[Amps] My conclusion: Re: Low SWR Input Amps

w3hvq w3hvq at frontiernet.net
Wed Nov 3 14:37:27 PDT 2010


Friends,
    The three responses received within a few hours after my posting are greatly appreciated.  I have decided to scrap the idea of "no input tuning" and immediately pursue using a switched-in tapped, tuned circuit for each band.  I figure on initially setting the tap at the 60 percent point from the bottom end of each coil (in the parallel LC circuit).   I will adjust Q by adjusting the LC ratio so that it will work OK over each band.   I was especially interested in the amps reflector response number 9 which even included a suitable rule-of-thumb input resistor of 90 ohms for realistic 4-1000 tests without applying any of the tube's voltages.   I'm sorry that I do not have time to supply any further information to you guys, as I've already put my name in with about 90 others who expect to be working the SSCW contest this weekend.
    I can say that I originally built this amplifier in the days when all transceivers were of the tube type.  That is, all had output tuning and loading controls that allowed amplifier's SWR of 2 to 4 to be matched OK.  There was no consideration ever given to impedance matching within the amplifier.
    While I will eventually install tuned circuits for all six HF bands,  I may omit 160m and 10m for this weekend's activity.  Go PVRC!
Thanks my buddies,
John, W8OHT
  
  


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