Re: Pre driver and driver transistors
toggle quoted messageShow quoted text
I have not yet asked myself the question to replace some 3904. For me the 2n2222 is an "old Go anywhere " transistor.It's work fine, but it is at least over 50 years old, I was already changing some in the years 70/80. We really should study the case.
Take a more "modern"? Ex :Bf 959 Bandwitch 1G against 300mo to a 2n2222.
But the change does not stop there. It may be necessary to adjust resistances emitters, base. See if anyone has already put transistors other than 2n2222. Take the µbitx version6 schematic and find an equivalent to the BFR93w.
Actually, I am not so concerned about the power out being equal across the bands. The concern is to have reasonably enough power out on the 10 meter end. And if 10 and 12 and 15 meters are open you don’t need very much power. At the 80/40 end I don’t mind if there is a lot more power, granted not QRP, but if summer thunderstorms are making a.a racket and you want to be heard, then it becomes a question of how do I cool those heat sinks. Why do they need to be equal? With increased power harmonics and spurs became more of a concern but my impression is that Farhan has fixed those. One can always try to optimise efficiency but that is less of a concern if not running on batteries or portable. I am still trying to understand the concept of IMD and the square root of negative one...
Join BITX20@groups.io to automatically receive all group messages.