[NLRS] 432 Cavity Amp project (formerly know as "FQA Special ) - Final Report

[Ronald Bergantzel]

Hello All . Well , as I promised I am sharing how the old FAA Rockwell /Collins amplifiers from the K0FQA estate turned out . I finished the first unit after striping It from its original configuration  and performing a couple of simple modifications to the output cavity . My results are as follows : 1150 watts output with just under 50 watts drive from my FT991( output power was measured using a Bird 43 with a 2500 watt slug )  . The full technical specs are : 3100 vdc Plate voltage at 690ma Plate current( key down )  . Screen voltage was at 485vdc and aprox 5 ma ( key down ) , Grid voltage was -65vdc ( key down )  with a zero signal idling Plate current of  170 ma .  With the amplifier's configuration  the input and output cavities are tuned both at the same time , although at the 1150 watt power output the input SWR was 1.7:1  I think it can be improved upon some while still maintaining the 1100 watt plus output level ..... 
The low points of the project were the amount of time that was required to assemble the amp ( read - parts chasing ) . My next 432 amp will be a full legal limit version ( amp #2 )  with more cooling on the amp as well as going to a 7/16 DIN output connection . I have 4 of the cavities already stripped and modified and ready for a chassis with 4 more stripped from the original chassis awaiting for me to do the mod to the output cavity - I have salvaged the tube base pieces from the first cavity I disassembled for my reverse engineering  - and am curious what the RCA / Burle 4661 tetrode tube would perform like on 6 m ?? Also , with 20 some cavities , tubes , etc  I will probably build up a spare half wave cavity amp  for 144 like the GS35 workhorse  I currently use ( using in a grounded grid configuration) . 
Anyway , it's looking like I should be on 432 with some QRO during the contests - I need to complete an outside ( at the antenna ) box for my T/R relays and preamp  - maybe by next month for the last leg of the ARRL 50 - 1296 EME Contest : we will see .
Thanks to all of the NLRS gang  who helped me acquire these at Jon;s estate . 73 , Ron KA0RYT EN35ct