Remote Coaxial Antenna Switch

Many years ago I built a remote antenna switch that allowed feeding up to 4 antennas from the same feedline. The feedline also was used for the control signal, so no additional wires were needed.

It was a very simple circuit. The switch box at the top of the tower contained 5 coax connectors, two DPDT relays, two diodes, an RF choke and a couple capacitors. The control box in the shack contained 2 coax connectors, a 60-Hz power transformer, a 4-position switch, an RF choke, two diodes and a couple capacitors. In the diagram below, the relays are shown in the un-energized position.

Schematic of remote antenna switch

The electrolytic capacitors in the switch box may not be needed, depending on the relays. I believe I used 0.1 uF for the coupling and bypass capacitors and something like 22 or 47 uH for the RF chokes. (For VHF, smaller chokes might be required to avoid in-band resonances.) The diodes are garden-variety 1N4xxx-series power supply rectifiers. The transformer was chosen to provide the correct relay voltage. You may need to add resistors in series with the relay coils to fine-tune the voltage.

Jim K5LAD has posted a complete construction article on his personal web site.

- N1AL 6/8/2011

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