Dear LF Group,
I was able to compare noise levels before and after the Rugby Loran signal
came up this morning (some time between 0600 and 0715, so tallying with what
Alan and Laurie saw). Before Rugby started up, the band was about as quiet
as it gets, with only a small amount of weak QRN. With a loop antenna
aligned to null out the Lessay Loran, (and so lined up nearly directly on
Rugby at my QTH) the noise level in a 300Hz bandwidth in the CW part of the
band rose about 15dB, to roughly 15dBuV/m. The Lessay noise was about 9dB
below the Rugby noise, so, if using a non-directional antenna, the noise
level here has been degraded by about 9dB. If I use a loop ant to null
Rugby, the noise level is basically that due to Lessay, about 6dB above the
natural noise floor. Up to now, I have been able to null out Lessay and so
"enjoy" essentially the natural background level, so whatever I do, the
noise situation has substantially worsened. Having had the 73kHz "growler"
to live with, and now Loran, Rugby Radio really seems to have it in for LF
amateurs!
I also made a rough measurement of the Rugby Loran field strength at 100kHz
- in a 3.1kHz bandwidth it is about 3mV/m RMS, which amounts to about 5kW
mean ERP at 150kms distance - of course, the signal bandwidth is wider than
this, so the total mean ERP is probably 2 - 3 times this. Anyway, the PEP
will be much higher due to the pulsed nature of the signal.
Cheers, Jim Moritz
73 de M0BMU
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