Take the batteries out. Put your (unconnected) plug into the socket. Check
for continuity between its outer contact (barrel) and the negative battery
terminal. Many radios have jacks with plastic external rings but there is a
ground terminal inside.

"Dave" wrote in message
...
Just a quick note: it actually does have an external antenna input, I just
don't know what type of plug to stick into it. Plastic ring with metal
contact inside, looks like 1/8" mono would do it, but how would I ground
it?
Negative battery term?

Thanks,

Dave