[Amps] cw bias

[bob finger]

Vic:  1970's and 1980's HF amp designs published by ARRL often included 
switched zener bias for class ab and c.  What was described by W2RU I 
suspect is an adaptation of these designs.  I have used the same 27 volt 
zener with pairs of 3-500;s operating on cw.  Keeps the tubes cut off 
nicely.  One of course must not forget to switch it back for ssb, which 
I assume is why it has never been implemented commercially.  A look at 
the amp designs on arrl's web site will provide much food for thought.  
73 bob de w9ge

Vic Rosenthal wrote:

> W2RU - Bud Hippisley wrote:
>
>> 3.  I operate 99% CW, and have added a 25 - 28 volt (50 watt!) Zener in
>> series with the stock 5.1 volt operating bias Zener when I am on CW.  I
>> originally did this because I run full break-in on CW, and use an 
>> electronic
>> TR switch on the output of the amplifier, so I needed to cut off all 
>> plate
>> current to eliminate "hash" in the receiver.  Secondary benefits of 
>> this are
>> that I have no power dissipated in key-up idling current and my key-down
>> efficiency is probably slightly higher than it would be with the 
>> stock class
>> B biasing.  
>
>
> I am also primarily a CW operator and would be interested in hearing 
> about any others who have optimized amplifiers for CW.  I've always 
> felt that it's a shame to waste power by biasing CW amplifiers for 
> minimum IMD!
>