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[CQ-Contest] More on "baby ur radio"

To: Contest Internet <>, "" <>, "" <>
Subject: [CQ-Contest] More on "baby ur radio"
From: Charles H <>
Date: Fri, 18 Dec 2015 00:59:04 +0000
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On this reflector, I have poo-pooed the idea of baby-ing your radio especially 
by turning it off often, lowering xmit power, etc.
However, I read that with ordinary tubes, the chemistry of the cathodes and 
filaments are affected by life-of-use, so that tubes do "wear out" with use.  
Tubes can be rated in terms of "hours of use" with the type in a KWM-2 rated at 
around 2,000 hours of useful function.  Thorium in the chemical make-up of the 
metal parts in a tube, maybe a metal or ceramic tube (usually added to higher 
power tubes) can extend tube life to about 100,000 hours.

The conclusion is that "hours of use" of course do matter for hams intending to 
use their tube-type radios for thousands of hours.  The hours of use can be 
limited by simply turning the tube off when having only stand-by function.  
However, there is some suggestion in the literature indicating that every "turn 
on" of a tube (or an incandescent light bulb) involves rapid heating of the 
elements inside which could, immediately or over time, deform elements and 
causing sudden failure (given that the metal elements do heat unevenly--due to 
resistance in the metal--if only for a very short duration of time).  
Repetition of on-and-off cycles are thus a factor in lower tube life.

Other than these factors, it appears in the literature that operating a tube, 
particularly high power transmitting tubes, at its rated values can extend life 
IF it is otherwise not sometimes operated below or above its ratings.  It 
appears that, for example, driving an RF amplifying tube at its full rated 
power does not materially decrease its life.   Reducing drive appears not to 
extend such tubes' life.

It is all a balancing act.  73, Charly

P.S., next question is "do transistors 'wear out'?"
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