Hi all,
Since sunday 13 UTC i'm running a carrier on 2.970000000 kHz. The ERP is
100 nW. The antenna current is 30 mA.
The signal appears at up to 30 dB SNR in 424 uHz on my 3.5 km distant
remote grabber,
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
I've done a successful test with a portable active E field receiver: abt
15 dB in 3.8 mHz in 4.5 km distance in a quiet location:
http://no.nonsense.ee/qth/map.html?qth=JN49IK66KU&from=JN49IK00WD
So 4.5 km is the new distance record on that band :-)
This was just for testing the receiver, which still needs some more
input signal get get it's full sensitivity.
The actual next goal is 50% of the far field border, i.e. ~ 8 km distance.
Paul, if you are reading this: It may be worth to try to integrate the
overall transmission time into one peak. I will continue to run the
carrier. So far, these 72 hours are not enough to get a peak i estimate.
But with one or two weeks integrated in one peak?? Maybe... :-)
The QRN is much lower relative to 8.27 kHz, so this may help.
There is some QSB on the 3.5 km path to my grabber. I've watched the
phase stability over that path: It is constant, as expected:
https://dl.dropboxusercontent.com/u/19882028/ULF/2970%20Hz%20RDF%20stabile%20Phase.jpg
Now my assumption is that the signal level drops when the forest is wet,
although it is a loop antenna! That also means that my RX sensitivity on
2.97 kHz is limited by the RX, not by the band noise. So the actual SNR
could be better...
A photo of the TX transformer/coil in it's final position:
https://dl.dropboxusercontent.com/u/19882028/ULF/20160623_234516.jpg
The 8 km distant ULF detection test is planned for this weekend. If it
works well, i'm doing a second test in EbNaut in the same location :-)
73, Stefan
|
