I was trying to see if it could be used on a railroad radio system were they talk on one frequency then receive on another. I not sure if it can be used that way or if it's intended to be used for repeater input and output situations.
I tried using the duplex function with 2 railroad frequencies. Dispatch-Train and Train-dispatch and the offset value wasn't available in the R20 so it won't work in that situation.
I was just expereimenting to see how the Duplex operation would perform in the R20 using those frequencies.The offset value that would be needed isn't selectable.I normally monitor those channels the way you just desribed.