[Elecraft] OT Hearing HRD Communicate w/K3

[Elecraft K3]

Hello Wise and Powerful Reflector;

I am experiencing a confounding problem with Ham Radio Deluxe, Digital Master 780 and my K3.  I've determined that HRD polling the K3 is introducing a croaking pulse-like noise into my signal chain.  I know it is HRD because if I quit out of HRD, no noise.  In fact, if I merely click and hold on the Radio pane in Digital Master 780, the noise ceases.  Additionally, if I click and hold on the Sound Card Pane, the noise also ceases.  I assume this is because that action arrests HRD's polling of the K3.

I hear it on transmit and I know it is going out with my signal because I've tuned my TH-F6A to the transmit frequency and gone out on the deck and heard it in the TH-F6A's receiver.

I assume the noise is coming in on my various antennas because pulling the antenna jack causes the noise to cease.  Pulling the audio cables does nothing.  I hear the noise on the K3's RX on some bands but not on others.  Where I really hear it is on the TX monitor when the Line in is set high and the computer's sound card is set low.  If I try the reverse - set the Line In to 2 and the sound card on the computer to 100, I can barely hear the noise.

That has been my workaround when on PSK lately but I would like to eliminate this noise altogether and keep my signal clean.

Interestingly this doesn't show up as distortion on my external IMD meter from KK7UQ.  I guess the noise is too wide and not a distortion product.

I'm thinking a ferrite toroid on the antenna coax might solve this.  I tried one of those clip on ferrite dealies with no joy.  So the question is: does anybody on the list have any experience like this?  Is a toroid a good idea?  Which one and how many turns?

TIA

73 de Eric, KG6MZS