[Elecraft] Tube Linear Amp design for basic K2

[William Tipton]

   Eimac  introduced the 8166/4-1000A in 1945 as part of its postwar line
   of  glass-envelope, radial  beam   tetrodes  which  also  included the
   4-65A,  4-125A, and 4-250A; and later in 1947, the 4-400A, essentially
   a 4-240A upgraded with a finned anode (plate) radiator.

   External  anode,  forced-air  cooled  tetrodes and pentodes were later
   developments.  Penta  Labs  developed the 8295/PL-172 pentode--a later
   version,  the  8295A  had ceramic instead of glass insulators, but the
   same   1000W  plate  dissipation  rating.  Penta,  Eimac,  and  others
   manufactured this tube. Comparable EIMAC external anode tubes were the
   8168/4CX-1000A  radial  beam tetrode and the 4CX-1500B, both specially
   designed for AB1 linear amplifier service.

   The  Russian  4CX-800  and 4CX-1600 tetrodes marked under Svetlana and
   other  brand  names  are  as  far  as  I know the most recent designs,
   incorporated striped cathode structure to reduce grid interception and
   differential cathode-to-anode radius to reduce secondary emission.



   William L. Tipton, Jr.

   1332 Pinewood Road

   Jacksonville Beach, FL 32250-2941

   904-241-0134


       ______________________________________________________________

     From: "Wyn" <vr2ax at attglobal.net>
     To: <elecraft at mailman.qth.net>, "Charles Greene" <crgreene at cox.net>
     Subject: Re: [Elecraft] Tube Linear Amp design for basic K2
     Date: Sun, 11 Jun 2006 15:51:52 +0800
     >Chas,
     >
     >Thanks  for  your  comments.  It's interesting to see that someone
     else
     >has come to some very similar fairly similar basic conclusions as
     >oneself.
     >
     >I have emailed RF Parts for the current price of the 4-1000a. At
     >this stage, it may remain a drwing board exercise..
     >
     >73s,
     >Wyn
     >
     >
     >----- Original Message ----- From: "Charles Greene"
     ><crgreene at cox.net>
     >To: "Wyn" <vr2ax at attglobal.net>; <elecraft at mailman.qth.net>
     >Sent: Saturday, June 10, 2006 3:46 AM
     >Subject: Re: [Elecraft] Tube Linear Amp design for basic K2
     >
     >
     >>Wyn,
     >>
     >.... A 4-1000A is the nearest new(er) design tube. I
     >>thought about how I could make the old guy put out something
     >>exciting when driven by my K2. I could swamp the input with a 200
     >>ohm  resistor  and  use  a  4:1 balun and the impedance to the K2
     would
     >>still be 50 ohms. ...... The tube itself does not take any power
     >>in  class  AB1,  but  the input voltage needs to be so much for a
     given
     >>output. A 4:1 balun would increase the drive voltage by a factor
     >>of  4  times  which  would increase the output of the amp to 1600
     watts
     >>if  the  drive  remained  the  same,  800  watts  with  10  watts
     drive......
     >> From 20 watts to 1600 watts is a power gain of 19 dB which in my
     >>opinion  is  a  little  high.  I would be more comfortable with a
     power
     >>gain of 16 dB, but you can try it.
     >>
     >>....... Those tubes are expensive.
     >>
     >>73, Chas W1CG
     >
     >_______________________________________________
     >Elecraft mailing list
     >Post to: Elecraft at mailman.qth.net
     >You must be a subscriber to post to the list.
     >Subscriber Info (Addr. Change, sub, unsub etc.):
     >http://mailman.qth.net/mailman/listinfo/elecraft
     >
     >Help: http://mailman.qth.net/subscribers.htm
     >Elecraft web page: http://www.elecraft.com