Tony King - W4ZT wrote:
>
>Right, it may not, but if someone took the time to do it on whatever
>amps they had available, there would be SOME data that could be used as
>a yard stick for everyone that is interested in the question of tuned
>input or not.
Possibly this is because the pioneering work on the linearity of tube
amplifiers was done in the 1950s and even earlier. Spectrum analysers
were in their infancy, and IMD measurements were slow and difficult to
make.
The approach in those days was heavily based on mathematical analysis of
tube characteristic curves. It produced a deep fundamental
understanding, but there were far fewer IMD measurements than we would
expect today.
Today, even radio hams can have much better measuring equipment than the
guys who did the pioneering work. People are still building tube
amplifiers using the techniques and circuits that the old guys
developed, but nobody is doing basic research on tube amplifiers any
more. If anyone wants to apply modern test equipment to old questions,
like the effect of tuned input n IMD and efficiency, they'll probably
have to go back and do it themselves.
>Don't get me wrong, I agree with your statement below. I believe that
>it is much better to use a tuned input than not. The empirical
>knowledge indicates that one with a tuned input is easier to drive, has
>higher efficiency and is more neighbor friendly. BUT, there are plenty
>of old school Hams that still subscribe to the "you don't need a tuned
>input" theory and they are Elmers to a lot of people.
>
A much better group of Elmers would be the engineers from the Collins
company who literally 'wrote the books' on the whole topic of linear
amplifiers. Two books, in fact:
'Single Sideband Principles and Circuits' by E W Pappenfus, W B Bruene
and E O Schoenike (1964)
'Single Sideband Systems and Circuits' by W E Sabin and E O Schoenike
(1984).
These books are solid gold, so send out your spies to Amazon and eBay.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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