Hello Stefan,
Good SNR at 3.5 km on the 1110 km band makes this a noteworthy day!
During your future SLF pre-tests, and in the future tests that you mentioned with the ground loop transmitter, will you be using the E-field tree receiver?
I’ve wondered if near-field polarizations and E/B ratios might be different than expected with the electrically-small transmitting antenna(s) in the ULF and SLF, including near trees.
Your tree receiver SNR (~ 12dB at 424 uHz RBW, 3.5 km, 2.5ma) today seems to suggest that terrain-induced E-field/B-field transduction and polarization are not big factors; just wondering if you were planning to check your loop receiver also (but I think you mentioned that the loop would need modifications for SLF)
Your 1110 km band signal well above QRM/QRN on your grabber for the past 5 hours is a great sight.
73,
Jim AA5BW
Well, today, i did a first step into the ITU radio band 2, SLF.
Since 21:00 UTC i'm transmitting on the INV-L on 270.01 Hz. The antenna current is just 2.5 mA. The ERP is about 6 pW.
Almost nothing but anyway a trace becomes visible now on my RX on the tree in 3.5 km distance (http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html)
Of course this is a near field experiment. There, on the 1110 km band, the far field begins at a distance of 177 km.
On the transmitter site i'm using the modified 5 kV mains transformer that was used to produce 5 kV at 970 Hz. Now there is a series capacitor of about 20 uF applied to the primary winding. Together with internal reactances this maximises the peak of the fundamental frequency of the output voltage.
The goal of this first experiment is just to put the foot into this part of the radio spectrum. And to do some pre-tests, trying to optimise filter and blanker settings for future tests.
In the end i'm planning to work on that frequency from the ground loop antenna, which is still in the near field, but anyway :-)
73, Stefan
