Re: [Amps] mega mobile

["on4kj" <on4kj@skynet.be>]

  Good point Rich.
  Guess most of us nearly forgot. Others never knew........

  Jos on4kj


  ----- Original Message ----- 
  From: "R.Measures" <r@somis.org>
  To: <peter.chadwick@Zarlink.Com>
  Cc: <amps-bounces@contesting.com>; <ka1xo@juno.com>; <amps@contesting.com>
  Sent: Monday, May 03, 2004 4:08 PM
  Subject: Re: [Amps] mega mobile


  >
  > On May 3, 2004, at 2:09 AM, peter.chadwick@Zarlink.Com wrote:
  >
  > >
  > >
  > >
  > >
  > > Rich said:
  > >
  > >>   Triodes have Mu, tetrodes have Gm.
  > >
  > > Any tube with more than 1 grid has a mu.
  >
  >   Good point, Peter.  However, triodes are rated in Mu and tetrodes
  > are rated in Gm.
  >
  > > How relevant it maybe is another
  > > matter.
  > >
  > > mu is dVa/dVg, and is also  gm times ra (mutual conductance times
  > > anode/plate resistance)
  > >
  > > In a pentode or beam tetrode, where normal operation produces a
virtual
  > > cathode between screen and plate, plate voltage has relatively little
  > > effect on plate current, and thus ra is very high and so is mu.
Several
  > > transmitting tubes have a relatively low ra - the 6146 comes to mind -
  > > so
  > > varying plate volts does affect plate current to a much greater extent
  > > than
  > > in a small signal pentode such as a 6BA6. But gain is still
  > >
  > > (mu times Ra)/ (Ra + Rl)
  > >
  > > Rl is the plate load impedance.
  >
  >   yea, verily
  >
  > Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
  >
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  >
  >


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