[Elecraft] K3: 630m amplifiers

[Vic Rosenthal 4X6GP/K2VCO]

A CW amplifier can be designed to run class-C but to be keyed in such a 
way as to pass through the linear portion of the amplifying device's 
curve when a CW element is starting or ending, in order to preserve the 
shaping.

A simple example is the tube-type amplifier that has just enough fixed 
bias applied to allow a small amount of plate current to flow (class 
AB), with a grid resistor that provides the rest of the bias as a result 
of rectified grid current as the drive ramps up. At full power the tube 
is running class C with bias way beyond cutoff.

Good 1950's technology that can be made a little more sophisticated and 
applied today!

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 27 Jul 2015 07:32, Alan wrote:
>
>  > CW would be another mode that would not need a linear amp I think.
>
> No, CW requires a linear amplifier.  CW is not constant-amplitude - the
> amplitude changes every time you open or close the key.  A class-C
> amplifier would mess up the key shaping, causing key clicks.
>
> Any true FSK or MSK signal should not be bothered by a non-linear
> amplifier.  The only caveat I can think of is that the amplitude of an
> AFSK signal may have some ripple on it to the extent that the passband
> of the transmit crystal filter is not flat.  But I doubt that's a
> significant issue.
>
> Alan N1AL