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[AMPS] Splatter

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Subject: [AMPS] Splatter
From: (Rich Measures)
Date: Sat, 7 Jun 97 20:56:34 -0700
>>> Amen to that,  Carl.  3mA to 10mA of grid current is bad news for a 
>>> 4CX10000A.   For a pair of 4CX800As, its downtown nutsville.  OTOH, there 
>>> is no FCC spec. for spurious feculence/splatter INSIDE the ham bands.   
>>> Rich---
>Hi guys,
>... ... As a user of an ETO91b which uses a pair of 4CX800A/GU-74b's can 
>tell me what the grid current is when the red 'grid max' light
>illuminates.  Is it in the 3-10mA range that is 'nutsville'.  I'd hate
>to damage the tubes as I believe they are quite delicate in the grid
>current area, even if they are cheaper than 3CX800's.

The "bad news" is not damage to the tubes' 2w-rated grids, Andrew.  The 
"bad news" is rotten splatter.  In a grid-driven amplifier, a small 
amount of grid current means a large amount of intermodulation 
 According to Svetlana's spec. sheet, 3rd order IMD from a grid-driven 
4CX800A is a respectable minus 30db with ZERO grid current.  However, 
with 3 to 10 mA of grid current, substantively higher distortion is a 

R. L. Measures, 805-386-3734, AG6K   

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