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Richard Clark wrote:
Ultimately, it takes very little reading applied to the conventional designs found in Amateur class amplifiers to discover there is really very, very little modification of amplifier characteristics offered through negative feedback design (it costs too much). In fact, I would say none whatever - hence the heavy filtering at the outputs and the customers' universal acceptance of barely mediocre performance. It might be said that every transmitter owned by hams is a museum of 1930s performance. And for those who mistake the feedback of stabilization (barely found in those same cheap designs) - this is not negative feedback, it is compensation. It too has scant effect on tailoring (reducing/increasing) impedances. probably not "every transmitter", but certainly the vast majority of designs, particularly those for HF based on tubes in the ARRL handbook (and by extension, those sold to readers of the handbook). Cost *is* a factor. The Harris PWM modular transmitters are very cool, but beyond the means of most hams as a commercially manufactured item (in that, the NRE for a consumer mfr to get there would be prohibitively high) One should also not neglect that the hobby aspect of ham radio provides an incentive (for some) to preserve fine (or not so fine) examples of past radio art. No more unusual than steam train fans or classic auto collectors. There is a visceral satisfaction of seeing those glowing tubes with the plates changing color, notwithstanding that the RF performance, in objective terms, is horrid. As I am undoubtedly the only copy holder of this book in this group, access can be obtained through: I'll bet not..grin |
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