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
impedance."
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.
David
G3UNA
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