From: Garey Barrell 
Subject: Re: [drakelist] Re: Claas C operation of 6jb6 finals for CW


Garey Barrell  made an utterence to the drakelist gang
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Ron -

Wayne's suggestion to "turn the bias to where the plate meter just 
barely moves" doesn't result in Class C operation.   True Class C 
operation require the grid be biased "several times cutoff voltage".  
The only "benefit" with this setting is the reduction in "idling 
current" between elements of CW.  There is no real gain in the "class 
efficiency" of the stage.   It DOES however definitely move the 
operating point of the final tubes out of the linear range which will 
certainly mess up a SSB signal!  :-)

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
http://hr99.home.mindspring.com/R-4C_Servicez/>



Ron Wagner wrote:

>
> Ron Wagner  made an utterence to the drakelist gang
> ----------------------------------------------------------------------
> The bias voltage is used in other places on the rig besides just the 
> finals.  That said, have a look at the "drake mods" article
written by 
> VE3EFJ  http://www.dproducts.be/drake_museum/Drakemods.htm  select the 
> PDF version and look for bias. The 5 or so hit will be the CW discussion.
>
> He discusses backing down the bias provided that you are only running 
> CW. Keep in mind that the 6JB6s are a small linear amp, and adjusting 
> then out of linear will effect you CW note.  Might get the FCC looking 
> your way, or at least a few fellow ham unhappy with your key clicks.
>
> 73,
> Ron
>
> On Sun, 13 Feb 2005, F3WT wrote:
>
>> I run only CW and would like to bias for class C operation  those 
>> finals as
>> I did once for my home - made CW Xmter which has a couple of  807's.
>
>
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