- What is a repeater?
A repeater is a radio device which consists of both a transmitter and a receiver, and of course, an antenna.
The repeater is usually located at a high place with a good "view" of the surrounding area.
The repeater's receiver is set to "listen" (receive) on one frequency (called the input frequency) while its transmitter is set to "talk" (transmit) on a different frequency (called the output frequency). In this way, the repeater can receive and transmit at the same time without interfering with itself.
The repeater is set up so that when it receives a signal on its input frequency, it automatically "keys up" its transmitter (pushes its own push-to-talk button), and repeats or resends whatever it is hearing. This repeated or retransmitted signal is sent out on the different (output) frequency of the repeater. So, the repeater is receiving and transmitting both at the same time, but on two different frequencies. Despite the word "repeat" there is no delay between the reception and the retransmission of the signal. The audio is just fed from the receiver to the transmitter directly. Sort of like holding your telephone up to a radio so the person on the other end of the phone line can hear what the radio is receiving as opposed to relaying it by just telling or repeating what you heard from the radio.
- So what's the point of all of that?
Well, let's say that you have a handheld radio transceiver (walkie talkie). The unit doesn't put out all that much power, and besides, the little "rubber duckie" is a pretty poor excuse for an antenna. But you really would like to talk to that friend across town, or across the state somewhere. It doesn't seem like that could happen, now does it?!
- Well, maybe it can, with the help of a repeater.
If your radio (handheld or mobile rig or base radio for that matter) is set up to transmit on the repeater's input (listening) frequency, and your radio is also set up to receive on the repeater's output (transmitting) frequency, then, when you key up your radio, the repeater will "hear" your transmission on its input frequency while it repeats or retransmits your signal on its output frequency. The difference between these two frequencies is known as a split or repeater offset. Almost all VHF and UHF ham radios are set up to allow this type of operation.
If your friend also has his radio set up the same way, then he too will be listening on the frequency that the repeater is transmitting, and sending on the frequency that the repeater is set up to receive.
So.... When you or your friend transmit, your signals don't need to reach each other directly. They only need to reach the repeater's antenna. Remember that the repeater is likely to be located in a wonderful place with a good "view" of the area. Perhaps on a mountain top, or up on a tall building, or up on a nice tall tower. In that case, the repeater will hear you, and key up its transmitter. It will repeat your signal on it's output frequency, and, since the repeater:
(a) is in that good location with a clear "view" of both you and your friend's locations
(b) has a good antenna
(c) might have more output power than your radio
You may very well be able to have a clear conversation even though neither one of you could receive each other "direct" or "simplex".
You and your friend's radios will only need to have good radio paths to the repeater location for your conversation to take place. This arrangement greatly increases the effective range you can have with various radios. It allows for conversations with low power handheld radios all over town, or the county, or the state for that matter. This allows for far more utility and fun to be had with your radios, and also makes for a safer RF environment since you can use very low power to get the job done. They're everywhere! Many communities and locations have repeaters which have been set up by the local ham clubs, or by individual hams. Most of these repeaters are "open", meaning that they are free to be used by any licensed ham who happens to be in the area.
This means that as you travel around the state or the whole country for that matter, you can strike up friendly conversations, get information and directions, or get help and contact the appropriate people in case of trouble or an emergency. There are lists of repeater frequencies available, so you can pre-program your radio for any trip you're planning.
- What else do they do with repeaters?
- Linked Systems
One thing is called a "linked system". This is where a number of different repeaters are connected together in a network such that when you transmit into the system from one location, you "bring up" the whole system. Your signals are bounced around from repeater to repeater so that folks all over the state might be able to engage in a conversation or roundtable discussion. There are several of these linked systems in Wyoming. This allows for effective emergency communications over long distances as well as for just plain conversation to take place.
- The Autopatch
Another handy feature that many repeaters have available is called an autopatch. An autopatch is an automatic telephone patch. What this does is allow the radio operator to make telephone calls from his or her radio. Most handhelds and mobile rigs have touch-tone keypads to allow for the generation of DTMF tones (you know, those funny tones used to dial your telephone). If the repeater has an autopatch, a radio user can "bring up the patch" by pressing a key or key sequence, then dial the phone number. This allows for even more communications capability from your trusty radio. This can be a great safety asset since a ham can call 911 or other emergency numbers to get help for themselves or for others wherever they happen to be in range of the repeater. It's also handy when you need to know if the family wants you to pick something up at the store while you're out, or you want to set up that all important lunch date with one of your friends :)
- Cross Band Operation
One more fun thing that can be done with a repeater is to set it up to allow an operator on one frequency band to communicate with people on a completely different band.
- VOIP interlinking
These days it's relatively easy to connect a radio to a PC with an internet connection. With appropriate software a user on an HT can 'work' a repater and access such an interconnect. This will allow that user to 'extend' the reange of his repeater to, well, essentially the ends of the world. There're several such systems to choose from. The 146.640 repater has access to the EchoLink system.
- Repeater etiquette
A whole new topic - on deserving it's own page