[Elecraft] HRD digital USB wire to K3/KPA500 lockup?

[Joe Subich, W4TV]

Absolutely textbook example of common mode (conducted) RFI on the
antenna cable.  See the K9YC and GM3SEk documentation on common
mode chokes.  In your case, I'd suggest one at the remote tuner
and one at the ground rod where your feedlines enter the shack.

The problem occurs because the RF voltage on the *outside* of the
coax follows the shield of the USB cable to the computer - if the
voltage is high enough the negative swings fool the computer into
thinking the USB cable has been unplugged and Windows disconnects
it.  A few toroids on the USB cable will not necessarily do the
job - get rid of the RF at the source (antenna/entry).

73,

    ... Joe, W4TV


On 2/10/2014 9:31 AM, John Fritze wrote:
> Anyone having this problem?
>
> This is everything I can think of:
>
> When running digital, my computer looses contact with my
> K3/P3/KPA500/KAT500.  In other words, DM780 stops working necessitating
> shutting down HRD, pulling and re-plugging in the USB connection,
> restarting HRD.  Sometime the K3 is locked in transmit and needs to be shut
> down too because I have no response from any of the buttons.  It doesn't
> seem to matter what power output I run.  I will sometimes get an error
> message about serial stopped working.
>
> I am thinking this is an RF problem, but have not been able to locate and
> solve it.  I have wrapped multiple turns of the USB/serial cable on a mix
> 31 toroid, rechecked my house and antenna ground system.  The antenna I am
> using is a remote tuned vertical about 90 feet away with 35 ground radials.
>   Computer is a laptop (I have several with XP, W7 and W8) doesn't make any
> difference which one I use.
>
> The KAT500 has 2 antennas connected, the vertical and an OCF dipole (rarely
> used).  The tuner is only used when using the dipole.  Is it possible there
> is not enough isolation between the antennas?
>
> All coax is RG8, except in the shack 8U for the interconnects between K3
> and KPA500.
>
> This problem doesn't happen when using FLdigi.  But then I need to log
> manually or am using N1MM in contests.
>
> Shack is on the 2nd floor, grounded through the copper radiator system, and
> jumpered to 2 separate ground rods in basement.  All equipment is connected
> to one common ground using 1 1/2" braid.
>
> All rig interconnects are Elecraft.  No 3rd party.
>
> HRD is latest version.
>
> I been scratching my head over this for several months.
>
>
>