It happens on my wire 75 meter dipole antenna that runs right over my roof. Yes, I have a dual ferrite core 1 to 1 balun on my coaxial feedline at the antenna feed point. At 100 watts out I am fine, but once the amp is on it happens. I am running an ALC Line to the amp and have the ALC adjusted correctly. No USB cable hooked to the radio
There is a small possibility that your 75 meter balun is saturating when running QRO. It is not common but it does happen depending upon construction details.
I would add a common mode choke where the coax enters the house.
You should also add common mode chokes to all cables in and out of the router. Some type 31 ferrite is the best choice. Type 43 is a close second.
Don't overlook having the provider come back to check their installation. Bad connectors, etc. can also cause these problems.
- Glenn W9IQ
The Balun is a Balun Designs dual ferrite core 1 to 1 choke balun. All connections are tight, and since my dipole is coaxial fed, it is installed right at the feedpoint.
My Amplifier is a solid state Ameritron ALS 1300. It only puts out 1200 watts on peaks, so the Balun SHOULD be well within it's limits. SWR is a little bit over 2 to 1, but since it is 75 Meters and I use a tuner, I have not bothered to trim it down to 1 to 1.
What is really weird is back when I had Frontier Internet, I had zero problems!
It was not until the switch to Spectrum that all the **** started.