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Cathode modulated G-G 2x813 linear (3 replies)
The 813's are monsters! There are methods to 'linearise' the envelope by using negative feedback to the modulating amplifier. Sniffing and detecting the O/P envelope and applying this is anti-phase somewhere within the modulator, certainly used in broadcast. I suspect the O/P stage could be run in class 'C'.
Otherwise it's 'anode and screen'! Loads of power .. ;)
Back when I had hair and was at skool no money for a proper a mod transformer,so a 12at7 tetrode valve b9a base ant a 12at7 af amplifier and a few bits this went to the screen of the `6-40a or 4cx250b if you were rich! .this contraption was called Series gate modulation and apeared in technical topic in the bulletin(radcom now).A few people used it also without our knowledge Continental and Marconi.but time makes you forget SSB appeared and the rest is history.But it would be nice to get the RCA Tubes going again on AM. Jon 73`s
THE AF preamp was a 12axt and 6c4 mic amp.sorry jon
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as I wish to join in on topband on the AM nets I wondered if I could cathode modulate the amp as its in g-g.Years ago I ran series gate mod to a qqvo6-40a double tetrode on 2mtrs using a 12at7 I think.
MY FLEX 3K can do AM but i want to see valves do it.
probable the bias would have to be switched between ab1 and C IF A AB1 amp is not the done thing ,could I use a mosfet feeding the center tap of heater xfmr.
one for the more senior members one springs to mind may know.
Regards and 73`s Jon`8CCL