[Elecraft] L1 vs W1 Power Reading

[Don Wilhelm]

Brian,

Unless you used a very accurate wattmeter to calibrate the W1, I would 
believe the DL1.
HOWEVER:  The formula in the DL1 manual is not correct.  8.97 volts 
measured from the DL1 properly indicates 3.44 watts.
The correct formula for the DL1 is (Vdmm + Vdiode)^2/25.  You can 
measure the actual forward voltage drop of you diode in the DL1 and 
substitute into the formula above, or assume the diode drop is 0.3 volts.

I believe an updated DL1 manual may be due with the corrected power 
formula - I submitted the power formula derivation to Bob Friess (he 
designed the DL1) and he accepted it.

73,
Don W3FPR

akiwi ham wrote:
> I recently put together a DL1 dummy load and W1 wattmeter.
>
> I have the DL1 connected to my KX1 through the W1. I have the W1 connected
> to a computer using the W1 software. I have a significant difference between
> the power reading from the W1 and the power calculated from the voltage
> measured on TP1 of the DL1 using a digital volt meter.
>
> For example:
>
> W1 reading = 4.04W
>
> TP1 volts on DL1 = 8.97V => 3.29W
>
> Is this magnitude of difference to be expected?
>
>  Bryan, Zl1NI
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