[TenTec] Ten Tec amps and ALC

[Jim Brown]

On Wed, 18 Aug 2004 12:06:58 -1000, Ken Brown wrote:

>y Titan 425 has an OVERDRIVE indicator. If I ever operated SSB, AM, 
>PSK31 or other modes where multiple tones are used and amplitude 
>linearity is important, I would adjust my exciter power level to make 
>sure that the OVERDRIVE indicator on the Titan never comes on.

The overdrive indicator is important for something even more important 
than linearity -- the life of the output tubes!  

3CX800A7's do not like to be overdriven, and the manual has a bold 
print warning that 120 mA of grid current should NEVER be exceeded. 
This element of the tube's rating is, apparently, even more critical than 
plate current or dissipation. 

I have learned that Eimac has a newer version of this tube designed for 
pulse operation and with an internal  structure higher voltage rating 
(3500V). It is directly interchangeable with the 3CX800A7. As near as I 
can tell, there are no changes in the grid current rating.

A power amp using the 3CPX800A7 at a higher plate voltage could be 
driven far more easily than one using the 3CX800A7, making it far less 
likely that it would be overdriven. 

Here are some interesting links on the topic. 

http://www.hamradiomarket.com/articles/Titan%20P%20Hybrid.htm

http://www.cpii.com/eimac/ab25.htm

Jim Brown  K9YC