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Re: [Amps] Super Cathode Driven Tetrodes

To: "Carl" <km1h@jeremy.qozzy.com>, <amps@contesting.com>
Subject: Re: [Amps] Super Cathode Driven Tetrodes
From: "Jim Thomson" <jim.thom@telus.net>
Date: Sat, 27 Oct 2018 12:51:23 -0700
List-post: <mailto:amps@contesting.com>
<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
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