RF feedback problems with P3 and external keyboard

[G4HUE]

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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[Alan - G4GNX]

I haven't connected a keyboard to my P3 yet, but I have had issues with the
shack PC.

It's been fine on 160m thru 20m but I had issues above 20m when I changed
keyboards. As the original keyboard that I used was OK re-connected it and
forgot about it.

Last Wednesday with the original keyboard connected, I was on 20 metres when
the lights on the keyboard went off and there was no output to the PC. I
found the cure was to use a large Type 31 ferrite ring and wind 4 turns of
the keyboard USB cord onto it, right close to the USB connector at the PC
end.

Perhaps this will help you with your P3 issue.

73,

Alan. G4GNX

-----Original Message-----
From: ANDY NEHAN
Sent: Friday, November 24, 2017 8:34 PM
To: [hidden email]
Subject: [Elecraft] RF feedback problems with P3 and external keyboard

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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[kstover]

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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[KC6CNN]

CONTENTS DELETED

The author has deleted this message.

[Jim Brown-10]

Good advice, Kevin, especially winding as many turns as practical.  I
wouldn't add the extension unless a choke without it didn't solve the
problem.

73, Jim K9YC

On 11/26/2017 8:52 AM, Kevin Stover, AC0H wrote:

> 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.

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[Brendon Whateley]

I might suggest that folks do not neglect that the RF may be getting into
the keyboard, causing its microcontroller to crash. Remember that we live
in an "Everything is a computer" world.

- Brendon
KK6AYI

On Sun, Nov 26, 2017 at 10:22 AM, Jim Brown <[hidden email]>
wrote:

> Good advice, Kevin, especially winding as many turns as practical.  I
> wouldn't add the extension unless a choke without it didn't solve the
> problem.
>
> 73, Jim K9YC
>
> On 11/26/2017 8:52 AM, Kevin Stover, AC0H wrote:
>
>> 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.
>>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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