I found the instruction manual to the Raytheon RA-250 transmitter (used both by KFGR and KPDQ) online. You can see photos and a schematic of the transmitter there. The RF final amplifier was a push-pull triode design (using the 810 tube) that had to be neutralized. I would imagine that this transmitter would have generated all sorts of nasty IQM and modulation splatter if the neutralization control were not set just right.
