I built this control box to help with using two radios in contests. The box controls my radio's keying, audio switching, bandpass filter switching and antenna switching. A second control box lets me switch antennas between radios and switch the two radio's audio outputs to the headphones. I don't have yard space for more than one tower, so my antennas are all shared between the two radios.
The main criteria in designing the antenna switching configuration was to never switch an antenna to both radios at the same time. The LEDs give me immediate feedback (other than neither radio making crackling, frying sounds when I key the other) that this criteria is being met.
Some background on my thinking about the switching protocol for the antennas may be helpful. My A3S tribander at 70 feet is my workhorse antenna for 10-20m. I need to have it available to either radio. Whe one radio is on the Upper tribander, the other radio is or can be on the 10-20m vertical in the backyard. Not the greatest antenna, but for spotting or S&P purposes, it does the job.
When the lower bands are open, one radio can be on either of the 40m antennas (the 40m add-on on the 70' A3S or on the 40m inverted vee), while the other radio can be on the tribander(s), the 80m half sloper or the 160m inverted L.
A rotary switch in the lower righthand corner of the front panel lets me switch the radio connected to the tribander to the upper A3S or the lower A3 (at 40', fixed on the West Coast), or to both tribanders (to be heard on both coasts).
My 160m activity in a contest is minimal at best, where I'm generally always QRP). I decided that if 160m was active and I needed to move there, the triband beams would not be needed. So the tribanders and the 160m inverted L are A/B'ed in the relay box with a toggle switch.
I feed the audio output of both radios through the box to my headphones. The switch in the lower lefthand corner of the front panel switch radio 1 to both headphones, radio 1 in the right/radio 2 in the left headphones, or radio 2 in both headphones. I try to leave it in the both radio's mode to try to become more comfortable with the different 'hearing' I'm experiencing. It seems to be coming along, albeit very slowly. Even during Sprint, I was able to find a couple of new potential QSO's, but it took me so long to get there, they were into another QSO before I could make the first call. I'm learning, though.
Antenna switching is accomplished with a WX0B Array Solutions Six-Pak remote antenna switchbox. The switchbox is located in the garage where the VHF and HF antenna and switchbox and rotator control lines meet. The Six-Pak switchbox is very versatile. The three triband antennas (C3E, A3S, 12AVQ) are each fed to the 20, 15, and 10 meter antenna ports on the switchbox. The control lines to my antenna control box at the station desk allow me to switch radios/antennas in various combinations (Radio1 to A3S/Radio2 to C3E; Radio1 to A3S/C3E/Radio2 to 12AVQ, etc.) It has been through a number of contests and has performed very well.
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KG5U's Two Radio Control Box / firstname.lastname@example.org