On the UHF band “REPEATERS” (also called Range Extenders) are used to help extend the range that people can talk. This is necessary because at UHF frequencies signals only travel “line of sight” and so they are easily blocked by hills, buildings, etc. A repeater is usually situated on top of a large hill or building, and therefore has a much greater “line of sight” and so can reach, and hear, signals from much farther away.
But what many people do not understand is that to do this a repeater needs TWO channels. Many people on UHF CB know about repeaters that operate on channels 1 to 8, but what they don’t realise is that these repeaters also use channel 31 to 38. This is because a repeater simply re-transmits the signal that it receives on its “Input” channel.
UHF CB Repeaters are licensed by the Australian Communications and Media Authority (ACMA). For a list of currently licensed UHF CB Repeaters and their location, visit http://www.tropinet.com/uhf-repeaters or if you wish to can search the official ACMA Register of Radiocommunications Licences.
How Repeaters Work
To understand repeaters a little better here’s some simple pictures.
Figure 1 is basic “Simplex” operation – talking to another person on a single channel such as channel 40, or perhaps 25. It is called simplex because only one channel is used to communicate.
Figure 2 is also “Simplex” but this time the stations can’t hear each other because the signal is being blocked.
Figure 3 shows “Duplex” or Repeater operation. TWO channels are used with the station that is sending or transmitting using channel 35, and the other station receiving that signal at the same time on channel 5 (This is a 5/35 emergency repeater). When the first stations finishes sending his information the reverse will occur, with the station sending always transmitting on the higher channel while other receive the signal from the repeater on the lower channel.
When you select “Duplex” or “Repeater” or “Range Extender” on your radio, and also select a channel between 1 and 8 (or 41 to 48), the radio automatically changes channels when you transmit, and then changes back when you start receiving. This is why most people do not realise that they are indeed using two channels, because they have no knowledge of what happens it is all automatic.
Repeaters always use an input channel 30 channels higher, so channel 1 repeaters also use 31, 2 / 32, etc, up to 8 / 38. Since the introduction of 80 channels there is a second repeater band – 41 / 71, 42 / 72 up to 48 / 78. If you are using one of the input channels to chat you will not hear the repeater, but it will hear you and so will everyone else that is listening to that repeater!
Radio Checks on Repeaters
When someone gives a “radio check” (a report of how well your signal is received) they will give you a report based on their location, in other words how well your signal is reaching them. This works on simplex when the signal is travelling direct from you to them, however with a repeater the signal is being received by the repeater, and then the repeater signal is received by them. It is therefore more accurate when reporting someone’s signal on a repeater to tell them how well their signal is being received by the repeater, at the repeater’s location, and not by you at your location.