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Re: [Amps] Transceiver Output Impedance

To: "David Cutter" <>, <>
Subject: Re: [Amps] Transceiver Output Impedance
From: "jeremy-ca" <>
Date: Sun, 9 Mar 2008 11:18:28 -0400
List-post: <">>
I remember reading a letter from Kenwood about 20 years ago that stated that 
their SS PA stages were designed to operate into 25-75 Ohm loads since 50 
Ohm cable was not a world wide standard.

Ive been operating my TS-940's ( and TS-930's before that) into 75 Ohm loads 
since the late 80's with no difficulty and no power foldback. I do not use 
an antenna tuner, built in or external.


----- Original Message ----- 
From: "David Cutter" <>
To: <>
Sent: Sunday, March 09, 2008 8:18 AM
Subject: Re: [Amps] Transceiver Output Impedance

> 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
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