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The schematic or, click here for it in PDF format (12kb). A PTT-controlled relay switches the antenna between the transmitter output and the receive-only RX ANT IN input of an FT1000MP transceiver.
Two units, for the Run & Mult stations. The relays are Jennings RJ1A vacuum relays. The separated receiver input is protected by back-to-back PIN diodes.
The cable connections. There is a diode-or circuit on the PTT circuit so it can be fed to another piece of equipment if required.
The pull-in time, between applying 24V to the coil and the Tx connecting to the linear. 2.23ms and 2.33ms were measured on two relays.
The break time, between removing 24V and the Tx disconnecting from the linear. 1.59ms and 2.82ms were measured on two relays.
Two signal generators were combined to measure the intermodulation products produced by the PIN diodes. Carriers of 14.110 & 14.190 MHz, both at 0dBm, were applied. This picture shows the spectrum without the PIN diodes.
The spectrum with back-to-back PIN diodes shunting the input to the spectrum analyser. The 3rd-order intermodulation products are -57.8dB down on each carrier.