[Elecraft] K3 - internal TX PWR meter accuracy?

[Ken K3IU]

Hi Glenn:

Without claiming accuracy to any traceable standard, I just fired up my 
trusty old 100 MHz HP 1740A O-scope, calibrated the display to the 
built-in 1 volt calibration standard, and measured the P-P voltage into 
a 51 ohm resistance (no measurable reactance). At 100 watts commanded 
and indicated on the K3 (#202), I measured about 202v P-P. That 
translates to about 100 watts. With the K3 set for 120 watts, I measured 
about 220v P-P, which is about 119 watts. With the K3 set for 90 watts, 
I measure about 192v P-P which is about 90 watts.

So... I would say that the K3 does a pretty good job in producing the 
commanded power.

73,
Ken K3IU
Portsmouth, RI

ON4WIX wrote:
> Hi group,
>
> I was just wondering if anyone has done TX power measurements with 
> precision measuring gear and compared these measurements against the 
> K3's internal indication of the output power?
> Just curious here. The K3/100 is advertized as a 100W transceiver (or 
> should that be "100W class"?) and the power control on my unit goes up 
> to 120W. With the PWR cranked up to 120W the K3's bargraph meter does 
> indeed show 120W output. The only external measuring tool I have is 
> one of those cross-needle meter (Daiwa CN801H) which I know displays 
> the output power a few % low into a known good dummy load but I've 
> never been in a position to accurately determine just *how much* low. 
> The Daiwa's spec sheet mentions 10% FS excursion error so that would 
> translate into a 20W uncertainty at the 200W meter scale setting.
> Any input would be much appreciated. I know that there will be no 
> discernible difference on the receiving end when going from 90W to 
> 110W but as they say... inquiring minds want to know.
>
> 73 es tnx
>
> Glenn ON4WIX
> K2/100 #5361
> K3/100 #192
>