From G3PLX:
Some small corrections to the calculation of the erp of a LORAN line...
The mean power of a LORAN transmitter is a little lower than I said. If the
published peak power is P and the Group Repetition Interval (GRI) is G, then
the mean power will be 74.88*P/G for a master station (9 pulses/group) and
66.56*P/G for a slave (8 pulses/group). For example the Lessay (G=6731)
slave transmitters are radiating 2.45 kW mean power. Thanks to DF6NM for
helping me to get this part more accurate.
To simplify the calculation derived from the spectrum measurements I showed
in my last posting, the mean erp of spectral lines around 136kHz can be
calculated as 1.155e-4*M/G where M is the mean power calculated as above.
This makes the spurii from the Lessay slaves (eg Rugby) about 42uW.
(micro-watts).
Because of the way the pulses interact, individual spectral lines may be up
to 3dB higher than this, or they may cancel out completely at some
frequencies - it would be too complicated to figure out exactly what should
be the level of each individual spectral line and the above calculation is
attempting to give an average level only.
I am still not sure I believe that we can really hear signals this low in
power!
73
Peter
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