I think there were a number of reasons for eliminating input chokes and going
to capacitive input filters.
1. AM may have played a part but there were others.
2. The use of solid state rectifiers eliminated the need to protect the mercury
vapor rectifiers.
3. Cost savings is another. Besides the elemination of the input choke the use
of centertapped transformers
ceased as well. That also reduced the amount of iron and copper in the
amplifiers reducing cost, weight and size.
4. Linear amplifiers were not usually used for AM. Most AM transmitters used
plate modulators so they had lots of
iron anyway and cost was not an issue.
I personally prefer an input choke. It not only improves regulation but reduces
the need for oversized house wiring to the
to the amplifier. And reduces the capacitance required to achieve the ripple
reduction and regulation of the power supply.
The inductor's contribution to regulation is not the short term energy
storage, that is reduced only to the limit of the
high frequency cut off of the filter. A swinging choke really improves the
regulation because the inductance get lower at higher currents and the power
supply slides from a inductive input filter to one with a almost all capacitive
filter stepping up the plate voltage a bit.
Just some thoughts on the subject.
73
Bill wa4lav
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