Tonite i also did (again) measurements of DCF39.
I did a recording of the soundcard input of my LF grabber PC, so the
signal was coming from the homemade E field probe, 35 m above ground in
Heidelberg.
It was a silent night.
At http://dl.dropbox.com/u/19882028/LF/LF_wide_in_1Hz.png one can see my
DCF39 received signal and its ugly sidebands. The displayed SNR is about
80 dB in 1 Hz. This is without noise reduction, so connected to L1. Note
that the background noise is 20 dB below the LF amateur band (analog
filters in front of the mixer). So does this mean i would receive DCF39
at 100 dB SNR in 1 Hz?? Well, it was night time...
Anyway my RX seems better than i expected, unfortunately ;-)
Something must be wrong anyway. I expect DLF causes problems when
running 500 kW at daytime.
Have to repeat the comparison with the loop, nulling out DCF...
73, Stefan/DK7FC
Am 09.08.2011 23:58, schrieb James Moritz:
Dear Stefan, Minto, LF Group,
No TX this evening here, I'm afraid, but I took the opportunity to
make rough measurements of the field strengths of G3KEV (12uV/m),
DK7FC (1.9uV/m) and HB9ASB (0.7uV/m) - see the attached screen capture.
As you can see, these are all "O" copy signals here. KEV is quite a
strong audible signal here as usual - DK7FC and HB9ASB look a bit
weaker than they actually were - this screenshot was taken with my
loop oriented approx. N-S to measure Mal's FS; with the loop oriented
E-W Stefan and Toni were both several dB stronger. The QRN level was
fairly low here for the time of year, and the band noise was dominated
by Loran C with the loop aimed N-S, and sidebands from DCF39 with the
loop E-W.
Earlier, I repeated PA3BCA's signal-to-noise measurement on DCF39 -
The SNR of DCF39 was about 82dB with the 0.5Hz FFT noise bandwidth. My
location IO91vr is a bit further from DCF39, so I would expect the SNR
in PA to be a few dB higher under similar conditions. The field
strength of DCF39 was about 3mV/m (several dB higher than the daytime
level I have measured in the past), making the noise floor about
0.24uV/m in 0.5Hz.
Cheers, Jim Moritz
73 de M0BMU
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