[Elecraft] Higher SWR When Using Amp.

[WILLIS COOKE]

Mark, when you tune your amp you are reading the input impedance of the amp SWR, 
not the antenna SWR.  The only way that your external SWR meter and the 
transceiver SWR meter should match is if the external meter is between the amp 
and the transceiver.  Even then, the SWR meters available to us are not 
precision instruments and are usually 5 to 10% of the max reading, so a 2kw watt 
meter could read 200 watts in error and still be in tolerance for an inexpensive 
meter.  The better meters could be 100 watts in error, so the error can equal or 
exceed the output of the transceiver.  If the 1.6 bothers you, you can adjust 
the input impedance matching circuit of the amplifier and perhaps reduce it, or 
you can activate your antenna tuner on your transceiver if you have one.  You 
can also expect the SWR to change some as you tune your amp.  If you have an old 
amp from the tube final days when the transceivers all had a pi network to match 
the amp, such as my Dentron Clipperton L, you may not even have an input 
matching circuit.  I use the tuner in my K3 to match the input of the 
Clipperton.  I don[t think you have anything to worry about.
Willis 'Cookie' Cooke 
K5EWJ 




________________________________
From: "pastormg2 at verizon.net" <pastormg2 at verizon.net>
To: elecraft at mailman.qth.net
Sent: Mon, November 15, 2010 5:43:49 AM
Subject: [Elecraft] Higher SWR When Using Amp.


I have noticed when I fired up my amplifier on 40 meters that the SWR reading on 
the K3 when I tune up is higher then when I tune up on standby.  But what is 
really odd is on my External Wattmeter the SWR is the same when the amp is 
active versus standby. On standby my SWR on 40 meter SSB is 1.0 to 1.  When I 
tune the Amp it goes up to 1.6 to 1.  I realize that it isn't that high but just 
would like to know if there is an explanation as to why this occurs.  Mark KB3Z
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