[Drake] Re: Drake digest, Vol 4 #127 - 11 msgs

[Barry L. Ornitz]

Dan Martin, WB4GRA, asked:

> Anyone using modern carbon >film< resistors instead of 
> carbon composition resistors to replace the 15 ohm cathode 
> resistors in the T-4XC PA? While I'd never use metal film 
> there (save those for PS use) I'm guessing the inductance of 
> carbon film is low enough to be OK? I know you can still get
> carbon composition from some sources, Mouser included, but 
> I've already got plenty of carbon film on hand.

The inductance of film resistors (either carbon or metal) will 
be negligible in this application.  However, for stability 
purposes, I would still suggest the use of metal film 
resistors over the carbon film.  My T-4x manual lists these 
resistors as 15 ohm, 1 watt units. I have not seen many 
manufacturers of carbon film resistors that can reach this 
power level.  But small metal film resistors are readily 
available in 1, 2, 3, and 5 watt sizes at minimal cost.  I 
would suggest using the 2 or 3 watt size here.  This will 
provide plenty of reserve dissipation and only cost a few 
pennies more.

        73,  Dr. Barry L. Ornitz     WA4VZQ     ornitz@tricon.net