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[AMPS] L-Net calculations: Am I doing something wrong?

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Subject: [AMPS] L-Net calculations: Am I doing something wrong?
From: (Jon Ogden)
Date: Tue, 16 Feb 99 15:47:48 -0600
>>Depending on his output impedance, he may have a very difficult time 
>>matching with that much capacitance and still get a Q that is overly 
>>large.  With the 4-1000A, there is no way to match its high impedance down 
>>to 50 Ohms and still get a good Q w/o doing this transformation.
>?  Wanna bet a large pizza with 4-toppings?

Sure, I've been asking this question for the last week and you've never entered 
the fray.

The 4-1000A has an output impedance of 4600 Ohms (according to Eimac) at 5KV 
anode voltage.

The B&W 850A has an inductance of about 0.8 nH on 10M.  The required tune C at 
that point is on the order of approx 23 pF (if memory serves me).  However, the 
Q is above 40.  To lower the Q, one would need to increase the inductance a 
bit.  However, the UCS-300 (which I use) has a minimum capacitance of 10 pF.  
The Cout of the 4-1000A is 7.6 pF.  That makes a minimum parallel capacitance 
of 17.6 pF.  If L is increased enough to lower the Q to a reasonable level, the 
required Ctune will be lower than 17.6 pF which is not realizable.

So, if you can explain how to do it, I'll buy you whatever pizza you want.



ps: Exact values of the network are on my computer at home. I can reproduce 

Jon Ogden

"A life lived in fear is a life half lived."

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