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Re: [Amps] Why does power output increase?

Subject: Re: [Amps] Why does power output increase?
From: Jim W7RY <>
Date: Sat, 4 Jun 2022 22:19:36 -0500
List-post: <>
*I'm curious Vic...*

*See below"*

On 6/4/2022 4:35 AM, Victor Rosenthal 4X6GP wrote:
This isn't a problem, just a phenomenon that I would like to understand.
I have a TL922. Mods include directly grounded grids. I also measured the filament voltage with my Fluke true RMS meter and put a small resistor in the primary of the filament transformer to provide exactly 5.0v in standby.
*Where did you measure this voltage. Best is to wrap a small wire around the tube pins, (all 3 of them) and measure the voltage at each tube.*

It has been running with the same genuine Eimac 3-500Zs in it for about 6 years.

So here is what happens: after a longish CW transmission, the power output INCREASES. On 20m, for example, it may go from 1200 to 1400 watts. When it cools, the power drops back.

I've noticed this with several wattmeters. I have observed no change in SWR when this happens (it's 1:1 thanks to a Johnson KW Matchbox).

It happens when the amp is driven with an Elecraft K3 and also a TS890s.

I'm interested in hearing theories about why this might occur.

*I cant add anything about what your seeing... Other than is the line voltage changing?

*73, Jim W7RY*

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