[Elecraft] Elecraft DL1 Wideband Dummy Load

[Don Wilhelm]

David,

The 0.15 volts has to be a compensation factor for the diode non-linearity
at low power levels.
The rest of the formula is correct though - Start with the basic formula for
power V**2/R  (V is the RMS value in this formula) and manipulate it for
zero to peak voltage, you end up with ((V(0-p))**2)/2R, so since the formula
given does convert first from RMS to zero to peak voltage, then adds the
compensation (0.15), you have to have 2 times the resistance in the
denominator - just math stuff.

73,
Don W3FPR

"Life is what happens when you are making other plans"
(John Lennon wrote it in a book, Mike Cross used it in a song - I don't know
who was first)

----- Original Message ----- 

> I am having some difficulty in understanding the formula quoted on the
> DL1 information sheet for the calculation of power from the voltage
> measured at TP1, across one half of the 50 ohm load.
>
> P(watts) = (((V x 1.414)+0.15))^2)/50
>
> I wonder if someone would care to explain it?
>
> I take it that the meter reads r.m.s. and the 1.414 is to convert the
> reading to the peak value.  But what is the 0.15 for and why is the
> numerator divided by 50 when the meter is connected across 25 ohms?
>