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[Amps] How to read the 3-500Z spec sheet?

Subject: [Amps] How to read the 3-500Z spec sheet?
From: Bill Dzurilla <>
Date: Sat, 22 May 2010 07:39:40 -0700 (PDT)
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I'm looking at the spec sheet for the 3-500Z at

At the top of the second pages, it gives numbers for various parameters at 
different levels of high voltage (3000, 2500, 2000, and 1500).  Are these 
voltages at load or no-load?  And how do Single-Tone DC Plate Current and Peak 
Envelope Useful Output Power correlate with key down plate current and output?

The reason I ask is because I picked up a homebrew 6m amp with a single 3-500Z, 
which uses a power transformer from an SB-200.  Key down power output is 400w.  
Assuming the amp's meters are accurate, no-load plate voltage is 2300v, and 
plate voltage under full load is 1950v.  Plate current with no drive is 100ma 
and plate current with full drive is .52a.  About 40 watts of drive produces 
the full 400w out.  Further increases in drive, up to 100w, do not increase 

Judging from the spec sheet's 2000v table, my guess is that the amp is 
performing as well as it can with this power supply.  I know that a converted 
AL-80B with a single 3-500Z can produce 900w or so on 6m, but it has a 3000v 

Do you think it would be OK to run this amp at the full 400w in WSJT 
(continuous carrier) modes?

73, Bill NZ5N 

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