My 4-1000A amp will get 1800W key down output with 4400V full load
on the plate and 100W drive. At 5000V things start to arc all over
the place. It is very happy with 70W drive for 1500W output and 4400V
full load plate voltage. Tube is "new old stock", not a BC pull.
Mike, W1NR
P.S. My variac is one of the BIG 240V 28A jobs.
-----Original Message-----
From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
Behalf Of Tom Rauch
Sent: Tuesday, April 03, 2001 2:25 PM
To: Wynand van Wyk; Sam Belew; William Fuqua
Cc: amps@contesting.com
Subject: Re: [AMPS] 4-1000A Project
Hi Bill,
> Bill Orr stated in his article on Tetrodes used in grounded grid
> amplifiers (about 170 watts) but at 5 or more KV it is less than 70
I agree with that.....
> watts for full output and about 50 for full gallon (1500 watts). Also
......but that seems overly optimistic. I could NOT get 1500 watts
out with any cathode driven 4-1000A with 100 watts of drive unless
HV was nearly 6000 volts.
A 3CX1200 has a lower driving impedance, and more gain, and
barely makes 1500 watts at 3300 volts with 1000 watts of drive.
> a 1KVA variac is small not only due to the fact that the plate input
> power for 1500watts output CW would be over 2KW but that the current
> drawn by the power supply is many times the RMS value for a Capacitive
> input filter. Not so much a problem with a inductive input filter.
Yep, I'd use that 1kva variac for a filament supply. It's too small for
an anode supply even in a 500 watt output PA.
73, Tom W8JI
W8JI@contesting.com
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