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[AMPS] Re: Drive Level in amplifiers

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Subject: [AMPS] Re: Drive Level in amplifiers
From: (Phil Clements)
Date: Tue, 24 Mar 1998 01:03:59 -0600
At 10:51 PM 3/23/98 -0600, you wrote:


>>During ssb modulation, the drive varies widely during each spoken word.  
>>However, max. peak drive and max. anode-I is essential to correct tank 

Normal voice waveforms have in the vicinity of a 3.5:1 peak to average ratio.
This must be taken into account when computing the input impedance to a
grounded grid amp.
>What does correct tank adjustment have to do with the input impedance?

Because as the cathode current is changed, the input impedance also

The input impedance is the ratio of input drive power to peak cathode

>However, what does the flow of grid current have to do with tube 
>impedance?  Maybe I am showing some ignorance here, but again, I haven't 
>seen this.

The flow of grid current is the RESULT of the flow of cathode current.

  Zin = Pin/I2 (input impedance equals power input divided by peak cathode
  current. Peak cathode current is 3.5 times(+/-) average.
When you come up with a value from the above formula, you can then substitute
a non-inductive resistor of the calculated value for the tube and use your
noise bridge or MFJ analyser to park your tuned input in the middle of the


Phil, K5PC

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