So, here it is. My dual channel antenna switch built and working in the lab. A project of synchronized switching relays.

Let’s count the relays as we go along. On the left are two 6:1 coax antenna switches. I bought these on eBay and then added case and connectors. A total of 12 DPDT relays, although I am only using four outputs at this time. As the receivers are dual channel, my code switches both boxes together.

Upper center is my main antenna switch. It contains eight relays for switching four antennas to two channels. My friend Jim VE6JF designed and built this switch using the same Songle SPDT relays used on the Arduino modules.

To the right is the medium wave bandstop filter. Each channel contains a relay to switch in a Distill AM filter module when I want to reduce local AM signals. Over on the far right is the AAA-1C control box for the loop array. There are 2 remote relays on amplifier boards outside used for switching multiple loops and modes.

Finally, shown in the lower center are the 16 control relays in two banks, opto-isolated from the Arduino microcontroller. And, a ton of wiring, mostly salvaged 24 gauge pairs from old Ethernet cables.

That, my friends, is a total of 40 relays allowing switching of multiple antennas to multiple dual channel receivers. Whew!

Synchronized Switching Relays Current Drain

Now, 40 relays can draw about 2.5 amps, each around 60 milliamps when activated. But, fear not. My relays are both 5 and 12 volt units, so they run off two different power supplies.

Also, with this design, no more than 24 relays can be active at any one time, usually less than 20. Both power supplies can handle the load. In some cases, I used the normally closed connections to save activating a relay. For example, the antenna power for the loops is normally on. Later, I plan to add a circuit to switch off the amplifiers when transmitting.

With this many relays, I did careful and well documented wiring diagrams for posterity.