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
