[Elecraft] Power Readout Discrepency

[Ron D'Eau Claire]

Even so, Don, within the capability of the K2 to provide the RF and =
within
the operating range of the Power Control circuitry, the Power metering
circuit in the basic K2 will provide the requested power to a =
non-reactive
50 ohm load within 10 or 20 percent. That's as good as most "Ham type"
wattmeters will indicate anyway. Elecraft spec's it as within 10% at 5
watts.=20

As I commented earlier, my K2 - when set at 10 watts using the POWER =
control
- will deliver from  9.7 watts on 160 meters and a high of 11.5 watts as =
one
works across the bands to 10 meters with the rig terminated in a good =
50-ohm
dummy load. Of course, that's the combined error of  the K2  and =
external
wattmeter. I used two external power measuring devices that were within =
4 %
of each other across that range.

You are absolutely right that, in actual practice, the K2 almost never =
sees
a highly-accurate non-reactive 50 ohm load feeding an ATU or antenna. =
That
will cause errors in the power indication. Most SWR meters will show a
"perfect match" over a range that introduces significant errors in the
termination for the purposes of making an accurate power measurement =
using a
simple RF voltmeter circuit like that in the basic K2.

Ron AC7AC

-----Original Message-----
I trust you are not confusing the "power requested" indication that is
displayed when you turn the POWER knob with the actual power output.  =
The
actual power output may fall quite short of the requested power because =
of a
number of things - including the actual load impedance - the RF detector
arrangement in the base K2 is quite unsophisticated and great accuracy
should not be expected from it.

If you have installed one of the Elecraft automatic tuners, the story is
quite different again because the tuners include a real wattmeter (which =
you
can calibrate) rather than the simple RF detector included in the base =
K2.

73,
Don W3FPR