There is something that has been puzzling me for the last 17 years. In November of 1991, QST reviewed the Yaesu FT-990, which used a 13.8 vdc PA. Worst case measured 3rd order IMD was -38 dB, 5th order was -47 dB. This measurement was at 100 watts output. The review is available on ARRL's members-only web site.
ARRL had this comment, "It's refreshing to see that it's possible to make a 100-W MF/HF radio with low voltage finals AND such low-distortion transmitter performance". As far as I know, no ham 13.8 volt radio has even come close to this TX IMD performance ever since. Looking at the 990 PA, there's a 2sc2166 predriver, a pair of 2sc3133 drivers, and a pair of 2sc2879 finals, all npn transistors, nothing exotic. So what was Yaesu's secret, and why hasn't anyone else even come close? Dave Hachadorian, K6LL Yuma, AZ . _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
