[Elecraft] K3 serial cable shielding / noise question

[M1PAF]

Hi list,

Bit of a strange issue here with serial comms between the PC and the K3.
First a bit of description about my set up: I use an external noise sense
antenna in addition to the main station antenna to cancel out some nasty
local electrical noise with a Timewave ANC-4 noise phasing unit. This is
connected to the RX out / RX in jacks on the transverter interface (this is
a great feature).

The issue I have is this: when I use a USB serial adapter I get no
additional noise issues when the computer is polling the rig. However, my
computer has a serial port which I would rather use. I made up a cable with
pins 2, 3, 4, 5, and 6 straight through and the cable shield soldered to the
shell of the d-type that connects to the K3. When I use this cable the radio
picks up bursts of noise from the noise sense antenna (which is not good if
I'm using it to null out other local noise).

This is obviously radiation from the serial cable but I'm at a loss as to
why (incidentally also tried some ferrites on the cable and they made no
difference).

Any suggestions?

Thanks Paul M1PAF

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