Supplemental Ham Radio Post regarding Repeaters. I know that "all y'all" out there have been ruminating about, even puzzling over, what I said below about the repeater situation at my house.
("All y'all": heard recently in the waiting area at the Greensboro-High Point airport from amongst a group of men who work for Sara Lee, flying from GSO to MIA to take another plane to Central America where they will be tending to one or more factories that Sara Lee owns there. Have you heard this expression "All y'all"? I mean, isn't "y'all" enough? Where are we going with this thing? "All, all y'all", maybe? Is there some sort of insecurity among a certain segment of Southern people that the plural form of "you", which is "you", will not be enough, that "y'all" won't be enough, and we have to go to "all, y'all", so that everyone knows that we are addressing them all? I dunno.)
What you were ruminating, indeed puzzling about was this: how can a transceiver simultaneously receive and transmit a signal? (This is what a repeater does, as all y'all will recall.) Won't the incoming and outgoing signals run into each other and tear a hole in the universe through which might enter we don't know what? Ah, I didn't tell you one thing.
The repeater receives on one frequency and transmits on another. That way, we don't disturb the Force.
When I am listening to the repeater frequency on my HT, the unit is set at frequency X. When I press the button to send or transmit, the unit automatically shifts the frequency 600 hz up or down, depending on the protocol for that particular part of the band, for the length of my transmission. This frequency change is called an "offset". Similarly (congruently?), when the repeater recieves my signal on my transmitting frequency, it retransmits it on the frequency where I was doing my listening (and where everyone else listens.) Isn't that cool?
Furthermore, since repeater frequencies are finite and there are many repeaters, some repeaters are near enough each other that they can interfer with one another. So each repeater can require a particular "tone" before it allows one's signal to enter and be re-transmitted. So, when I program my HT for a particular repeater, I am required to determine whether that repeater requires an initial tone (some do not). If so, then I program my HT not only with the receive frequency and the transmit "offset" but also with the tone, which tone my HT transmits at the beginning of my transmission so quickly that only the repeater hears it. Way cool.
Some repeaters are connected to the internet. One can reach such a repeater through his PC and, by way of VOIP, transmit and receive from the repeater itself. The repeater I use most frequently is so connected to the internet. Often at night when I am listening on my HT, my base transceiver, or the transceiver I have in my car, I will hear people from all over the world transmit from the repeater who have reached it not by way of their own transceiver but via the internet.