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Re: [Amps] Amps Digest, Vol 156, Issue 9

Subject: Re: [Amps] Amps Digest, Vol 156, Issue 9
From: Steve Wright <>
Date: Sat, 19 Dec 2015 08:17:17 +1300
List-post: <">>
who cares?  Buy another one!

On 19/12/15 06:00, wrote:
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Today's Topics:

    1. More on "baby ur radio" (Charles H)


Message: 1
Date: Fri, 18 Dec 2015 00:59:04 +0000
From: Charles H <>
To: Contest Internet <>,
        "" <>, ""
Subject: [Amps] More on "baby ur radio"
Message-ID: <BLU182-W53700D59D2F5D9EA58F864F7E10@phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

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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