http://elecraft.85.s1.nabble.com/K2-100-Power-investigation-tp458672p458682.html
Understand. I did pick up the DL1, and check the readings. They were
along the lines of what I experienced with the MFJ. But I could not
read it at a higher power, as it is only a 20w dummy load. But it
jibed with what I was seeing. I will get further readings with it and
> Dave,
>
> I cannot really give you a quick positive answer - the real answer is
> "it all depends". To give a positive answer would require that you
> operate into a dummy load which is 50 ohms non-reactive at all
> frequencies in question. One can measure the dummy load with an antenna
> analyzer - expect to see 50 + j0 at all frequencies of interest for
> reliable and repeatable results.
>
> I do not generally trust any wattmeter (including an uncalibrated Bird)
> to provide any greater than 20% of full scale accuracy. If the full
> scale reading is 100 watts, then the error can be as great as 20 watts
> at any point on its scale. A properly calibrated KPA100 wattmeter can
> do better than that.
>
> I find that with a good 50 ohm dummy load and an 100 MHz oscilloscope
> with a 10X probe (probe rated for 100 MHz), I can calibrate the KPA100
> wattmeter to less than 5% accuracy on bands below 20 meters - at higher
> frequencies, the 'scope and probe rolloff will indicate lower than
> expected results. But I can state that once calibrated, the KPA100
> power calibration can be trusted to greater accuracy than the
> run-of-the-mill wattmeters.
>
> Using a good 50 ohm non-reactive dummy load and measuring the RF voltage
> across it:
> At 4 watts, the Peak to Peak RF voltage will be 40 volts.
> At 10 watts the p-p RF voltage will be 63.25 volts
> At 40 watts, the p-p RF voltage will be 126.5 volts
> At 100 watts, the p-p RF voltage will be 200 volts.
>
> My dummy load is a heat-sinked Caddock MP9100-50.0-1% resistor rated at
> 100 watts with zero length leads that has been measured flat at 50 ohms
> up to 60 MHz.
>
> Up to the frequency limits of my oscilloscope, I trust my dummy load and
> the peak to peak voltage measurement to provide more accurate power
> measurement than any wattmeter available. I find that, after
> calibrating with these tools, the typical KPA100 power indications are
> within 5% of the actual power output.
>
> I can also say that the TelePost LP-200 (and I assume the LP100) will
> also produce power readings which are within 5% of the actual power
> after proper calibration. I cannot make such statements about the
> accuracy of the more common wattmeters which spec their accuracy as a
> percentage of the full scale reading. A Bird with a 100 watt slug that
> has been recently calibrated will have an accuracy of 5% of full scale,
> which is a 5 watt error anywhere on the scale - so a recently calibrated
> Bird with a 100 watt slug will indicate anywhere between 5 watts and 15
> watts for an actual power of 10 watts. One can do better with a
> precision 50 ohm load and a 100 MHz oscilloscope.
>
> OK, that is my wattmeter rant for this month!!!
>
> 73,
> Don W3FPR
>
> David Wilburn wrote:
>> After trying unsuccessfully to get email to take data in tabs, I ended
>> up just putting the information on my website. Sorry for the trouble.
>>
>> I was playing with an assortment of power meters, and noticed my K2
>> was reading lower than I expected. The closes things I had to a
>> gauge, was an IC-703+ that had just been to the shop, and repaired,
>> thus I felt it was likely to be putting out 10w.
>>
>> When I compared a Bird 43 with an element I picked up on line, and one
>> that came with it, it read a bit low. But when I used an MFJ949e, it
>> was right on. Gotta run with what I have.
>>
>> So I checked out the K2/100 at what it said was 10w/53w/111w (Full
>> Power). And I got the results, that are displayed here;
>>
>>
http://www.k4dgw.com/k2.html>>
>> The 10w settings seem a little bit more dispersed than I would have
>> thought. The 10m, 12m & 20m 53w settings seem a bit low. Then at
>> what the rig says is 111w/Full Power, the rig seems even lower.
>>
>> Do I need to go back through and run the power calibration, or should
>> I start troubleshooting?
>>
>> I have a KAT100, that was powered down, and the power was taken out of
>> the back of the K2/100.
>
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