Posted by
Don Wilhelm-4 on
Mar 25, 2009; 12:58pm
URL: http://elecraft.85.s1.nabble.com/K1-AutoTuner-KAT1-tp2532020p2532234.html
Nate,
I have trouble believing the KAT1 is not differentiating between 2.2
watts and 5 watts.
Are you certain you are reading the 'scope correctly? At 5 watts, the
peak to peak RF voltage shown on the 'scope will be 44.72 volts. You
must use a 10X probe across the dummy load for accurate results and
calibrate the probe using the 'scope's calibrator for a nice square wave
of the correct amplitude.
Actually it is easier to use a 4 watt output - that is exactly 40 volts
peak to peak deflection on the 'scope.
To quickly (and precisely) calculate the power from the peak to peak
voltage, square the peak to peak voltage reading and divide by 400 to
obtain the power with a 50 ohm load.
Now to answer your question. C9 *must* be set to the null point using a
very accurate 50 ohm load. That load must have no reactance if you are
to achieve accurate calibration results. Measure the dummy load with an
antenna analyzer if you do not know its accuracy.
After adjusting C9, and using the same accurate dummy load, adjust the
K1 power output to indicate 40 volts peak to peak deflection on the
'scope and adjust the FWD pot to indicate 4 watts on the K1. You my
have to make several interative steps until the 'scope indication and
the display agree. Expect a +/- 1 digit variation in the K1 power
display, so 3.9, 4.0 and 4.1 may all indicate a nominal 4 watts output.
dogbulter wrote:
> I recently completed the K1 with the optional KAT1 tuner. I have already aligned and tested the K1 without the autotuner installed and it works perfectly. I am trying to align the KAT1 but I am having an issue with the power calibration. I adjusted C9 to the lowest voltage, about 60mv. After I switch to CLP I make sure the output power is 5w using an oscilloscope. I then try to adjust the reading on the lCD display to match the output power but can never go about 2.2w. The only way to match the power out is to adjust C9. I know I am forgetting a small step somewhere but I am tired of messing with it.
>
> I have also cycled through all of the relay switches to ensure they work.
>
> Nate
>
>
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