[Amps] Schematics  for 4CX250B GG HF amplifi er

[Bill Fuqua]

  That is real interesting since it is so rarely used here in the USA.
Can you find an example. It makes since, the simpler the better as far as
I am concerned. I have also thought of using some of my external tetrodes and
pentodes in the same mode. I have 4cx1500, 5cx1500 and 4cx5000 tubes around.
the 5k may be a bit too much.
   One neat thing about the 4cx series is that the screen grids are in the 
shadow of the
control grid so there is very little screen current under normal 
circumstances.
Grid current, I believe, contributes to the nonlinearity of the amplifier. The
distortion advantage of the negative feedback due to the cathode to ground 
impedance is
diminished when the plate current is not equal or at least proportional to the
cathode current.

73
Bill wa4lav



At 03:01 AM 8/16/2012 +0200, Peter Voelpel wrote:
>Amps like that have been common for Swiss (Zellweger) and DDR (RFT)
>military.
>
>73
>Peter, DJ7WW
>
>-----Original Message-----
>From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
>Behalf Of Bill Fuqua
>Sent: Donnerstag, 16. August 2012 02:23
>To: g8on at fsmail.net; JeanPierre.Behiels at electrabel.com; amps at contesting.com
>Subject: Re: [Amps] Schematics  for 4CX250B GG HF amplifier
>
>Every once in a while we revisit this topic.
>I will just cut and paste the following from some time ago.
>
>Bill Orr's article about super cathode driven tube amps in the July 67 QST.
>He has a example of a 4CX300A (control grid connected to cathode) cathode
>driven amplifier.
>It only has a power gain of 5.     375 watts out with 75 watts input. But
>the
>nice thing is that the 3rd order products were 46db down and 5th were -49.
>This is quite an improvement over most amplifiers.
>      I have always wanted to do this using two stages one produce around
>300watts output and the second 1500 watts.
>A 4CX250b driving 4 parallel 4CX250B tubes. Should get similar results.
>This naturally would require 50 to 70 watts drive.
>
>73
>Bill wa4lav
>
>
>At 06:31 PM 8/15/2012 +0200, peter chadwick wrote:
> >The 4CX250B is not suitable for use in the classic GG arrangement. Go
> >to http://ahars.com.au/documents/eimac01.pdf  for an explanation.
> >73
> >Peter G3RZP
> >
>
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