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[AMPS] Key down time

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Subject: [AMPS] Key down time
From: (Rich Measures)
Date: Mon, 9 Mar 98 16:47:31 -0800
>In regards to key down time on amplifiers:
>I believe any amplifier can run keyed down indefinitely given:
>1.) Proper cooling of the tube to keep it within temp limits
>2.) Heavy duty enough power supply (the tube isn't the only thing getting 
3)  If an oxide-cathode tube is used, the key-down cathode current rating is 
not exceeded.  For example, a 3cx800a7 can handle 800mA intermittently in SSB, 
but it is rated at 600mA in N-Ø-N/key-down service.  
4.  Provided that one does not do it into an antenna.
>If these two things are done, then there is really no reason why the amp 
>can't be run continuously.  
>If you doubt me, realize that a lot of 
>broadcast stations use tube amps even today.  These ARE keyed 
>continously.  They also have massive cooling and power supplies.
>While my tube amplifier experience is limited (eg: my 4-1000A), I have 
>many years of solid state amp design experience.  There is nothing  in 
>the RF design of an amplifier that would preclude it from running 
>Just my thoughts.


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

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