I finally decided to clean up the antenna switching system this summer also. I was interested in protecting against hot switching, and also getting rid of the little knobs from those MFJ control boxes. I looked at some of the commercially available boxes that had ptt protection, but they also did lots of other stuff and were way too expensive for the quantity I would need (10 boxes). So I inquired on a couple reflectors to see if anyone had a simpler solution, preferably one that didn't need a bunch of integrated circuits that could generate noise or need filtering from RF, no micro processors to program, just a simple relay system would do. I was told it couldn't be done with just relays, and of course then had to prove that it could be done. After prototyping a simple relay circuit I found N5QQ who was interested in building a set of them for me. After some negotiations we settled on a design and housing and he went off and built me 10 boxes. There were only some simple changes to the original design I came up with due to differences in latching and unlatching speeds of the relays that he used. The boxes were delivered in August and only took a few hours to wire in and replace the existing switches for transmit and Beverage antennas. So no more hot switching worries now, much bigger and easier to read labels, and also no more guessing which Beverage you are on because the switch knobs were loose.
The basic schematic.
The insides with the cables hooked up. The diode matrix is under the wires where they come in. All connections are to those wire clamp blocks on the left side.
The 40m TX antenna one sitting on the new TIC Ring controller.
20m box closeup showing label. I went for a box that was probably a bit taller than needed to be sure there was plenty of room for a good label.
