Re: Tube coils for beginers 2

To: tesla-at-pupman-dot-com
Subject: Re: Tube coils for beginers 2
From: David Trimmell <dwt-at-efn-dot-org>
Date: Sun, 26 Jan 1997 18:00:07 -0800
Subscriber: dwt-at-efn-dot-org Sun Jan 26 22:17:53 1997

Mark,

> 
>    David a 4cx250 will work, but DON'T take the usual route with this
> tube and tie the screen and control grids
> together to simulate a triode, if you try to run it this
> way you stand a VERY GOOD chance on distroying the tube.
> 
>  This tube must be run as a tetrode with voltage on the
> screen, you could run the screen and control grids tied
> together via a capacitor for a common RF connection but
> not common for AC/DC potential because the screen under
> these conditions will draw excessive current as its
> Mu factor is much higher than the control grid.
> 
>  The 813, 803, 4-1000, 4-125 thru 4-500 tubes can be run
> in the triode connection safely.
> 
>  Good triode tubes are: 811A, 572B, 3-400, 3-500, 3-1000,
> 833 etc.
> 
>                         Mark Graalman (WB8JKR) TCBA#1399

When you say "you could run the screen and control grids tied together
via a capacitor for a common RF connection" what would be a proper way
to calculate that value of capacitance? I may start out using these
4cx250's as they will be free, but still have little desire of killing
them to soon! 

Thanks,

David Trimmell <dwt-at-efn-dot-org>