ERG - Repeater Cavities
Sets of cavities are used on all ERG repeaters to perform the diplexing function necessary to enable simultaneous receive and retransmit on single aerials without self-desensing.
All FM systems now use professional high performance Procom/Telewave cavity sets. Each set has two banks each of three cavities - one bank on the transmit and one on the receive path. They are the single most expensive part of the repeaters.
Originally the repeaters used home made cavities. Those on GB3DA were replaced with the professional high performance Telewave design in 1993. A little later GB3ER moved to RB3 and a commercial Procom design was acquired. In Sept 1997 GB3ER was also upgraded to the Telewave design as the final step in eliminating its recurrent desense problems. The cavites are temperature compensated and are now largely maintenance free.
The later GB3ZP 23cm and GB3DB 6m repeaters used Procom/Telewave professional 6-cavity sets. In the 23cms case, this was believed to be the first example of professional cavities on a UK 23cms repeater. The format is similar to the 70cms set on GB3ER, whilst the 6m ones are a 6ft+ tall version of the GB3DA 2m design
Our D-Star system GB7ZP was acquired as a turnkey system and uses a more compact Procom Duplexer
GB3DB - The large 6m cavities are pictured on the Home Page of Murray G6JYB