: Dick [mailto:dick221z at gmail.com]
> > Sent: Sunday, November 11, 2012 10:11 PM
> > To: Bruce Beford
> > Cc: hpsdr at lists.openhpsdr.org
> > Subject: Re: [hpsdr] Hermes/ANAN-10 RX spurious signals?
> >
> > 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.
> >
> > I'll look into making something more practical that can be grounded later on
> > in the week.
> >
> >
> >
> >
> >
> 
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