Repeaters (8b1)

 

In this section we look at why we have repeaters, how they work, and how to use them.

 

What is a Repeater

 

We saw in the propagation section, at v.h.f. and u.h.f. hills cause “shadows”, so that a signal transmitted close to one side of a hill will not be heard close to the other side of a hill. 

 

If however we install a repeater at the top of the hill, which receives signals from either side of the hill and re-transmits them, then we can communicate from one side of the hill to other using the repeater.

 

The repeater increases the range of a mobile or portable station.

 

When the signal is re-transmitted by the repeater, the transmission is on a slightly different frequency in order to stop the transmission being picked up by the repeaters receiver.  This difference between the transmitter and the receiver frequency is called the repeaters offset.  It means that when you transmit to a repeater, you need to use a different frequency to when you listen.  The difference is usually minus 600 kHz on the 145 MHz (2m) band, and plus 1.6MHz on the 433 MHz (70cm) band.  You transmit 600 kHz lower than you receive on 145 MHz when using a repeater.  

How to Use a Repeater

 

·          Set the correct offset frequency.

 

·          Then to ‘wake up ‘ the repeater you transmit a tone burst or a special CTCSS tone.

 

·          You then make your contact with another station through the repeater. 

 

·          Keep your ‘overs’ short, as repeaters often have a time-out (shut down) after a period of between 1 and 2 minutes.

 

·          When you finish your over, you must wait for the repeater to transmit the letter ‘K’ in morse (Dah dit Dah), so that it resets its timer.

 

·          Remember your licence conditions don’t change when you use a repeater. 

 

 

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