K2 Power Calibration

[Cathy James]

I have been playing around with the K2 since finishing it.  No
successful QSOs yet, but I blame the bands, my limited operator skills,
and limited operating time rather than the rig.

However, while testing, I noticed that my MFJ-941E claims that the K2 is
putting out about 10 W on 40 meters when the K2 power setting reads 5.0,
and the -941E claims 5 W out at about 3.3 on the K2 display.  I don't
know which one to trust, since the -941E is certainly not calibrated to
any significant accuracy.  Still, I have generally found the -941E's
reading to correlate well with the published power from my other rig.

Any ideas as to why the K2 power display on the LCD could be that far
off, if indeed it is?

--Cathy, N5WVR


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[Don Wilhelm-3]

Cathy,

First I am going to make an assumption (I know that is dangerous!).  I would
believe that you are operating into an antenna rather than a good 50 ohm
non-reactive dummy load.

Now, if your antenna impedance is lower than 50 ohms, the wattmeter will
report the power correctly, but the base K2 will indicate according to the
RF Voltage it sees at its output, and since the impedance is low, the
voltage will also be low, and the K2 firmware will compute the 'power'
assuming that the load is 50 ohms.  So bottom line, if your antenna load is
anything other than 50 ohms resistive, the base K2 will not report the power
correctly.

Adding either the KAT2, KPA100 or KAT100 options will include a proper
wattmeter in the K2 system and the display will indicate the proper power
(if the wattmeter is calibrated properly), but the basic K2 uses only an RF
Probe type detector and reports the 'power' based on the assumption that the
load is 50 ohms non-reactive.  Try a dummy load and if you see a major
discrepancy, you can blame the interconnecting coax or the wattmeter - the
basic K2 power indication is quite correct when the laod is a 50 ohm proper
dummy load.

73,
Don W3FPR

> -----Original Message-----
>
> I have been playing around with the K2 since finishing it.  No
> successful QSOs yet, but I blame the bands, my limited operator skills,
> and limited operating time rather than the rig.
>
> However, while testing, I noticed that my MFJ-941E claims that the K2 is
> putting out about 10 W on 40 meters when the K2 power setting reads 5.0,
> and the -941E claims 5 W out at about 3.3 on the K2 display.  I don't
> know which one to trust, since the -941E is certainly not calibrated to
> any significant accuracy.  Still, I have generally found the -941E's
> reading to correlate well with the published power from my other rig.
>
> Any ideas as to why the K2 power display on the LCD could be that far
> off, if indeed it is?
>
> --Cathy, N5WVR
>
>

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