Posted by
alorona on
May 11, 2011; 9:13pm
URL: http://elecraft.85.s1.nabble.com/KPA-500-Output-for-Input-schedule-tp6352735p6353644.html
It's very easy to measure the 1-tone gain compression characteristics of an
amplifier. The desired result is a graph of Pout vs. Pin, with Pin on the
horizontal axis and Pout on the vertical.
So what one needs to do is set Pin to the amp, and measure Pout into a dummy
load. If you do this for several values of Pin, you'll be able to plot all of
those measured points on the graph. It will look like a pretty straight line
toward the lower Pin values, then it will flatten out (become more horizontal)
as Pin (and Pout) get higher.
The slope of the line is the gain of the amplifier.
Very often the Pin values are 1 dB apart. One dB is about a 25% increase in
power. Meaning that if you are measuring Pin in Watts, then you can set Pin to
roughly the following values:
1, 1.5, 2, 3, 4, 5, 7, 10, 13 Watts, etc.,
and measure the Pout at each value. The values should be converted to dBm before
plotting. That's all there is to it.
This is all done in CW mode. If you want to go further, you can go into SSB mode
and apply two tones to the amp (which a K3 has the ability to do) and then look
at the output of both the K3 and the KPA500 with a spectrum analyzer... but I'll
leave that explanation for another day... or it can be found on the web.
Al W6LX
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