my brain-input got out of control recently and I think that's why I failed to grasp what the dummy antennas on the SA-2's are for. Any hints what to do with them?
As it took time for the ancient electronics to react, and because sometimes it is important to follow strict emission control, the fastest way is just to transfer the high power from transmitter to the dummy load.... This is what I know....
Yes, exactly, you cannot simply switch off high voltage or heating for the vacuum tubes (especially with powerful ones as in transmitters). And they need time to heat up again, so it is the fastest and easiest solution to route the RF energy to a non-radiating load (dummy antennas).
With newer systems (Vega for example) it is possible to switch off high voltage for power tubes, but not so for the older systems.