[Elecraft] KPA100 Metering?

[Don Wilhelm]

Fred,

Yes, the KPA100 (and the KAT2 and the KAT100) contain a directional coupler
type wattmeter to indicate the forward power and the SWR.  These wattmeters
remove the necessity for operating the K2 into a 50 ohm non-reactive load in
order to obtain power accuracy.  The forward power output of these
wattmeters is used to control the K2 power output as well as display it on
the LED (and on the LCD during TUNE).

These internal wattmeters need to be calibrated with some external reference
power metering if they are expected to be accurate.  I measure the RF
Voltage across a 1% precision 50 ohm non-reactive dummy load for the
calibration, and I feel I can calibrate the wattmeter to within 5% using
that method.  Many wattmeters available to hams are simply not that
accurate.  Even the Bird specs its accuracy at 5% of full scale ONLY after
proper calibration - and with a 100 watt slug, that means the power reading
can be up to 5 watts off at any power level.  Know your instruments and know
just how much to trust what they tell you.

73,
Don W3FPR


> -----Original Message-----
>
> I saw a reference to a "wattmeter in the KPA100"?
>
> Does the K2's "KPA100" option, include a wattmeter,
> beyond what metering is now present in my K2's
> relative reading LED multi-segment indicator?
>
> What comes with the KPA100, in this area?  If I
> bought the KPA100 option, for my K2 - could I get
> a accurate indication if I'm putting out 10watts,
> 38 watts or 100 watts?  Or if the SWR presented to
> the KPA100 is 1:1 or 11.6:1?
>
> I'm really trying to decide whether to bite on
> the KPA100 higher-power K2 option.
>
> Thanks,
> Fred N3CSY