[Amps] Filament Voltage Question
Fuqua, Bill L
wlfuqu00 at uky.edu
Tue Apr 22 13:37:04 EDT 2014
Thinner and longer filaments also have more inductance.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces at contesting.com] on behalf of Radio WC6W via Amps [amps at contesting.com]
Sent: Tuesday, April 22, 2014 11:28 AM
To: Jim Garland; amps at contesting.com
Subject: Re: [Amps] Filament Voltage Question
Hi Jim,
That tube employs a DIRECTLY heated filament.
Two good reasons for low voltage in this case:
High voltage operation would require thin elements that would be mechanically fragile.
Current distribution would be way whack with the potential differences in a high voltage setup and induce lots of hum.
73 & Good morning,
Marv WC6W
http://qsl.net/wc6w/
--------------------------------------------
On Tue, 4/22/14, Jim Garland <4cx250b at miamioh.edu> wrote:
Subject: [Amps] Filament Voltage Question
To: amps at contesting.com
Date: Tuesday, April 22, 2014, 8:19 AM
I was reading the data sheet this
morning on the 4CX3500A and noticed the
filament requirements are 5V at 90Amps. It occurred to me
that I've never
understood why so many tubes with indirectly heated cathodes
have such
low-voltage - high current filaments. Since the only thing
the filament is
used for is to heat the cathode, then why not design it to
run at, e.g.,
115V at 4A? That sure would be a lot easier to implement. I'm
sure there's a
reason, howevrr, and would appreciate somebody informing of
it!
73,
Jim W8ZR
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