TRANSMIT-RECEIVE ["T-R"] SWITCHING CONSIDERATIONS:
T-R switching of a single antenna with a 2 Meter transceiver and the PA1 RF amplifier may be accomplished in any of these ways:
•1. Internal connections to your transceiver, making use of its built-in T-R switching circuit or relay.
•2. External T-R relay controlled by transceiver microphone switch or relay line.
•3. RF-activated T-R switch such as the Ramsey RFS-1 kit.
•4. PIN-diode T-R switching.
You have to make your own decision about whether to tie into any of the internal circuitry of your transceiver. It depends on how comfortable you are in doing so, how dependent you are on factory or professional service, and the policy of the service center on modified equipment.
We developed the RFS-1, T-R relay kit exactly for those situations where PA1 operation is needed but there is reluctance to make additional connections in and out of a costly hand-held transceiver. The RFS-1 kit is very economically priced and includes a heavy-duty 12-volt relay. Sorry, but we cannot make the PC board or individual parts available separately from the entire RFS-1 kit.
The use of PIN diodes for T-R switching is discussed amply in recent editions of the ARRL Handbook and in ham radio magazine articles. A practical circuit requires two suitable PIN-diodes, RF chokes, bias supply and either a quarter- wave line or tuned circuit for receiver isolation.
PA-1 • 12
