Rik,
I made a somewhat similar caluclation last week comapring Peter, DF3LPs
signal with DBF39. I used my MV 61 Selective Level Meter that has the
ability to measure voltages between -130 dBm and +20 dBm with a accuracy of
about 0.1 dB (if calibrated). I did not calibrate it, however, for
comparison measurements it should be ok to compare the relative voltage
levels.
Peter has a signal of -116 dBm, equivalent to 0.35 uV at 75 Ohm. My minimum
noise floor is -130dBm during the day, somewhat more at night.
DBF39 has a signal of -46 dBm, this is about 1.12 mV (with less than 0.5
dB QSB).
The transmitter in Burg has a RF power of 50 kW and uses an antenna that is
210 m high. If I assume, that this Antenna has a power loss of 3 dB
compared to a full-wave 1/4 lambda groundplane, I can assume that this
transmitter has a radiated power of 25 kW ERP.
The transmitter in Burg is only 125 km away from my qth, DF3LP is 212 km
away. If I assume that the field strength is reduced at the power of the
distance, 1.7 times the distance is equivalent to about 9 dB.
Adding those 9 dBm to Peter's signal, I come to a difference betwen power
levels of DF3LPs and DBF39s signal of 60 dB.
Using the 25 kW ERP as a basis, Peter's signal is in the vicinity of 25 mW
ERP. I don't know Peters real ERP but I thought it was more. I assumed
already 35 mW for my signal which is definetely weaker than Peter's wignal.
I will continue to record relative voltage levels and see what I come up
with.
Best 73
Geri, DK8KW (W1KW)
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