In a message dated 9/12/07 11:12:05 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> the Heathkit SB-200 has several > modifications that can be made to it, one of which is the reduction of drive > power to excite it. What is modified to do this? > > Does anybody have any idea what the lowest power required to excite an > SB-200 amp is? > I presume you meant "what the lowest power required to excite an SB-200 amp to full rated output is" The SB-200 uses a pair of 572B triodes in grounded-grid. The data sheets list the 572B as needing 50 watts of drive in that service, so a pair will need 100 watts of RF to drive them. > Without mods, it is around 100 watts, but I use to have one with the > reduced > drive mods, and I drove it with 30 to 50 watts for around 300 watts out. The tube ratings (for a pair) say that 100 W of drive will give 600 W output, so 50 W of drive would give 300 W output. I don't see what could be modified to reduce the drive requirement for full output, except perhaps changing to grounded-cathode operation instead of grounded grid. But such a mod would be extensive, requiring neutralization and other changes. I > > never tried testing the lower end with that mod. Though. > > Bottom line is: if an SB-200 had the reduced drive mod, could a QRP K2 at > 10 to 15 watts with an amp key interface safely/adequately drive an SB-200 > to say, 50 to 60 watts out? > Since the SB-200 is a linear amplifier, I don't see why not. Of course it's using a sledgehammer to drive a 3d finishing nail.... The problem is, how do you tune up the SB-200 with such low drive power? --- I'm curious to know what is changed by the "low drive mod" for the SB-200. Thanks 73 de Jim, N2EY ************************************** See what's new at http://www.aol.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
