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[AMPS] 4cx300's on 6 query

To: <amps@contesting.com>
Subject: [AMPS] 4cx300's on 6 query
From: measures@vcnet.com (measures)
Date: Wed, 6 Oct 1999 12:46:28 -0700
>
>Rich-
>
>The specs say approx 30pf input
>
>rough figuring.....
>2 tubes 60pf

The max. grid C is 16pF per 4cx300A

>misc wire and socket TT about 100pf

stray C on the grid is a few pF. 

>Xc@50Mc about 30k ohms.
>
Xc of 32 pF at 50MHz is 138 ohms. 

>The specs also say the tube wants about 2.5W
>drive. 2 x tube about 5W. 
>
For Class C, not for Class AB1.  

>If I have 10W and I want 60V and half the power
>is going into my tubes and half into my resistor it looks
>like a 1:6 turns ratio and an 1800ohm resistor will get me
>the right swing from my 10W and look  like 50ohm to the
>exciter.
>
>So, why do I need tuned input?
>
You need 60v pk to drive the grids.  10w-rms / 50-ohms is 32v pk.  A 
bifilar toroidial tranformer would increase the potential to about 60v 
peak.  The terminating R would be 200 ohms.  

-  later, Bob.  
>
>
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-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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