[AMPS] CENTURION HELP

[w8jitom@postoffice.worldnet.att.net]

> Shortly after the first article on parasitic suppression was published in 
> the October 1988 issue of  *QST*, Ten Tec reportedly tried using low 
> VHF-Q/low VHF-Rp parasitic suppressors.  However, during 28MHz operation, 
> the Ten Tec engineers observed signs of heating in the VHF suppressors, 
> so they went back to using their conventional suppressor design, which 
> ran cooler at 28MHz

Actually two manufacturers tried and abandoned the nichrome. Neither 
manufacturer noted any improvement in field service. The Ten Tec tube 
problems were related to the lack of grid protection, and operators 
bumping the grid's too hard.

It's my understanding Ten Tec's later amps included an electronic 
overload to protect the grids, and that improved tube life by 
preventing destructive operator error.

The grid dissipation limit of a 3CX800 is reached at about 130 mA per 
pair of tubes. Gold migration increases rapidly as you approach that 
limit, and eventually can cause a tube arc. 

73, Tom W8JI

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