Posted by
Don Wilhelm-3 on
Dec 06, 2006; 3:48pm
URL: http://elecraft.85.s1.nabble.com/KAT2-further-Questions-tp441630p441631.html
Richard,
If your power output indication varies with frequency, then it could be that
the KAT2 wattmeter diodes are frequency sensitive.
BUT, I must ask - how do you know your dummy load is not frequency sensitive
as well, and what is the accuracy of your external wattmeter? Many
wattmeters available to amateurs are frequency dependent and the accuracy is
no better than 10% of FULL SCALE - so if your wattmeter is on a 100 watt
scale it could be incorrect by as much as 10 watts - at any power level!!
If you have an antenna analyzer, you can check the impedance of your dummy
load on all bands - and if you have the external wattmeter and the dummy
load connected at the same time, that is another potential source for error.
You can do better calibration with a known dummy load and an RF Probe than
you can with most wattmeters - just use ohms law to determine the power, but
then if you don't have an accurately known dummy load impedance, your
results will be off. Do not depend on the ads of the dummy load
manufacturer unless it is a commercial grade dummy load. Some amateur grade
dummy loads are only good enough to provide an acceptable load for the
transmitter.
We really need to know your setup details before we can comment
intelligently. I do not trust any measuring device (particularly dummy
loads and wattmeters) any further than its parameters have been verified.
Check out your measurement equipment first before attempting to fix a
non-problem.
I would not expect the KAT2 to successfully tune a 20 meter dipole to 160
meters, there is just not enough inductance and capacitance available. As
for 17 meters, it will likely depend on the feedline and its length - there
may be a very high impedance at the feedpoint and the the L networks used by
the Elecraft tuners do not do well into very high impedances.
73,
Don W3FPR
> -----Original Message-----
>
> Thanks Don for the reply. I have since found that I had installed
> R6 before
> I was suppose to so those voltages I quoted were "loaded down"
> not isolated.
> This might further explain why I do not have a left over resistor and the
> voltages being slightly low. Next issue I realize that the instructions
> state that the SWR into 50 ohm 1:1 and slightly off on higher bands. Mine
> shows a 1:1 until 20 meters 1.3:1 it continues to get worse until
> 10 meters
> is 2.3:1. I have also noticed that power control is not right. With a
> wattmeter inline with the 50 ohm load, power requested and
> indicated on the
> K2 and power read on the output don't agree and get worse as frequency
> increases. In most cases the power output is less than requested and
> indicated on the K2. I attempted to tune a "20 meter" dipole strung around
> the basement. I found the 160 and 17 meters did not tune. 15
> meters tuned >
> 3:1. The rest tuned < 2:1. Some bands (lower primarily) the power
> is reduced
> to 2 watts and tuned up. Other bands it looks like it is tuning up at full
> power. I had to wind T1 twice during the build and I am still not sure I
> wound it properly. Any more thoughts and ideas??
>
>
>
> Richard Kent K2 5296
>
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