[Elecraft] K2 power meter/wattmeter question

[Vic Rosenthal]

Mike Monger wrote:

> How accurate have you found the internal power meter/wattmeter to be on the
> K2???

The wattmeter in a basic K2 (without the KAT2 or KPA100) just measures the RF 
voltage and computes the power.  Therefore, the accuracy is highly dependent on 
having an accurate 50 ohm resistive load.  The KATs and the KPA contain 
directional wattmeters, which are more accurate if the load varies from exactly 
50 ohms.  Of course, you calibrate them when you build the rig, and the accuracy 
depends on what you use to calibrate them!

Also, as someone else has pointed out, the accuracy of a wattmeter with a 200 
watt scale is quite poor at the low end.  Bird rates their meters at 5% of full 
scale, so if the Tentec is the same then it could be off as much as + or - 10 
watts!  Because of the nonlinearity of diodes in the low part of their curves, 
usually such meters are worse at the low end.

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.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco