Basic Calibration to convert dBu or dBm readings taken with my receiving equipment into dBµV/m:

Following some instructions given by Dick, PA0SE, I have made a 1 m
Diameter loop (for deteils see below) from a solid copper pipe and took
some very basic measurements. The comparison of taking the measurments
in my shack or out in the fields is marginal.

I measured the voltage of DCF39 to be -86.9 dBu which is equivalent
to a voltage of 35 µV

(0 dBu=0.77V, so -86.9 dBu=20*log(35µV/0.775V)).

From the equation (valid for 137 kHz):

At the same time the signal strength of DCF39 with my regular 18m high
umbrella antenna was

This value equals to

For my antenna system and the signal strength given in dBu,
add ** 108.1 dB** to achieve values in