>
>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,
? Let's say that a 25-ohm load were used. The swr would be 2 to 1, the
anode V swing would decrease to about half. Does this scenario seem
likely to produce a sharp rise in grid current?.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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