I've done some tests on VLF also, like many others on this group.
For antennas i've used a 1.5m x 2.5m 3-turn loop, a 4mx14m 1-turn loop,
and coupling to external structures (i won't disscuss this bit here :).
Using the third antenna i can receive my vlf beacon abt 750m from here.
The power was abt. 2W from a TDA2030:
http://acid.ch.pw.edu.pl/~sq5bpf/ham/vlf/20100203/vlfcapt3747.jpg
The receiving antenna was a 100turn loop in a hula-hop toy with a dia. of
90cm. This loop was tuned to resonance and amplified.
Using the 4x14m loop and abt. 40w from a TDA1562 i can receive it from
930m:
http://acid.ch.pw.edu.pl/~sq5bpf/ham/vlf/capt0706082213.jpg
The receiving antenna was a 50turn loop in a hula-hop toy with a dia. of
80cm. This loop was connected to the amplifier virtual ground (broadband
design like "easyloop").
If i remember correctly i could receive 40W into the 1.5x2.5m 3-turn loop
at about 500m.
Unfortunately i haven't had an opportunity to play with e-field antennas,
which should be much more efficient. I've noted that for b-field antennas
nearby installations (power lines, phone lines etc) can carry the vlf
signal far away (hint :)
VY 73
Jacek / SQ5BPF
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