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[AMPS] Re: 4-1000A Impedance Variations

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Subject: [AMPS] Re: 4-1000A Impedance Variations
From: (Rich Measures)
Date: Mon, 23 Mar 98 15:47:20 -0800
>> The input Z of a tube in g-g config. varies greatly, depending on drive 
>>level.  When drive level is low, input Z is high.  When the drive is 
>>high,  the input Z is low.  Thus, a noise bridge, which uses uses a 
>>miniscule level of RF, provides no clue.
>Everybody claims this, but I haven't seen it.  The input impedance does 
>NOT vary with input power.  I have the exact same match applying 100 
>watts as I do 5.  My SWR does not change.  

You are talking about measuring swr with a tuned circuit/flywheel at the 
cathode.  Cathode impedance, this is not.  You must measure direct into 
the cathode? .  .  One problem with a noise bridge is that the power is 
in the microwatt range.  .  
>Also, with a solid state rig, how can I apply full drive with a bad 
Make C1 equal to 25 ohms of Xc (450pF @ 14MHz).  Vary L1 and C2 until you 
obtain a 1.2 or better swr.  The radio should then be able to deliver 
full output.   


R. L. Measures, 805-386-3734, AG6K   

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