Thread: One channel, different frequencies?

Correct

Hi,

Exactly right.

It is called DUPLEX. Both (mobile) radios receive on the designated Ch freq, say 470.575 Mhz. The repeater output is also on this freq.
The mobiles transmit on a pre-defined offset to this (argument's sake 475.575Mhz. (Happens automatically when press the Press-to-talk switch on the mic, AND you have "duplex" selected, or when it is built in to the programmed channel in the radio.)
The repeater input is also on this freq.

The signal goes from radio A to the repeater and then to radio B, and then from B to the repeater on to A for the answer.

In SIMPLEX both A and B radios have (say) 470.575Mhz for both receive and transmit, the repeater not being involved.

The radios may be programmed with the receive and transmit being the same on a separate channel to the "split" used for the repeater use, or may rely on the use of a "duplex" button.

For UHF CB, in the current situation (up till now, but possibly being changed in the expanded system coming in gradually from now on), channels 1 - 8 are duplex channels i.e. are reserved for duplex operation, and use the same
receive freqs as channels 30-38, but different transmit freqs.

Hope this helps.

rovers4

in this case its emergency services channels, transmitting on frequency A and recieving on frequency B..... essentially a simplified duplex setup then?

Yes, you can't re-transmit on the same frequency the originating transmitter is on otherwise the more powerful or closer signal will override the weaker signal.

For a repeater you transmit on the frequency the repeater station receives and you listen on the frequency the repeater station transmits. This way you effectively double the distance between the originating station and receiving stations, so long as the repeater is relatively between the two stations.