[Elecraft] QRO

[Lou Laderman]

Isn't "conventional wisdom" that tube-based amplifiers are inherently
more rugged and forgiving that transistor amplifiers, easier to work on
or repair in the field, and that tube amps are the "way to go?" 
Has that changed, and other than price alone, why should I consider the
new Elecraft amp over a tube design featuring auto tuning such as the
Acom or the Alpha (older 87A or the new 9500)?
Lou, W0FK

"Vic, K2VCO wrote:
Tube amplifiers are expensive because high power components (HV variable
capacitors, high power bandswitches, power transformers, tubes, sockets,
etc.) are expensive. In addition, although the basic circuit is quite
simple, ancillary circuits to protect the expensive parts and provide
functionality like QSK and automatic tuning are needed. Finally, the
enclosure is large and must be well-constructed to be RF tight. A
homebrewer can build an amplifier relatively cheaply by using surplus
Russian tubes and scrounging parts. But you need to know what you're
doing, since mistakes can be fatal.

Transistor amplifiers are expensive because they are more complex. A KW
amplifier may have 8 power transistors, and the protective circuitry may
be more complicated than that for a tube amplifier. If you know that you
will be driving a 50 ohm load, automatic tuning is simple; just switch
in the appropriate lowpass filter for each band. However, transistor
amps are unhappy with even a low-to-moderate SWR, so a built-in antenna
tuner is really needed.
--
73,
Vic, K2VCO
Fresno CA"