ADVANCED LESSON 64logomidi2.gif

             
LEARNING  OBJECTIVES and NOTES
Operating Practices and Procedures - Repeaters
8b.1 Recall the purpose and operation of repeaters and the correct procedures in using them. E.g. offsets on 144 and 433MHz; time-out and reset tone; voice procedures.

Repeaters are designed to extend the range of communications, particularly for mobile stations. For example in a hilly area two stations in adjacent valleys with a high ridge between them would not be able to make contact. By putting a repeater on the ridge, the repeater will be able to relay the information to and from each station.
A repeater is normally located on a high point with a good coverage of the local area.
At the repeater site there is a receiver tuned to the input frequency and a transmitter tuned to the output frequency. The output from the receiver is connected to the input to the transmitter. There is also a logic board to control the system.
The spacing between input and output depends on the band. On 2m it is 600kHz (The repeater transmits on a frequency 600 kHz higher than its receive frequency) and on 70cm it is 1.6MHz (The repeater transmits on a frequency 1.6MHz lower than its receive frequency)

For example the GB3AS repeater has an output on 145.600 MHz and an input on 145.000MHz.
GB3DV has an output on 433.025MHz and an input on 434.625MHz.

To limit the time for a transmission, many repeaters are fitted with time-out logic. These start when the repeater is accessed and after a set time - say 2mins- the transmitter is turned off and has to be re-accessed.

When not in use repeaters are silent. They are turned on when a carrier and a reset tone (1750Hz) and sometimes speech are received. Repeaters are now turning over to use a CTCSS tone which is a low frequency tone which is on throughout the transmission. The are CTCSS tones vary from region to region. CTCSS stands for Continuous Tone-Coded Squelch System. The 1750Hz tone is being phased out of use.

The procedure for a repeater contact is as follows
  • Tune to the repeater transmitter frequency, make sure the repeater shift is set, set the appropriate tone.
  • Listen to check if the repeater is in use
  • If it is quiet check that you can access it by pressing the transmit button and saying something like "This is G3ZPD testing for access through GB3AS". Release the PTT and if you have been successful you should here the repeaters carrier turn on and get some form of response such as a pip. If no one replies the repeater will close down and go back to listening
  • You can then try calling "This is G3ZPD listening on GB3AS for any calls" A reply would be something like "Calling G3ZPD,CTCSS Tone (Hz) how do you copy? This is G3ZZZ/M". You can then have a QSO, but remember if your over is too long you will time out. Often the repeater closes down for a period of time. It then starts to listen again for a carrier and access tone.
  • In quiet periods a repeater will send its callsign, location and CTCSS tone at regular intervals.
If you are in a busy area keep the overs short and leave a pause for any breakers between overs. priority should be given to mobile stations.





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CTCSS Tone
 CTCSS letter (sent in CW by repeater)
67.0 A (.-)
71.9 B (-...)
77.0 C (-.-.)
82.5 D (-..)
88.5 E (.)
94.8 F (..-.)
103.5 G (--.)
110.9 H (....)
118.8 J (.---)

You do not need to learn this!