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

[Carl]

Which is why saying Deep Class B signifies a variation and has been used for 
ages.
Real old manuals used B/C

Not accurate for a purist but fine for real world use.

Carl
KM1H


----- Original Message ----- 
From: "Joe Subich, W4TV" <lists at subich.com>
To: <amps at contesting.com>
Sent: Sunday, January 17, 2016 9:09 AM
Subject: Re: [Amps] Need for bias switch (CW/SSB)


>
> > 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
>>
>>
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