Placed on high locations, a repeater is a receiver/transmitter combination, simultaneously retransmitting received signals. By doing this, two stations can communicate that might not be able to do so via a direct path.
To enable simultaneous listening and transmitting, repeaters employ two frequencies, with the disparity between them termed the offset. Without this offset, the repeater would only hear its own transmissions, rendering it unable to pick up external signals
Despite the presence of the offset, the proximity of the two frequencies necessitates additional isolation measures to safeguard the repeater receiver from overload. This isolation is accomplished by installing a device known as a duplexer, or in some cases, cavities are employed in both the receiver and transmitter paths.
In the 2-meter band, the offset typically spans 600 kilohertz. Conversely, on the 70cm band, the frequency offset generally extends to 5 megahertz due to its broader bandwidth compared to the 2-meter band, allowing for a wider split. Additionally, the use of a duplexer or cavities can enhance isolation, ensuring optimal repeater performance.
In the 2-meter band, repeaters with an output frequency below 147 MHz typically utilise a negative 600 kHz offset, while those above 147 MHz employ a positive 600 kHz frequency.
Example
- VK3RML
- You listen on 146.700Mhz
- You transmit on 146.100Mhz
- This repeater therefore has a minus offset of 600Khz
Example
- VK3RMM
- You listen on 147.250Mhz
- You transmit on 147.750Mhz
- This repeater therefore has a plus offset of 600Khz
Modern amateur radios usually have the off set programmed into them and all you need to do is set the + or - shift and the radio will do the rest.
There are exceptions to the offset rule so check local repeater listings. Check our repeaters and repeater book web site.
How do you call someone on a repeater?
Always listen first to make sure someone else isn't using the repeater. If there is no traffic you can put out a general call by saying VK3XXX listening on VK3RMM. If someone is listening they may reply to your call and you can begin a conversation.
To call a particular person just say VK3AAA this is VK3XXX are you about John? If John VK3AAA is available he will answer you and you can begin the conversation.
Repeater Etiquette
As previously stated ALWAYS LISTEN first before you transmit. It's fine to join a conversation just wait for a break in transmission and then announce your callsign. The next person to transmit will acknowledge you and invite you to join in.
If you are on a particularly busy repeater its a good idea to move to a simplex frequency if you are in range of the other station. This allows other stations without a direct path to use the repeater.
Remember to wait until the repeater has reset its timer, otherwise your turn short will be cut short, then leave a couple of seconds before commencing your transmission. This delay allows other amateurs to put out a quick call or announce emergency traffic.
There is no need to use your callsign on each over as the regulations only require you to identify with your call sign every 10 minutes. It is good practice to identify with your callsign when you have finished your conversation.
Doubling
If you are in a round table discussion using a repeater to avoid 'doubling' (two or more stations talking at the same time) make sure at the end of your over to hand it to the next operator.
Example: VK3AAA to take it this is VK3XXX. If you don't do this it will end up in total confusion as to whose turn it is.
Repeater Timers
Most repeaters have an inbuilt 3 minute timer and will shut down after this time. This is so that everyone gets a fair go using the repeater.
Make sure that the repeater resets the timer at the end of an over. This is done by letting the repeater transmitter to drop out before you start talking. On some repeaters you may hear a courtesy tone that indicates the repeater timer has reset and there is no need to wait for the repeater transmitter to drop out.
If you jump in without letting the repeater reset your over is limited to three minutes minus the duration of the previous over. If the repeater times out it will not reset until all traffic using it has stopped. You will also occasionally hear the repeater identify itself using morse code or by spoken word.
CTCSS Tones
Some repeaters in high noise areas have tones access enabled on them to prevent false triggering of the repeater. The tones are sub audible and you must have the tone enabled on your transmitter to access these repeaters.
Most repeaters in Victoria that have tone enabled use the standard 91.5 Hz tone. Check the callbook or enquire with your local club to see if you need to program a tone on your radio for the local repeater.
Some dual mode repeaters (Analogue and Digital) have tone access on both the transmit and receiver. This is done so that your analogue radio needs the receive tone to open the squelch and you don't hear the repeater when it is operating in digital mode.
Most modern amateur radios have the CTCSS option installed in them.
DTMF Tones
These tones are the same as used on your telephone. These are generally used to access certain functions on a repeater. This could be getting the repeater to respond with local temperature, time of day or perhaps battery condition. Not all repeaters have this function.
The more common application is for accessing IRLP (Internet Repeater Linking Project) enabled repeaters. Using DTMF tones you can link to another IRLP enabled repeater either here in Australia or around the world.
Signal Reports
The only valid signal report that can be given on a repeater is to indicate that incoming signal you are listening to is fully quietened. This means that there is no back ground noise on the persons signal can be heard. Remember that the signal strength on your radio is not an indication of the other persons signal but is an reading of how well you can hear the repeaters output.
Some common Q Codes heard on repeaters
- QTH - What is your location, or my location is
- QSL - I understand or can you acknowledge receipt
- QSY - I am changing frequency to, or can you change frequency to
- QRZ - Who is calling me
- QRT - I am finished transmitting or please stop transmitting
- QSO - Can you communicate Or I can communicate
- QRM - I am experiencing interference (man made)
- QRN - I am experiencing interference (natural)