> It is only necessary to reduce filament voltage by a few tenths of a volt, > which is not going to hurt anything. The first thing you should do is check and > monitor your power line voltage. Mine varies during the day by +5 volts! A > variac is the easiest way to control it but you have to be able to monitor the > filament voltage constantly for it to be of any value. Virtually all > broadcast transmitters back in the tube days had filament voltage variacs and a meter > to monitor the voltage, so it is important to know what is happening. Also > back in the good old days, these and other operating parameters had to be logged > every thrity minutes by FCC decree. A great after school job for us up and > coming hams.
I think the recent home-brewed modulator built (mostly) by WA5BXO does a pretty good job, at that. The meters, across the top are Ip Bias Voltage Filament Voltage http://w5omr.shacknet.nu/~w5omr/hamstuff/AM-Stuff/Titanic/modulator/ 73 = Best Regards, -Geoff/W5OMR
