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Remote Antenna Relay Selector
The circuit above is what I propose to use for remote relay
antenna selection. After discussion with Julius D. Jones, the owner of
W2IHY Technologies, who kindly related how he achieved 70 dB
isolation through the use of two relays instead of a single relay that
only provides 40 db of isolation, I have decided to construct a remote
coax selector box myself.
I have designed a circuit that uses a single 3-pole DT relay that
should provide the requisite isolation and protection from high
voltage flash-over by placing two open contacts in the path of the
unused portion of the circuit. (Drawing above) This permits me to
incorporate metal-oxide varistors (MOVs), and other surge protection,
on the relay control lines to mitigate potentially harmful surge
currents that may be induced into them, and place capacitors and 1KV
PIV diodes reverse biased across the relay coils to dampen any
inductive spikes that may be generated upon coil de-energisation.
Constructing a remote relay coax selector also permits me to
incorporate a weatherproof enclosure, and provides the pride and
satisfaction afforded by designing and constructing.
Below are some photographs taken during the construction
of the remote antenna relay selector system.
The
Alpha Digital Antenna Selector (DAS) controls the remote antenna
selection relays. The
Alpha 78A linear amplifier automatically tunes to the transceiver VFO
transmit frequency, and selects the antenna that has been previously
programmed for that frequency band. The DAS may also be controlled
directly by
TRX-Manager either locally or remotely. |
