|Subject:||Re: LF: RE: The next experiment on 970 Hz - Cracked the far field border below 1 kHz|
|From:||Markus Vester <[email protected]>|
|Date:||Sun, 30 Sep 2018 21:15:49 -0400|
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congratulations also from my end! The fact that you did receive the signal well on one loop but not on the E-Field remains a big riddle.
One thought just crossed my mind: The Rhine river might behave as a large conductor, extending South-to-North more or less in the middle between the antennas. There are probably also railway and electric power lines running along the valley. At this frequency, magnetic fields are penetrating deeply into the ground, and might encircle and magnetically couple to this conductor from either side.
One question is whether the H-field is stronger than expected or the E-field is too weak. This might be answered by calibrating the TX and RX antennas and measuring absolute levels. The loop area (or "effective depth") of the TX antenna might be obtained in receive mode by comparing induced voltage with a small test loop, using manmade VLF signals or spherics at different frequencies and extrapolating to 970 Hz. ZEVS might provide another data point (if it's azimuth is not too far off the maximum from the earth antenna).
Von: hvanesce <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Mo, 1. Okt 2018 1:32
Betreff: LF: RE: The next experiment on 970 Hz - Cracked the far field border below 1 kHz
Congratulations! A great milestone for many reasons.
Amazing to think of far-field at that frequency without tons of antenna; a credit to design, test planning, and test execution.
Below 2 KHz is new territory for many reasons including markedly different sky propagation and changing earth propagation which also affects the character of noise*.
Your (more than) year of considerable effort toward this goal probably kept many on the edge of their seats, me included, I’m celebrating.
In free space the electric field at a receiving antenna 0.18 wavelengths away from a transmitting loop antenna should be very good compared to the magnetic field at the same receiving location.
But for a ground loop transmitting antenna at 970 Hz I wonder if anyone knows which field (E or B) and which polarization (theta and phi) predominates at a receiving antenna near the ground at 0.18 wavelengths distance. A very interesting topic and perhaps your E-field (monopole) and B field (loop) receiving antennas have provided another milestone in this respect: perhaps a first documented data point for E vs. B at any polarization, near 0.18 wavelengths (an interesting distance on its own) from a ground-loop transmitting antenna at 970 Hz?
Another fascinating realm now opened, much appreciated.
*(noise characteristics including noise E strength vs. B strength vs. noise polarization vs. distance from noise source vs noise-source-type could be interesting at 970Hz)
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