Wolf:
That would be another way to get a calibration, so long as we also knew the
emrp of DCF39. If you are close enough to receive surface wave from DCF39
and surface wave from Sylt, then a ratio of the DCF39 carrier level to the
level of a typical Sylt LORAN line (at midday) could be used to give the
emrp of the LORAN line. WE can estimate the path loss from the distance
within a few dB so long as the both paths are over similar type of ground.
But Dave G0MRF also sent me a nice spreadsheet of some measurements which
were made at Rugby when the LORAN transmitter was installed. This is a
record of the classic USCG measurement to confirm that only 1% of the energy
is outside 90-110kHz. This spreadsheet seems to be a chart of the readings
of a spectrum analyser which is changed in 2kHz steps between 70 and 130kHz,
measuring the levels in a narrow bandwidth (<2kHz?) from an antenna-current
monitoring point. From this I can apply an F-squared factor to calculate the
power spectral density. I have to guess the shape of the curve from 130kHz
to 136kHz.
This tells me (if I did it right) that the spectral density at 136kHz is
about 47.5dB down on the spectral density at 100kHz. The problem now is that
I don't know how to convert this to the mean level of a single spectral
line - I need to know the relationship between the published power of the
transmitter (presumably the peak pulse emrp) and the spectral density (mean
power/kHz) at 100kHz.
Anyone have any ideas? Maybe this can be measured off-air, or we can figure
it out from published info.
73
Peter G3PLX
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