[Amps] Another interesting tube

[Carl]

Glass instead of ceramic and only a 150C seal limit means lots of air when 
trying for 1500W.
That really is an ancient technology tube and is only good to 6M.

Carl
KM1H





----- Original Message ----- 
From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
To: "AMPS" <amps at contesting.com>
Sent: Monday, July 30, 2012 1:18 PM
Subject: [Amps] Another interesting tube


> An interesting tube you might want to play with is the GU43b. About half 
> the
> price of a GS35b ($65 USD) and 1000 watts plate dissipation. It's a 
> tetrode so I
> used the swamped grid configuration. UR4LL seems to have the best price. 
> Sockets
> are expensive, but since it uses concentric ring terminals, a clever 
> machinist
> could avoid a socket entirely by using homemade spring clamps.
>
> Pix at
>
> http://www.zeitmann-tubes.com/MilitarySurplus/NosRussianMilitaryTubes/GU43B.htm
>
> which is a beautiful picture by the way. I downloaded the picture and used 
> it
> for a desktop background. Gorgeous.   :-)
>
> Some schematics at
>
> http://pa0fri.home.xs4all.nl/Lineairs/Frinear1500/FRI1500eng.htm
>
> I built an amp with one of these and it worked but with a couple of 
> caveats:
>
> 1. Although they are rated to 3.3 kVDC anode, they tend to arc with that 
> much
> voltage. Several European hams have confirmed the same thing. Hold the DC 
> down
> below 2.5 kVDC or less. The only PS I had was 3 kVDC so I gave it up.
>
> 2. There are two different base styles, differing in the center pin. Be 
> sure to
> get a matching socket when you buy the tube. I got a mismatched socket and 
> was
> able to fabricate a new center pin but it was a hassle. Get the right one 
> to
> begin with, or make your own connectors.
>
> You should be able to push a single tube to 1500 watts out but that leaves
> basically no headroom.  If I were to do it again I would use two in 
> parallel and
> hold the HV down to 2.0 kVDC or so. Lots of headroom.
>
> I'd be interested to hear from anyone who has built an amp with one or two 
> of
> these.
>
> 73, Bill W6WRT
>
>
>
>
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