[BC] getting the right tube combinations

[Jerry Mathis]

On 8/5/06, Jim Tonne <<mailto:tonne at comcast.net>tonne at comcast.net> wrote:


I think the use of the 4-400 etc was based on the thought that
a simple driver could be used;  as I recall it was just an 807.
The 833s, while remarkably robust and tolerant of improper
loads etc did require a hefty driver.

....Which Harris DIDN'T do either. BC-1G and similar 1 KW, RF drivers 
are a pair of 807's. It worked, as long as the 807's were in top 
shape. As soon as they started to weaken, you started loosing 
positive modulation, until finally you couldn't even make full 
carrier power. Of course, they seldon got that weak; the horizontal 
mounting of the 807's caused the grids to sag, and they usually 
shorted out and blew the PS fuse long before then.

I know I've said this before, but the best 1KW AM transmitter I ever 
saw was the Raytheon RA-1000. 833's driven by a PAIR of 813's on the 
RF side, and by 845's on the audio side. You could run the 833's 
forever in that transmitter, it seemed.

-- 
JM