[Elecraft] P3 SVGA interference -

[Arthur Burke]

Is it possible the ribbon cable is as long as it is because it will need to
eventually be routed around something else to be added later?

Art - N4PJ



On Tue, May 29, 2012 at 2:10 AM, Bob Lanning <Bob.Lanning at verizon.net>wrote:

> In response to my message May 23, 2012; 3:27pm on the Elecraft P3
> reflector Roger White W5RDW in Murphy, Texas responded off-list.  He had
> the same problem I described.  It was not coming from the K3 but from
> inside the P3.  We both noted it started after installing the SVGA.
>
> During our investigation we boy found:
>
> 1 - the signal is about 5kHz wide
> 2 - it moves either up or down in frequency ever so slowly
> 3 - moving the VFO does not change the position of the signal - internal
> to P3?
> 4 - reach back and approach the IF signal coax between the K3 & P3
> causes it to temporarily go away
> 5 - sometimes touching the P3 cabinet caused it to disappear
> 6 - changed out the coax but it still happens
>
> When the signal crosses the VFO frequency no sound is heard - only the
> signal being listened to.  But reaching back in the proximity of the
> linking coax causes it to go away.  Turning PC and other gear off has no
> effect.
>
> Roger and I spent sometime isolating the source.  We found a signal was
> coupling into the IF cable inside the P3 from the ribbon cable.  As you
> can see from the SVGA instruction manual the ribbon cable is so long
> that if not dressed it goes across the P3 and pushes up against the IF
> coax in the unit.
>
> When the ribbon cable is dressed by folding it tightly keeping it well
> away from the IF coax the wondering signal no longer appears.
>
> If you are having this anomaly Roger and I recommend making the change
> to the ribbon cable as shown in the two pictures below.  It would be
> nice to have a shorter ribbon cable.
>
> 73,
>
> Bob - W6OPO
> Roger - W5RDW
>
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