[Amps] Need for bias switch (CW/SSB)

[Joe Subich, W4TV]

 > Instead it is in fairly Deep Class B in CW with a much lower
 > idle current which also works well in AM.

Class B is defined as a conduction angle of 180 degrees exactly -
therefor one can not be "fairly deep Class B".  It might be deep into
Class  AB2 - i.e., well beyond the point at which the tube starts to
draw grid current - but class B is a specific operating point not a
range like AB1, AB2 or C.

Class A = conduction angle 360 degrees
Class AB1 = conduction angle between 180 and 360, no grid current
Class AB2 = conduction angle between 180 and 360, with grid current
Class B = conduction angle 180 degrees
Class C = conduction angle less than 180 degrees

73,

    ... Joe, W4TV


On 1/13/2016 12:41 PM, Carl wrote:
> The FCC did it!
>
> Originally the rule was 1000W DC input  for any mode. Then it changed to
> 2000W PEP for SSB only so the plate transformer was tapped and a switch
> added,
>
> Some of those older amps have a pretty wimpy transformer and not suited
> for heavy duty CW use in the SSB position.
>
> The Ameritrons with that switch change the bias but it  never goes into
> Class C. Instead it is in fairly Deep Class B in CW with a much lower
> idle current which also works well in AM. The HV doesnt change.
>
> Carl
> KM1H
>
>