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[AMPS] Anode current vs cathode current...

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Subject: [AMPS] Anode current vs cathode current...
From: (Rich Measures)
Date: Tue, 3 Mar 98 05:43:49 -0800
>Hello all,      (... a question to Rich and others who care to chime in)
>>When measuring power out, it's important to measure anode current.  If 
>>the anode current is low,  input swr may be causing the problem.  If 
>>the load is other than 50 plus or minus j zero ohms, all power 
>>measurements are suspect.  
>Would there be a specific difference from the cathode current? 
>In particular,  circuits using AB1 vs AB2?
In AB1 grid-driven, the anode and cathode currents are pretty close 
because there is zero grid current, and the screen current is typically 
only about 3% of the anode current.  .  However, in AB2 cathode-driven 
using a directly-heated cathode type tube, grid current can be 
substantial, especially during lowered anode V operation.  Nevertheless, 
in a situation where the cathode current was metered and the anode 
current was not metered, by subtracting grid from cathode current, one 
could arrive at the anode current.  
>I'm just trying to understand if there is an specific advantage/reason
>for the mention of  anode vs cathode.
By measuring anode[plate] current, one can see if the tube is being 
driven to the max rating.  There is no max. cathode current rating to 
compare with, although there probably should be, Skip.  


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

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