[Elecraft] Amplifier Input Impedance

[WILLIS COOKE]

I would say no to all three questions.  The input impedance to the amp will not be the same when it is not powered and driven.  The SWR indication on the driver will give you some idea of the input impedance.  It should not hurt the antenna analyzer if the amplifier is not powered, but I don't think it will tell you anything useful.  With power on the amp, it might.

Willis 'Cookie' Cooke 
K5EWJ


--- On Mon, 1/26/09, Stephen W. Kercel <kercel1 at suscom-maine.net> wrote:

> From: Stephen W. Kercel <kercel1 at suscom-maine.net>
> Subject: [Elecraft]  Amplifier Input Impedance
> To: 
> Cc: elecraft at mailman.qth.net
> Date: Monday, January 26, 2009, 9:17 PM
> Fellow Elecrafters:
> 
> Is it possible to measure the input impedance of a linear
> amplifier by 
> using an antenna analyzer (such as the Pal Star) at the
> input of the 
> amplifier in place of the rig?
> 
> Would the amplifier input impedance be the same for the
> very small 
> signal that the analyzer generates as it would be for the
> 80-100 Watt 
> drive from the rig?
> 
> Is there any risk of damaging the analyzer (i.e., should I
> put a 
> blocking capacitor between the analyzer and the rig?) by
> attempting the 
> measurement?
> 
> Thanks,
> 
> Steve Kercel
> AA4AK
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