[Amps] Super Cathode Driven Tetrodes

[Carl]

----- Original Message ----- 
From: "Jim Thomson" <jim.thom at telus.net>
To: "Carl" <km1h at jeremy.qozzy.com>; <amps at contesting.com>
Sent: Saturday, October 27, 2018 3:51 PM
Subject: Re: [Amps] Super Cathode Driven Tetrodes


> <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

The 8410 is power limited to keep the FCC happy.
I guess they got a bit peeved when so many 8K's went to hams!



> 


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