[Amps] An Extra Thank You!

[Joe Subich, W4TV]

> I'm not sure I completely understand why the drive is added 
> back.  You could write a thick, thick book with what I don't 
> know about tubes, because when I went to school they weren't 
> taught anymore.

In grounded grid the drive is in series with the output.  Thus 
the drive power (less power lost in grid current and heat in 
the input circuit) adds to the output.  Adding the drive power 
to the plate input will result in a slightly low calculation 
for efficiency but will be more accurate (particularly at HF 
where drive may be closer to 100 Watts) than ignoring it. 

73, 

   ... Joe, W4TV 
  



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Jeff Carter
> Sent: Thursday, March 05, 2009 4:23 PM
> To: amps at contesting.com
> Subject: Re: [Amps] An Extra Thank You!
> 
> 
> I didn't add the drive back in on mine, so I'm off by that 20W.
> 
> I'm not sure I completely understand why the drive is added 
> back.  You could write a thick, thick book with what I don't 
> know about tubes, because when I went to school they weren't 
> taught anymore.
> 
> Jeff/KD4RBG
> 
> ---- Original message ----
> >Date: Thu, 5 Mar 2009 16:11:14 -0500
> >From: "Joe Subich, W4TV" <lists at subich.com>
> >Subject: Re: [Amps] An Extra Thank You!
> >To: "'KB0NLY'" <kb0nly at mchsi.com>,<amps at contesting.com>
> >
> >Efficiency (assuming grounded grid) = Pout/(Ip*Vp+drive)
> >
> >You don't give the plate voltage so I'll use 2000V as a 
> placeholder ...
> >
> >Efficiency = 450 / ((.375 * 2000) + 20)
> >           = 450 / (750 + 20)
> >           = 450 / (770)
> >           = 58.4%
> >
> >73,
> >
> >   ... Joe, W4TV
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