[Amps] FW: 4CX5000A in common grid circuit

[peter chadwick]

I have a feeling that to get the higher gain in gg with a tetrode will require there to be volts on the screen grid. If it's directly grounded, you need a big drive signal to get the peak plate current and that could over dissipate the grid.

73

Peter G3RZP


========================================
 Message Received: May 05 2013, 07:05 AM
 From: "Markku Oksanen" <ww1c at outlook.com>
 To: "jtml at losalamos.com" <jtml at losalamos.com>, "amps at contesting.com" <amps at contesting.com>
 Cc: 
 Subject: [Amps] FW:  4CX5000A in common grid  circuit
 
 
 
 
 
 
 All
 
 I found this 
 http://www.cpii.com/docs/related/22/C&F4Web.pdfand it looks like chapter 4 of Pappenfus' if I understand it correctly.
 Against current "wisdom" this states (page 104)  that a properly designed tetrode in GG will give a gain of 20 to 50 while triodes tend to remain below, at the level of 7 to 20, 20 seems to be a sign of a good design these days with modern high muu tubes.  
 Can anybody help with this???  Is this correct?  I have never before heard that tetrodes in GG can give such high gain. Are there specific requirements for the tube??
 I still didn't find direct gain formula but managed to calculate some estimates based on voltage gain and impedance levels.  What the GG muu value to use with a tetrode is, I don't quite know.
 Looks like it makes good sense to try a GG design first with the some forethought in case grid drive becomes a necessary change later. Gain of over 20 is plenty good enough.
 Thanks for the hint / help!
 
 
 Markku WW1C
 
 > Date: Thu, 2 May 2013 16:28:16 -0600
 > From: jtml at losalamos.com
 > To: amps at contesting.com
 > Subject: [Amps] 4CX5000A in common grid  circuit
 > 
 > 4CX5000A is in the Collins design in the 1964 Ed of Pappenfus' SSB Principles. It will give you a reference point. If you can find the NAB handbook from the 1986 era, I wrote the section in FM transmitters, comparing a 4Cx3500A in to and gg circuits, class c though, at 100 MHz. Its a similar but better tetrode. If you put voltage on the screen you can get fairly high gain, like 12 db I think. Memory may be fading here.
 > 
 > Sent from on the road...
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