[Elecraft] K2 power meter/wattmeter question

[W3FPR - Don Wilhelm]

Mike,

The K2 internal RF metering is quite accurate - BUT it depend on having a
precise 50 ohm non-reactive load.

The wattmeters built into the KAT2, KPA100 and KAT100 remove the dependency
on a 50 ohm resistive load, but need to be properly calibrated first.

Many (IMHO most) external wattmeters are less acurate than the internal K2
metering, particularly at low power levels.  A typical specification for
them is 20% of the full scale reading, and on your 10 watt scale, that is a
2 watt error.

In addition, you may not be setting the tuner for a true 50 ohm resistive
load to the K2.  If you have an antenna analyzer, you can do an experiment -
tune the antenna as normal and then disconnect the coax from the K2 and
measure the impedance.  I will venture to guess that it will not be 50 ohms
resistive unless you were quite lucky.  Even in bypass mode with a dummy
load on the far side of the tuner, you will likely see something other than
a 50 ohm reactive load at the input side.

While you have the antenna analyzer out, check your connecting cables too,
they can become lossy and produce strange results, and deserve to be checked
every now and then.

73,
Don W3FPR

> -----Original Message-----
>
> How accurate have you found the internal power meter/wattmeter to
> be on the K2???
>
> I ask this because there is a large difference between what I set
> the power for, on the K2, and what it displays  as compared to
> the external meter (contained in a Ten Tec tuner, scale 0 to 200
> watts, first division being between 0 and 10 watts).  To get a
> half scale reading between 0 and 10 watts (5 watts) on the Ten
> Tec  I have to set the K2's power level to over 8 watts.
>