[Amps] Super Cathode Driven Tetrodes

[Jim Thomson]

<That seems very low drive for passive grid. The NCL-2000 could use up to
<100W in the high drive positon at 50 Ohms and 20-25W into the low drive 100
<Ohm configuration.

<Carl

##  NCL-2000  didnt use a 4CX-1500.   He used bird wattmeters on both sides 
of the hb  4CX-1500B.   10 watts for 1.5 kw on low bands
and  20 watts on upper HF bands.  Dunno how much  B+  and screen voltage 
used.    I believe he terminated the grid with a 50 ohm globar  he
removed from his heathkit dummy load.

## Local buddy has an Alpha  8410, with a pair of
4CX-1500Bs.  Dunno how much drive it requires, I will  ask him.
He sez it does an easy 2 kw output on 80m.

##  Those  OM-4000  amps, that use  a pair of chinese FU  tetrodes,  sorta 
their version of a
4CX-1500B,  only require 20-25 watts of drive for  4+  kw output...per the 
folks I know that own them.
A fellow in Colorado I know, just bought the manual tune version of the 
OM-4000.  Input attenuator removed,and an easy 5 kw out.
They removed the  FCC  approved input attenuator, or bypass the attenuator. 
Then they end up with the
same version OM-4000  as the rest of the planet gets.

##  Remember that  tetrode that Rich built ?   He used a  surplus  500 ohm 
globar and a 1:9  trifilar .  20 db gain.   Ideally,
a  450 ohm globar is used.  Then a small amount of uh in parallel with the 
globar, to cancel out the tubes stray input  C /  XC.

##  Im not a grid driven tetrode  expert, with minimal experience, except 
for the G2DAF  congig..... which I would not recommend to anyone.

Jim   VE7RF