Sorting out some RFI in the shack

I noticed W1AW/4 (South Carolina) was on 80 meter RTTY last night and figured it might be a good opportunity to try and grab my first station for the ARRL Centennial QSO Party.

The guy was operating split, so I setup the K3 to transmit in what I determined was the sweet spot of the pile-up based on watching the waterfall of the P3. I fired up MMTTY and hit my answer macro, feeling confident. The SignaLink started sputtering — keying and unkeying the rig while only sending a few characters. Hmm.. that’s interesting.

I shut down everything — radio, interface, computer — and gave it another shot, this time trying it on a dead portion of the 20 meter band. Everything seemed to be OK. Back to the pile-up on 80 and crap… the SignaLink was misfiring again. I tuned a few kilo away and sent some diddles, which proved to be equally erratic for the SL. I also observed the ALC meter jumping around, well above the suggested level of drive for data work. What was interesting before, has turned into frustration. My, my, my…. this was turning into a mystery worth of Lt. Joe Kenda.

I dialed my power back from 80 watts to less than 10 watts and suddenly everything seemed OK. The ALC was normal, and the interface wasn’t sputtering. Seems like maybe RFI was haunting the shack and borking my USB interface. I decided to pose the question to my friend across town.

“Oh yeah! Big time RF there,” he tells me. His suggestions made sense: Coil excess cables (apparently RF prefers traveling along straight paths), add toroids to every cable, properly ground everything and try re-arranging the operating position.

So tonight I coiled all the longer cables, did a crude choke balun at the window jumper where the feedline comes into the shack and moved the SignaLink farther away from the rig. Testing the rig at close to full power RTTY on 80 meters looked promising. The SignaLink seemed to be functioning properly and the ALC readings looked good. Hopefully the problem has been dealt with. Looks like I’ll be ordering some toroids also.

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