"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.

If the horn is 20 Watt and your battery is 12V, you'll need at least a 2 Amp
diode. Ask for a 50V/5A diode and you'll be fine. Higher specs on voltage
and/or current are fine too if that is what is available. The price
difference should be negligent. We're talking about a sub-$ component here.

Meindert