[DaleHCook]

That is not an isolation transformer - it is a variable autotransformer. It provides variable line voltage to the device under test, but it does not provide isolation from the power line and ground. It sounds like you need an isolation transformer to eliminate your problem. Note that only the device under test (your radio) should be plugged into the transformer. Your signal generator and any other test equipment should be plugged into non-isolated outlets.

Some of us use a vintage isolation transformer. I use an RCA-Viz TV Isotap Model WP-26A from the 1960s. Note that the rather crudely modified power cord added by a previous owner has since been replaced.

[Image: https://plymouthcolony.net/starcity/radi...wp-26a.jpg]