[Elecraft] K2 power meter/wattmeter question

[vze3v8dt at verizon.net]

I have the OHR WM2 and a Bird 43 with a 50W 2-30 MHz slug.  Both the Bird & the OHR showed about the same power at 10W out of the K2 on all HF bands into a good 50 ohm non-inductive load.  Power settings at various power levels from 0.1 to 10W going through the OHR WM2 show pretty good results across the whole range.  I haven't measured it on any lab grade power meters that I have at work yet, because frankly, it just doesn't matter.

I notice power settings that appear to be off by as much as 0.5W at 5W set power on the K2 but that is going through an external antenna tuner to the antenna.  I think the "error" is more in the slight VSWR mismatch causing measurement problems.  The power readings are only accurate into a non-inductive 50 ohm load.  

If you convert your measured power to the set power ratio to dB it is likely a very small amount.  For instance if the apparent measured power is say 6W and the K2 is set for 5W, this power difference is only 0.8 dB.  For "ham" requirements this is likely fine, but for "lab" or "professional" measurements this may not be acceptable.  

An old saying "Don't sweat the little stuff" may apply here.

Mark, NK8Q
K2 #4786

>
>The OHR WM2 is a good and accurate QRP wattmeter.  A calibrated scope or DVM 
>with RF probe and a known accurate 50 ohm load can also be used.
>
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