[AMPS] Re: What is G2DAF..?

[Lars Harlin]

-----Original message-----
From: wb8jkr@juno.com <wb8jkr@juno.com>
To: AMPS@contesting.com <AMPS@contesting.com>
Date: 30 oktober 1998 13:20


>
>  Anyone,
>
>
>  Ok, Ok, I can't stand it. It may be a dumb
>question but just what is the 'G2DAF' design,
>and the principles behind it?
>
>Mark  WB8JKR


Ok, Here are the basic principles of G2DAF design:

1.) It uses one or more tetrodes.
2.) It has a conventional outputside; pi- or pi-L-filter.
3.) The unique thing is the inputside, wich is a methode to obtain both screen voltage and griddrive from
      the very same source; Your exciters RF-output!
4.) The class of operation is FLOATING and not FIXED as with most other amps. Facts wich applies to
      tetrodes with FIXED class of operation, for example Eimacs statements on screenregulation versus
      linearity, does NOT apply to this amp and this class of operation.

To achieve the above, the technique is to feed a small part of the the drivepower to the grid of the tube and
the mainpart thru an RF rectifier, voltagemultiply it and feed it to the screen. Some measures must be taken
in order to get an appropriate balance between grid- and screendrive.

Then, why use this circuit?

1.) Simple design. No screen- or biassupply is required.
2.) High gain. Up to 20dB. Low drive requirements.
3.) Efficiency. Higher pulse power than with other circuits. Tube is almost cut off with no drive.
4.) Finally, and appearantly most controversial, very good linearity - proven by means of on air tests
     as well as plots from HP spectrumanalyzer, using speech (NOT 2-tone Rich..!)

"Life is to short for QRP"!

73 de Lars/SM3BDZ


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