Hi Ron,

I don't know how to tell for sure, but the audio extension cables that are 
available today have a very poor shield.  Try to make sure that you buy a 
heavily shielded cable as this will vastly reduce RF from getting into your 
audio lines.  You might even try using small gage coax as it has great 
shielding as long as you don't buy the Radio Shack junk coax.

Bob, K8LR, [log in to unmask]