Re: Pre driver and driver transistors


Again, you-all might do a little research by reading all of the posts from about a year and a half ago.  No sense reinventing the wheel.  There were several people working this issue… redesigning output transformers, changing the feedback components on the finals (oh yes, those parts are frequency dependent), adding another drive state, changing bypassing). As I recall, the group consisted of a DL, a VK, a K9, and another euro station… some of these people have since left the group.  You might reread all of that dialogue and weigh that in with  Allison’s ever-present posts.



From: [] On Behalf Of Gérard
Sent: Wednesday, June 3, 2020 11:12 AM
Subject: Re: [BITX20] Pre driver and driver transistors




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.



Le mer. 3 juin 2020 à 17:32, ohwenzelph via <> a écrit :

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...
jer aa1of



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