TX Rx Switching

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As do many other collectors of old radios, I was faced with the dilemma of how to switch between several receivers and several transmitters. I found the Ameritron RCS-10 almost ideal for a four transmitter-four receiver setup.

I designed the RCS-10 many years ago while engineering for Ameritron. The Ameritron RCS-10 is an eight-position switch that uses BCD control signals. The simple basic control head has a diode matrix to output BCD from 000 though 111 to select up to eight antenna ports. The RCS-10 has the unique feature that only one port can be selected at any one time, making it impossible to cross-connect equipment on any ports.

  A B C
1 0 0 0
2 1 0 0
3 0 1 0
4 1 1 0
5 0 0 1
6 1 0 1
7 0 1 1
8 1 1 1

Also notice that ports 1 through 4 are selected when line C is low, while ports 5 through 8 are selected when C is high.

By connecting receivers to ports 1-4, and transmitters to ports 5-8, the RCS-10 can be used as an antenna transfer relay and radio selector. Matching pairs of equipmment are connected to the following ports:

Port Rig
1 RX1
2 RX2
3 RX3
4 RX4
5 TX1
6 TX2
7 TX3
8 TX4

BCD A and B select the radio pair, while BCD C becomes the T/R (transmit-receive) relay. Whenever C is high, a transmitter is connected to the antenna.

This leads to the question, what if I want to mix equipment? 

My solution to that is to have two BCD control boxes that are activated, one for the receivers and one for the transmitters. A simple power transfer relay switches between the control boxes.

In this case any number of transmitters and any number of receivers can be used, so long as the total used is 8 pieces or less. I current use this system with five receivers and three transmitters. Dual switch control boxes are used, with output wiring paralleled to a single relay box.

The T/R relay control comes from a 12 volt SPDT relay that applies power to the receiver selector box. When a transmitter comes on, I have a 120 volt sensing circuit that activates the transmitter relays.