Hi Luis,
Am 05.06.2019 22:58, schrieb VIGILANT Luis Fernández:
Hi
Stefan, VLF
>Don't
expect better results from a larger antenna at the same location
Not the same location. I'm using my Tx antenna in Benidorm
(IM98wn). My grabber runs in Albir, another location at 7km at IM98xn
Ah, RR.
Finally used a simple audio transformer to connect the vertical
LF resonant antenna to the PC audio card
And results are quite interesting. This is the 24KHz VLF band in
a 20 minutes spectrogram
Yes, looks much better than the other antenna. I can see sferics for
the first time there, which is a good step. The LF resonance will have
no real effect. So the audio transformer is on the roof and then you
lay out a long cable which is then connected to the soundcard in the
shack? The cable is floating at the transformer end?
Maybe you can use that signal for some time to generate a slower
spectrogram covering 0...24 kHz, with better brightness/contrast
adjustment. This would give a better impression about the sensitivity.
If you disconnect the antenna, how much (in dB) does the noise floor
drop then?
The most important is that QRM from lift motors variators is
produced just in a few frequencies, not wipping
all the band. You can see the elevators activity as signals
around 16KHz, 15KHz, 10.5KHz and strong at 8 and
around 5.5KHz
Yes it is possible to build a special filter that blanks these small
frequency ranges. This will improve the noiseblanker performance.
During the 20min there was a sudden reduction in background
noise. This is not due to modifications in my
settings, but real QRM stopped. Has to investigate why it
happens.
Yes, it would make a big difference. Maybe a bad ground contact
somewhere. A long-time spectrogram may help as well.
I made a detailed spectrogram around 8KHz
Hm, it does not tell to much but it is promising. Also, a spectrogram
running at 1 pix/min would give a better impression.
Fortunately the offending signals are concentrated on 7700, 8000
and 8300Hz. So 8270 with high integration will be out of the
elevators interference, which is a very good news :-)
I need a signal. And connect the audio to 1pps
Yes, PPS must be. The, maybe you can even try to receive a trace of
ZEVS.
Good luck.
73, Stefan
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