Exactly, John. If a transmitting tube is operating within manufacturer's
specifications and does not show color then don't increase the plate current
or voltage to do so.
Many transmitting tubes are meant to show some blushing, particularly,
modulators - this is normal and acceptable.
You wouldn't, of course want to this occur with a 6146, etc.
My point was that many hams mistakenly think that with some tubes like those
that I mention there should be no blushing - quite the contrary. Blushing
is good for tubes and, of course, for women, under certain circumstances!
Merry Christmas
Dave, W3ST
Publisher of the Collins Journal
Secretary to the Collins Radio Association
www.collinsra.com - the CRA Website
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----- Original Message -----
From: "John Lawson" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio in the Amateur Service"
<[email protected]>
Sent: Monday, December 11, 2006 12:50 PM
Subject: Re: [AMRadio] Screen Modulated 813
On Mon, 11 Dec 2006, david knepper wrote:
Zirconium getters best at about 1000 degrees C, this why large metal
anode transmitting tubes like the 4-400A, 4-1000A, and 3-500 must be
operated with a dull red to red anode color. Zirconium also releases
some gasses and
[snip]
You can do what you will but I like to run a little color on my large
bottles.
You're making the same point I am, Dave: "visible plate incandescance"
can be 'optimum' - 'acceptable' - 'acceptable for x-time' - 'not
recommended - or 'disastrous'. It's device-dependent!
All of it is a matter of physics, physical electronics, metallurgy, and
the well-known, well-documented aspects of thermionic device design and
contruction. It is not so much a matter of desire or personal inclination,
as it is: at the operating point you have set for the particular device in
use - is it within the manufacturer's ratings for that service? If the
plate shows visible color, so be it. If, on the other hand, a noticeable
blush means the tube is exceeding it's design-spec, then some consequences
will come from that... "good" or "bad" I cannot say. If an expensive
power tube has it's useful life cut in half, or more, from 'abuse' -
especially if it's a fairly 'rare' type - well then....
Dat wuz all I wuz tryin' t' say.
Cheers and Best of the Season!
John
KB6SCO
DM09fg
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