Operation with Antenna Change-Over Relays
The LT23S does not contain
its own antenna change-over relay. A
built-in antenna change-over relay would only make it harder to connect a
linear amplifier or a masthead (GaAs FET)
pre-amplifier. Instead, each of these options may be supported
with a pair of coaxial relays for each amplifier.
It is good practice to
install a high quality coaxial relay near the antenna (say in the roof space)
and to use a pair of coaxial cables. The
receive cable is connected to the 1296MHz in socket. The transmit cable is connected to the
1296MHz out socket.
One side of the coaxial
relay solenoid is connected to ground.
(The ground return is via the outer of the coaxial cable). The other side of the solenoid is connected to
the + Relais terminal with a single conductor wire.
On receive, the coaxial relay is energised, connecting the antenna to the input of the
LT23S. On transmit, the coaxial relay is not energised
connecting the antenna to the output of the LT23S.
Warning:
Switching the coaxial relay
induces a high voltage across the solenoid.
Make sure a diode (e.g. 1N4001) is connected across the solenoid. The
cathode (marked with a ring) is connected to the positive end of the solenoid.
p7
© GJ
Coyne & G Mussler
Dec-2003