Hi SLF,
Last afternoon it was sunny and relatively warm. I spent 2 hours on the
tree to improve the E field ELF...VLF antenna by increasing the probe
capacity from ~ 10 pF to ~ 40 pF. However it is hard to rise the
effective height of the antenna when sitting on a tree, sourrounded by
trees.
My local transmission on 80.005 Hz is helping to see the difference.
Not only the signal level but also the S/N seemed to rise a bit. I'm
now getting up to > 20 dB SNR in 424 uHz FFT bin width over that 3.5
km path.
Since 4 UTC, an EbNaut transmission of 45 characters is running. It
will take almost 14 hours to send. I'm very optimistic that it will
work.
73, Stefan
Am 23.11.2018 10:21, schrieb DK7FC:
Dear SLF friends,
A new step forward towards DC: Since yesterday 22:30 UTC i'm TXing a
carrier at 80.005 Hz. That's the 3750 km band, where
the far field begins at a distance of 598 km.
The antenna voltage is just 5 kV and i'm getting 1.2 mA antenna
current, giving an ERP of 20 fW (2E-14 W).
The voltage is even higher than in my recent experiment on 270 Hz,
anyway the S/N is lower, indicating that my RX lacks of sensitivity.
Indeed this experiment helps to estimate the lack of sensitivity. Looks
like i'm missing about 10 dB on that frequency. Anyway the signal is
making the path of 3.5 km to my tree grabber, as usual shown at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html.
Not
a big distance but still well beyond most garden fences!
The signal leaves a barely visible trace in the ZEVS window which is
running at 3.8 mHz FFT bin witdh. Unfortunately ZEVS is off the air
since a week or so. actually i wanted to transmit side by side with
ZEVS, of course a bit deeper even.
>From a quiet period at night, i calculated the SNR of a 1 hour carrier
period using vlfrx-tools: carrier S/N: 16.83 dB in 277.8 uHz,
-18.73 dB in 1Hz
For the crazy homebrewers i'd like to share that website where i
ordered the HV-transformer,
http://www.hosin.de/Specials/HV-Trafo/hv-trafo.html
A nightmare for all
safety-fetishists! For the completeness it must be mentioned together
with that page: http://kurts-werkstatt.de/hv-trafo.htm
73, Stefan
|
|
