[AMPS] Re: New G2DAF amplifier information

[Peter Sundberg]

Gents,

These are the parameters of the QBL 5/3500 used by me and others in a G2DAF
circuit. The parameters are taken from the manufacturers book.
HF Class B amplifier, single sideband (there are numbers for class B and C
in the book)

Vf 6.3 V
If 32.5 A
Direct heated thoriated thungsten
Va 5 kV
Vg2 800 V
Vg1 -107 V
Ia 1.3 A
Ig2 75 mA
Ig1 55 mA
Wia 6.5 kW
Wo 4.4 kW
n 68%

Max ratings at 110 MHz in class B are:
Va 5 kV
Ia 1.3 A
Vg2 800 V
Wg2 100 W
Ig1 80 mA

The xerox copies I have are not good enough for scanning and publishing as
they are faded and the paper has turned yellow. Will try to copy them again
and then scan them.

The tube is mostly used in TV transmitters up to 250 MHz, class B,
television service.

Ciao,
Peter/SM2CEW

At 14:57 2000-03-17 -0800, you wrote:
>
>Rich said:
>
>"Any guesses at to what would happen if a 8660/4CX1500B were used in a DAF
>circuit. - with say 20mA of grid current instead of 0.06mA of grid current?"
>
>Rich:
>
>I have heard no one - except you - suggest using an 8660 in a DAF circuit.
>Your friend, Norm, used 4CX250 tubes in a mis-understood bastard adaptation
>of the original G2DAF circuit, which hung an electrolytic capacitor on the
>screen grid.  It splattered badly.  It was not a G2DAF circuit.  Yet, you
>use it as a basis to condemn any reasoning that is not consistent with the
>world as you view it.
>
>Tubes do not have to be used as the tube manufacturer originally intended
>them to be used, and amateurs by their very nature are experimenters.  I
>recently built an oscillator which used the screen as the plate.  It works
>fine.  Tubes were not intended to be used that way.  It is called a Dynatron
>and was designed long before I was born (which is getting rare these days).
>Building any circuit - "good" or "bad" - is fine, so long as the builder
>makes sure he does not unreasonably splatter.  Certain tube design
>parameters must be met for the long term health of the tube.  Beyond that,
>the only other question is whether the output has undesireable
>characteristics such as splatter, harmonics or parasitics.  And, it is up to
>the designer or builder to achieve those goals.  It would be a boring world
>if all the amplifiers looked exactly the same and used exactly the same
>tube.
>
>The other day, I raised the question of increasing the screen voltage on a
>grounded grid tetrode - from zero to something less than the "normal"
>voltage.  Your response was "DAF circuits produce feculance".  The
>"distortion"  was in your response.   I am sorry that Norm's splatter years
>ago affected your outlook on life so much.
>
>73,  Colin  K7FM
>
>
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