Recently, a friend asked how I do antenna switching at my shack. Here’s how.
Basically, I use two antenna relay switches. The first is a remote coax switch, the Ameritron RCS-10. Shown at the top of the picture is the remote switch box in the shack. The weatherproof relay switching box is outside. I have it configured to switch between my two main antennas: a dipole and a beam. While it can control up to eight antennas, I am only switching two at present.
There are a number of benefits to using a remote coax switch. These include a common location for grounding and lightning protection, as well as a reduction in the number of cable runs. The drawback is that you can only use one external antenna at a time. This works okay for me.
The second relay switch is for routing the antenna inside the shack. The MFJ-4716 (lower picture) lets me switch the external antenna to one of two transceivers. It also lets me route the antenna to different receivers in the shack, or to the lab down the hall.
I also have a few more coax cables routed outside for other antennas, such as my magnetic loop. These do not run through the relay switches and are not shown in the diagram above.
Antenna Switching Coaxial Cables
For transmitting, I use LMR-400 coax. This includes the connections to the antennas, as well as between the relay boxes and to the two transceivers. This coax is good quality, low loss 50 ohm cable. For receiving only, I make do with RG-6 75 ohm coax, also used for cable television. This is cheaper and easier to route around the house. There is a slight impedance mismatch but that really does not matter for receiving.
Finally, position #4 on the inside switch, marked “Receivers”, is connected to an antenna multicoupler. A multicoupler allows you to distribute one antenna to many receivers. Mine has an internal amplifier to compensate for the loss when you split a signal to multiple receivers. An alternative is a simple cable television splitter. Remember, each “split” reduces the signal strength in half (3 dB). But the benefit is being able to listen with several receivers on the same antenna.
When not in use, turning these switches to the off position grounds the system. I have found relays to be more reliable than mechanical coax switching.