----- Original Message -----
From: "Jim Thomson" <jim.thom@telus.net>
To: "Carl" <km1h@jeremy.qozzy.com>; <amps@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 4CX1000A/1500B and the FU's are all high gain tetrodes that take very
little drive in AB1 swamped grid driiven. When almost no POWER was required
they, the 8122, and other similar tetrodes were about equal in that
respect..
My NCL-2006 conversion uses a tuned circuit for impedance step up to the
grid and a 50 Ohm resistor at the input and easily does 1300W with 12W drive
from the transverter.
The 4CX's were used in a few commercial/military TX and plain grid driven
using receiver type tubes. Others used a loafing 4CX300A or 8122 in either
cathode drive or swamped grid where quick QSY was needed.
Carl.
---
This email has been checked for viruses by AVG.
https://www.avg.com
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|