[Elecraft] Which wattmeter do I believe?

[Larry Phipps]

I assume you are using the DL-1 as the load for all three tests, in 
which case I would have to go with the DL-1 plus DMM. The impedance 
error should be less than 5%, and the voltage measurement error less 
than that.

Larry N8LP



John Pfeifer wrote:

>Just finished building KX-1 #1207 with 30m board and ATU.  Nice little rig!
>
>After adjusting C9 on the KXAT-1 per the manual, I decided to compare the 
>power output measurements obtained via the internal power sensor, a DL-1 
>dummy load + DMM, and using my OHR WM-2 QRP wattmeter.  BTW, the supply 
>voltage is 12.5v and I substituted a 33-ohm resistor for R30.  Output before 
>I changed R30 was about 1-watt lower across the board.  Here are the final 
>measurements, as built:
>
>Band     DL-1+DMM     Internal      WM-2
>20m        2.6           3          3.7
>30m        3.7           4          4.7
>40m        3.4           4.1        4.3
>
>Which wattmeter should I believe?  I tend to think the DL-1 plus my Fluke 
>digital multimeter would give me the most accurate reading, but....
>
>Also, no matter how I fiddle with the spacing on L3, 20m output is always 
>1-watt less than on 30 and 40m.  I guess this is in line with what other 
>folks have reported.
>
>tnx & 73,
>John Pfeifer - WL7M
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