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Re: Tube Coils (fwd)
---------- Forwarded message ----------
Date: Mon, 24 Feb 1997 11:22:22 -0500
From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
To: Tesla List <mod1-at-pupman-dot-com>
Subject: Re: Tube Coils (fwd)
> Date: Sun, 23 Feb 1997 21:06:18 -0700 (MST)
> From: Tesla List <mod1-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Tube Coils (fwd)
>
>
> ---------- Forwarded message ----------
> Date: Sun, 23 Feb 1997 16:45:50 -0500 (EST)
> From: VonPostel-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Tube Coils
>
> Noticed a request for information on figuring perimeters for vacuum tubes.
> These all give the method for calculating tube operation when you have the
> characteristic curves.
>
> Application Bulletin Number 4
> "Class C Amplifier Calculations"
> Eitel-McCullough, Inc. Copyright 1948
>
> I haven't asked EiMac for help in a lot of years, but they used to be very
> generous with their assistance. At one time they made a line of triodes
> having a large reserve of cathode power. That makes them particularly
> adaptable to pulse type applications. Typical of these are the 250-TH,
> 250-TL, 304-TH, 304-TL, 450-TH, and the 450-TL. The number of the tube is the
> plate dissipation in watts. TH means a "high mu" tube and TL means a "low mu"
> tube. All of the foregoing were designed to run "Cheery Red" at maximum
> plate dissipation. All are radiation cooled. (Fans not needed if there is
> free circulation of air.). They can all be operated up to about 30 MHz with
> out de-rateing because of frequency limitations.
> Type: Filament Voltage: Filament Current
> 250T- 5.0-5.1 10.5 A.
> 304T- 5.0 25 A
> or 10 12.5 A.
> 450T- 7.5 12 A
>
> As a suggestion, if you are think about building a coil which will be pulsed,
> take a close look at the 304-TH or 304-TL. They were originally designed for
> such service in radars and were pulsed into the megawatt power region.
>
> As an aside, sockets for all of the above, as well as the 833-A were at one
> time made by the E.F.. Johnson Co. I don't even know if they are still in
> business nor if they are, they still make that type of thing.
>
> The same thing is published (almost exactly) in:
>
> "The Radio Handbook", 11th, 13th, and 14th editions, Copyright 1947, 1951,
> 1956
> Editors and Engineers Ltd.
> Summerford, Cal.
>
> You may find that one of your older ham friends will have a copy of the
> handbook. The most information on r.f. amplifiers is contained in the 14th
> edition. So if you ask your public library for an inter library loan, try
> and get the 14th edition.
>
> Hope this is of help.
>
>
VonPostel, All,
I just scored some 1949 vintage RCA HF military groundstation
transmitting equipment. Each of the four transmitters had a pair of
gorgeous 450TH Eimac triodes. I thusly have the sockets and
filament transformers as well. Two of these tubes had broken
filament strands from shipping abuse and are now being displayed
proudly in my dining room china cabinet. They are very pretty being
about a foot tall with a 5 inch diameter globe containing the working
ingredients.
By looking at the remains of the filament in one of these damaged
tubes I don't see any white oxide color on these thin tungsten
needles. Can anyone out there establish for certain whether these
are straight, unthoriated tungsten filaments? I guess I could tell
from the filament color but I haven't plugged one of these jewels in
yet. This tube looks about the electrical equivalent of an 833-A.
For performance/cost and modern times availability I'd build 833-A's into a
vac-tube TC, but for a piece of tabletop art, I'd certainly want these in it.
I've NEVER run across any of these tubes surplus, so I suspect they
are rather rare nowadays.
rwstephens