Lowering My Noise Floor

[KC1BAQ]

Lesson learned: My laptop power supply was adding 4 S units to my noise floor through my CAT control cable to the radio.

I was moving some cables around in my shack last night in an attempt to tidy things up a bit. When I unplugged my CAT control cable from my laptop, the noise floor on my radio dropped 4 S units on 80M (I just happened to be logged into an 80M net). I plugged it back in and the noise came back. Snap on ferrite beads did not help. So I plugged the cable into the USB port on my Apple macbook and there was no noise. This told me that it was not the cable, but a problem with my windows laptop. Next I unplugged the power supply from my windows laptop and the noise disappeared. I unplugged the power supply from the power outlet and the noise disappeared. After plugging it back it, all was quite for about two seconds and then the noise returned. This told me that the power supply was generating RFI after the charging circuit turned on. I had two snap on ferrite beads sized for coax and wound three turns on each, but still there was noise. Fortunately, I had purchased a large type 43 torroid for a balun project a while back and made 10 turns on the cable from the power supply to the laptop. The noise has now disappeared!

I hope this might be helpful to others in the same situation. Unplug your power supply from the wall outlet and see if your noise floor drops on any of the bands. Picture attached.

73,
Joe