I'm new to service monitors. I'm assuming that the handheld was run into a dummy load and the CSM was listening off of it's antenna? Or how was the radio run into the monitor?
Most all CSM's have a built-in dummy load. For this IFR CSM that would be the BNC connector on the lower right hand portion of the front of this CSM. Simply use a piece of coax that will attach to the radio's RF port (antenna port) and the other end attaches to the BNC connector. That way you can read the RF ouput, use the signal generator to send a on freq signal to the receiver of the radio along with many other things. If you are not interested in RF power reading or using the signal generator to test the receiver, then simply place a rubber duckie antenna on the IFR's antenna port, key up the radio and check for on-frequency and modulation. Hope this answers your question for you.
