I'm not particularly skilled or knowledgeable in the context of amateur radio, but I am a helluva researcher, and your interests happen to at least momentarily coincide with mine, so I'll look into the matter and report back to you.
>One thing I'm mainly interested in is the "close by" function, mainly in how it works, is it effective and can it be set to only respond to memory/band frequencies or does it just respond to anything?
Right off the bat, this sounds prima fascie like something that might operate based on APRS or similar. But again, most of my knowledge is heavily black-boxed, so I'll have to do a bit of reading and get back to you.
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