"Cub Driver" wrote:

My Garmin 296 causes a hiss in the Vertex handheld sufficient to make
the radio unusable when they are mounted close.

Where does the interference come from? If I use the remote antenna on
the Garmin, will that suffice, or do I have to separate the two boxes?

Hmmm! My Icom handheld kills my 296!

Try the remote antenna; it works better, anyway.
--
Dan
C172RG at BFM