OT. Antenna tester

I fix center pivot irrigation systems and am looking for an easier way to diagnose potential problems. The pivots are wire guided corner systems. A picture here:

OR:

The corner arm follows a buried wire and swings out in the corners of a field picking up additional acres that a regular circle pivot will miss. The antennas I want to test are mounted like this below the black tower box.

OR

The far left one angled down steers in forward, the far right one angled down in reverse. The horizontally mounted one is the safety/reference. It's helps with the steering and shuts the system down if the machine gets off the wire. We have to remove them to test them now. We energize the transmitter, aka oscillator, for the buried wire then set a new antenna directly over and perpendicular to the guide wire. We remove the suspect antenna and put it in the exact place as the new one and compare readings. Typical readings using our Fluke meters with a dummy load are 20 mv or so. Link to picture of antenna: I'd like to be able to test the antennas in place and without having to energize the buried wire transmitter. The transmitters are powered by 120 vac. Energizing the transmitters sometimes requires starting a diesel engine that powers a three phase generator. That can be a problem in cold weather and just getting to them in snow can be an issue. My idea was to use 12 volts from an accessory outlet on an atv. I'd make some sort of a wand to hold against the antennas that would energize the antenna so I could take a reading similar to what I see normally. The antennas run at 833, 1000, or 1200 hz. I found this gizmo and thought it might be useful: My idea is to put three of these gizzies in some sort of box and set each one to one of the three frequencies. Put three outlets on the box then plug the wand into whichever one matches the antennas I want to test. Is this at all workable? Is there something better, maybe something ready made for the job?

Thanks