[Elecraft] RF feedback problems with P3 and external keyboard

[Gerald Manthey]

I had RF problems with my P3 Keyboard also. I also used snap on mix 31’s and solved the problem. Then decided to use a wireless keyboard and that solved the problem. I felt the rf was getting in by the order as it was a cheap keyboard and the cord was very thin. 
Hope this helps you with some ideals
Gerald


From: Kevin Stover, AC0H
Sent: Sunday, November 26, 2017 10:54 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] RF feedback problems with P3 and external keyboard

The mix of the toroid's used does matter. Mix 31 is best.

Here is what I did with a USB mouse.
I bought four mix 31 snapon's and installed two 18 inches back from the 
mouse and another pair 18 inches back from the connector, winding as 
many turns as would fit. I bought a USB extension cable and wound most 
all of it on a mix 31 2.4 inch toroid. This choke was installed on the 
computer end and the choked mouse cable was plugged into that.

All of this assumes you have things properly bonded, especially the 
computer case/chassis.

On 11/24/2017 2:34 PM, ANDY NEHAN wrote:
> After LOTS of experimentation I think I have found that just recently I have some RF feedback into the usb keyboard on the rear of the P3. This manifests itself particularly badly with the Genovation keyboard but is also present with a standard usb keyboard. Oddly enough it is MUCH worse when using the Perwerx psu than my linear psu - but that may of course be due to different cable layout for the power cables. I have applied clip on ferrites with great enthusiasm but to no avail.
> I noticed a message on my external vga screen saying "usb device removed" shortly after starting to transmit and then shortly after that (but whilst still transmitting) "usb device connected". This is also not present when on low power (say 5 watts) but reappears at 20 watts.
> Has anyone else experienced this problem??
> Andy
> 
> 
> 
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-- 
R. Kevin Stover    AC0H
FISTS #11993
SKCC #215
NAQCC #3441
ARRL
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