Signal strength measurements of various LF stations by OH2LX:
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kHz Stn d,km AZI Indicated ESH2 input, dBmW
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68.9 DHJ58? 1115, 242 -105 -101 -98 -104 -98 -104 -99
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73.3 Rugby, 1825, 252, -105 -106 -105 -104 Nil -105 -105
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75.0 HBG, 1992, 226, -102 -107 -108 -104 -97 -107 -105
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77.5 DCF77, 1543, 228, -90 -94 -93 -89 -87 -93 -92
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128.9 DCF49, 1544, 228, -92 -93 -85 -94 -91 -93 -88
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138.8 DBF39, 1221, 226, -86 -92 -84 -90 -85 -91 -89
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135.8 SXV, 2490, 182, -108 -108 -105 -111 -104 -105 -107
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137.0 CFH, 5750, 295, Nil Nil Nil Nil Nil Nil Nil
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(R&S ESH2/---- 10m coax----/1:10/-----15m wire-----):
Noise level with antenna: with 200Hz IF BandWidth:
-24..-20 dB(uV), -131..-127dBmW (varies with frq, qrm, qrn etc)
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End of message of 12th June 2000, 0700 UTC, from OH2LX
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DISCUSSION: In RadCom May 2000, (p 95) "the last Word" C J Osborne,
G3XIZ writes about "Watt Nonsense" and suggests: "Ditch dBW and
use watts...". In RadCom June 2000 Peter Chadwick, G3RZP comments
under caption: "The much Maligned dBW"; G3RZP writes: "..it (dBW)
came from the use of dBm for measuring receiver sensitivity, which
originated from the radar/electronic warfare community, where
matched impedances and received powers were the major parameters
of interest ..... dBm is the power in decibels relative to 1mW,
which would be provided to the equipment if the load impedance
was 50 ohms - a lot of assumptions...".
OH2LX: Actually there is no reason to tabulate my measurements
in dBmW. I wouldn't even dream of using "received power" unless
I use for measurements a genuine MEASURING RECEIVER, an R&S ESH2.
Note: In my case approximate field strength (around 136 kHz) is:
F-s (dBuV/m) = dBmW + 127dB, e.g. -127dBmW + 127dB = 0 dBuV/m.
(have not yet attempted to calibrate it around 70-80 kHz).
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V.K.Lehtoranta, OH2LX, POBox 50, FIN-05401 Jokela, Finland
------ Tel: +358-9-4173965 ---- Fax: +358-9-4173961 ------
E-mail: [email protected] - alias: [email protected] & [email protected]
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