Shack RFI Adventures Part 3 – 40m

Every time I think I have the RFI problem ironed out, I move to another band, and have to chase it all over again.

Sauntering my way over to 40m recently gave me a repeat of the RFI gremlins vexing my laptop, and thwarting my rig control and laptop USB communications, similar to the chase I already had with 20m and 30m. I guess this is where it really gets driven home that radio frequencies are electrical creatures that behave differently as the frequencies change.

On 20m, I was able to suppress these issues using ferrite beads on all the cables to the radio, and from the radio to laptop and my SignaLink.

On 30m, I had to play with radials, and switch USB cables among other things on top of the 20m “interventions”.

On 40m I started with adding a commercial choke by LDG just inside the feedthrough panel, and a longer radial wire.

But that still wasn’t enough.

I could only get about 10-12watts forward power out of the radio before the RFI backlash started to wreak havoc on the rig control!

I started wondering if this could be a side effect of my lack of grounding connections on the radio.

Since I live in an apartment on the third floor, I don’t have a way to get a cable and grounding rod all the way down to the ground along the outer wall. And no, I don’t have a metal water pipe close enough to make the connection.

So I’ve been running without a ground connection.

That seemed to work okay with a lower power radio. The G90’s 20watts was pretty easy to handle without one.

But using a radio with a lot more wattage like the Icom 7300 really seems to need the RF ground.

So what’s a ham to do?

On a forum I found a feasible suggestion that I was able to implement this evening.

And the answer is……

Add another 1/4wl radial– but connect it to the radio’s ground lug, instead of to the antenna, and run it down the back of the desk, down the table leg, and from there around the baseboards in the room.


Now I can push the radio up to about 40watts digital on 40m.

It still freezes the laptop trackpad during transmission, but doesn’t wreak havoc on the rig control anymore, requiring a reboot of laptop or radio to get back on the air.

Forty meters is a lot more fun when you can actually use enough power to be heard!