[AMPS] Re: New G2DAF amplifier information

[measures]

>
>Rich says;
>
>>However with ordinary tetrodes,, grid current is clearly to be avoided 
>>unless one is either trying to clear away a wide swath during a contest, 
>>or operating on CB Channel 6.  . 
>
>What do you mean by 'an ordinary tetrode'? 

7580, 4-250A, 4CX1500A, 8169, 4-500A, 8171.  .

>  It seems strange to me that for
>many years, companies like Collins, Racal, Marconi, Standard Telephones,
>Brown Boveri, Thomson, Philips, Siemens etc have made tubes and transmitters
>to exacting professional specs (especially for ISB) and used AB2 operation.

Please name a (not G-G) Collins amplifier that used AB2 instead of AB1.  
. 
thanks

>But Rich says it doesn't  work. 

Rich says AB2 grid-driven works.  

> Just because Eimac only happen to list two
>tubes for negligible grid current (as opposed to none at all),  Rich says
>that Class AB2  produces splatter. Too much of a generalisation, Rich.

The constant current curves prove why this is generally the case.   The 
4-500A is an ordinary tetrode without the special dispenser cathode and 
low-intercept grid that distinguishes the 8660/4CX1500B.  .  Unlike the 
4CX1500B, the 4-500A's curves take a nasty turn when grid current is 
present.  Eimac recommends zero grid current for the 4-500A, 4CX1500A, 
8169, 8170, 8171, 8281, 8349 and 8973.  .  Surely, one gets a bit more 
peak anode current when the grid is positive, but the improvement on an 
S-meter would be unnoticed.  
>
later, Peter

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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