[Elecraft] KX3 Power OUTPUT and WATTMTR value

[Don Wilhelm]

Ron,

Yes, the KX3 power output will change with the setting of the WATTMTR 
value - that is a calibration setting.

The KX3, like the K3 and K2 before it control the power in a closed loop 
system.  The power knob presents the requested power to the 
microprocessor, and that is compared to the actual power output 
indicated by the wattmeter at the output of the transmitter.  Drive is 
adjusted to make them equal.

The KX3 WATTMTR menu parameter is a calibration parameter.  It can be 
adjusted to make the power output of the KX3 conform to whatever trusted 
power meter you may have available.  Before straying too far from the 
default value, be certain your external wattmeter is accurate at the 
power levels you are working with.  Many amateur grade wattmeters are 
speced at 20% of the full range value.  That means that on a 20 watt 
scale, the error can be up to 4 watts - and that applies to any point on 
the scale.  Those wattmeters with a digital readout (rather than an 
analog meter) are usually a percentage of the actual reading rather than 
the full scale, but refer to the specifications for your wattmeter for 
details.
In other words, at low power levels, be aware of what your wattmeter is 
telling you - it may be quite different than the actual indication on 
the meter.

73,
Don W3FPR

On 2/25/2014 12:22 AM, Ron wrote:
> Has anyone else observed that the Power Output of the KX3 is changed by the
> setting of the WATTMTR value?
>
>   
>
> For example on 20M, CW mode into a dummy load, ATU in bypass.  Power set at
> 10 watts, I measure 6.8 watts with a WATTMTR setting of 1.0.  But with a
> value of .070, I measure 9.9.  The factory sets it at 0.84  I measure 8.2
> watts at that value.
>
> At a setting of 12 watts I measure a power out of 8.2 watts at a WATTMTR
> setting of 1.00 and 11.5 watts with a WATTMTR value of 0.70.
>
>