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Re: [Amps] Transceiver Output Impedance

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Subject: Re: [Amps] Transceiver Output Impedance
From: "David Cutter" <>
Date: Sun, 9 Mar 2008 12:18:25 -0000
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One of these days I will try the following experiment.

I will MAKE a rf signal generator and add resistance in series with it to a 
load of 50ohms and stop adding resistance when the load voltage is half the 
open circuit voltage.  I will then assume this signal generator has an 
output impedance of 50ohms.  OR I will take a "known" 50ohm signal generator 
and test it for open and loaded output voltage.

Then I will take say an ICE bandpass filter that has been tested on someone 
else's high grade test rig and characterise it on my signal generator with a 
50ohm load.

Then I will do the same with a transmitter and see if the results are the 
same.  If they are, I will assume that my transmitter is also 50ohm "output 

Then I will be more sure which side of the fence to drop.

I suspect the output impedance of a broad band amplifer with L-C low pass 
filters and transformer matching stages (possibly even feedback, 
feedforward, stabilisation, etc ) does transmission line stuff and is not 
just like a resistor in series with a zero source (Thevenin).

The heavy weights have been arguing about this for quite a while and I've 
seen magazine articles on the subject.


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