A simple single pole double throw switch will work. Get a small radio
shack junction box, run the output of each radio into it, mount the switch
in the box, run the output to the speaker.

Eric

"Tamaroak" wrote in message
. ..
I have two VHF radios, both of which have a PA and foghorn mode and will
send a 20 watt signal into a horn mounted on my flybridge. Standard Horizon
says I can't just hook the two of them to the same horn becxause the one
radio will backfeed into the other, causing it to be harmed.

The solution is to get two diodes and wire them on the + wire before it
gets to the horn.

Question: What kind, size, specifications do I use for said diode? The guy
at Radio Shack looked at me like I was from Mars, when I asked him this.

Capt. Jeff