Graham wrote:
...other knowledgable persons on the reflector -
> could you please
> explain how heavy plate loading and reduced efficiency can increase tube
> life.
Heavier loading as Carl describes will only very slightly reduce efficiency,
however there will be a dramatic decrease in grid current. Too much grid
current can be a faster tube killer than too much plate current especially
in "toy" tubes.
For example: a 3CX800A7 can dissipate 800 watts in the plate but only only a
tiny fraction of that in its grid, 4 watts. This is why you find the grids
of such tubes protected up the ying-yang. Poor loads (higher than 1.5:1 SWR)
are difficult for this class of tube to tolerate as grid current rises
sharply.
73, Dan Magro W7RF, (President WARC 1999, member SCDXC, SCCC)
Manufacturers Rep & Distributor for HENRY RF Power Amplifiers.
www.radiodan.com <http://www.radiodan.com> ??? RFpower@radiodan.com
<mailto:RFpower@radiodan.com> A trip to our web site is worth the click!
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