Hi Paul,
Am 07.12.2016 14:50, schrieb Paul Nicholson:
About 1uW should give some hint in a hour and very significant
peak on an 8 hour spectrum.
I run a constant carrier from 13:30...7:00 UTC. On 7 UTC i will start an
EbNaut transmission for my local test: 5 chars 8K19A 80s. This takes
half a day about...
I also added a few plots and spectrograms to follow the transmission
from the tree
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
Also you can check the antenna current plot to get some more
information: http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png
BTW i put 5x 7 Ah accus there and am recording at 24 kS/s stereo to a 32
GB USB stick. The recording hast started about 15 UTC and i will drive
there (a trip of 2x 110 km!) again sunday morning to bring it back. Poor
accus, have to do that job below 0 C.
So i have more than 3 day time to run various transmission tests..
I'm plotting the signal level and noise level, visible on the grabber.
At night, the signal becomes about 10 dB stronger while the noise
increases maybe 3 dB. The antenna current is super stable however. What
could the reason be? Propagation? I wouldn't assume that.
I do not see this effect on 6470 Hz.
Update from 23:20 UTC: I found that the time server program has crashed!
:-( And it is an old PC so there are glitches from time to time.
Probably this is another reason why you don't see the faintest signal
:-( My grabber plots look quite good anyway, so maybe the problem hasn't
been so dramatic.
Now i'm watching the phase! And since 23:23 UTC it should be stable.
This may also explain the lower SNR in daylight, maybe it just has to do
with the number of phase jumps in one FFT :-(
A few things don't run as unproblematic as i would like but at least a
signal is on the air... I will sort out all problems by time...
You made a long transmission with 30mA, from 2016-06-26_13:00
to 2016-07-31_08:00, 34.79 days. No trace of the signal even
with a coherent daily stacking gain of 15.4dB. Wait 58 says
0.036 fT for your ~100nW, which should have been visible in
one day, say 8 hours.
So something is not adding up. Maybe ERP is much lower
than estimated, or the propagation near the mode 2 cut-off
frequency is more attenuated or suffering a variable phase
due to dispersion.
We will find that out! That's the interesting thing on this new land.
And i can rise the power by another 8 dB. But later...
73, Stefan
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