Fraser, If you have a 'scope handy, try cranking the power up to 100 watts on 160 and 80 and observing the CW envelope - if you see what looks like weak modulation on the top and bottom of the envelope pattern, you have a low frequency oscillation. If you do have that oscillation, the 'cure' has been discussed on this reflector - on the KPA100, put a 1K resistor across RFC3, and change R4 from 100k to 39k.
I have worked on KPA100s having this modulation problem, but never related it to current draw before, but it is worthy of investigation. 73, Don W3FPR > -----Original Message----- > > Thanks Geoff, the TR bias HV is 139V on RX. On TX at 70W out it's about > 118V on 160m and 80m. With power flat out it's 113V on 80m and 109V on > 160m. So I think that's ok. > > The voltage on U7B pin 5 and 6 is identical on 160m and 80m at > full power at > 675mV, so I think the PA bias current is behaving. > > G3VTT suggested the transformers, but they have the correct > number of turns, > including the po/swr sensor T4. > > Thanks / 73 Fraser G4BJM > > _______________________________________________ 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
