[Elecraft] PX3 Spike won't go away

[Don Wilhelm]

Brian,

The answer is *bonding* as described by Jim Brown K9YC for minimizing 
noise, hum and buzz.
Connecting everything to a common point may actually make the situation 
worse (see the K9YC papers).  "Grounding" everything will not minimize 
noise, hum and buzz.  Mother earth ground is not a 'sink' for RF, noise, 
hum or buzz - it is only for safety from AC mains faults or suppression 
of surges coming in on your antenna feedline.

Make your bonding follow the path(s) taken by the shields of your audio 
cables and coax and you will have better results.

In other words, bond the computer to the soundcard device (if included), 
and bond that to the KX3.
Bond the KX3 to the PX3, and bond the antenna tuner to the KX3 
(following the path of the coax).

Then you may bond the antenna tuner to your common ground point for AC 
mains safety and lightning protection.

The reasoning behind this bonding is to conduct much of the noise, hum 
and buzz to the *outside* of the equipment enclosures rather than having 
it conducted onto the ground plane of the PC boards.

In the long past, we did not have those problems.  Connectors were 
mounted on the enclosure chassis, and any noise, hum or buzz would be 
conducted onto the outside of the enclosure where it was not likely to 
cause any harm.

With modern construction techniques, the connectors are mounted to the 
PC board inside the enclosure (and not to the outside of the 
enclosure).  That means that any noise, hum and buzz that is picked up 
on the shields of AF cables or coax will be conducted directly onto the 
ground plane of the electronics.  The bonding between enclosures in 
parallel to the audio and RF paths drastically reduces the coupling of 
that noise, hum and buzz onto the circuit board and lets it flow 
harmlessly onto the outside of the enclosures.   This is the "pin 1 
problem" that K9YC refers to.

If you do equipment to equipment bonding and bond the final element 
(amplifier or antenna tuner) to your station ground, everything in the 
station will also be grounded - assuming you use heavy wire or strap for 
the equipment to equipment bonding - the shield stripped from old RG8 
coax will do nicely as will #12 or larger wire.

Try it, it works.

For those who ask how to bond to a laptop computer, my answer is "any 
way you can" - if you have a jackscrew for a VGA connector, that is an 
obvious point - otherwise connecting to the shell of a USB or HDMI 
connector may be your only choice - do the best you can.

73,
Don W3FPR

On 6/23/2016 7:31 PM, Brian Waterworth wrote:
> I disconnected the USB acc1 cable from the small computer I was planning to
> take with me to FD and the noise vanished.  Each of the computer, the kx3,
> px3, external power supply, external antenna tuner are all grounded to a
> common point.  The exception is the monitor and fan (it's going to be hot
> :-).
>
>