ARLA/CLUSTER: Transmissões transatlancias em VLF (29,499 kHz)

[João Costa > CT1FBF]

 Transatlantic 29 kHz VLF transmission

In his blog *Roger Lapthorn G3XBM* reports that both the 29.499 kHz
Transatlantic transmissions have been heard in the UK

Roger writes:

In recent weeks a number of amateur tests have been running from the USA to
Europe around 74kHz and at 29.499kHz using several hundred watts to large
antennas.  74kHz has been well copied, but the surprise is 29.499kHz with
SWL Paul Nicholson and Marcus DF6NM, and others, copying the test signals,
for example,  at over 15dB S/N in  424uHz bandwidth.  As far as I know,
these 29.499kHz VLF signals are the first amateur VLF ones to span the
Atlantic - fantastic results by well equipped stations using suitable RXs
and good software.

The ARRL report:

Bob Raide, W2ZM, was transmitting on 29.499 kHz under a Part 5 Experimental
license, WH2XBA/1. His very slow-speed (QRSS) CW signal was initially
detected in the UK just before 0000 UTC on March 3 by Paul Nicholson, an
SWL, and later by Mike Dennison, G3XDV, and Markus Vester, DK6NM, in
Germany. Nicholson also copied a 29.501 kHz transmission from Dex McIntyre,
W4DEX, in North Carolina, operating as WH2XBA/4.

His transmitter has a 3CX3000A7 tube in the final, running grounded grid
and generating 800 W. The effective isotropic radiated power (EIRP),
however, was estimated to be approximately 1 mW. To operate on 10,000
meters, Raide has a 90 foot vertical antenna using a reconfigured Zepp, fed
via a huge loading coil that is 4 feet tall, more than 1 foot across and
comprised of some 2000 feet of #14 wire. He employs a few thousand feet of
“chicken wire� for his radial system.

The transmission consisted of “XBA� sent at a rate of 120 seconds (2
minutes) per dot and 360 seconds (6 minutes) per dash of CW. In the UK
Nicholson copied the signal on software using a PC sound card with a
preamplifier ahead of it. His antenna is a pair of orthogonal loops, each
20 meters square, at ground level, transformer coupled to the preamplifier.

Read the full ARRL story at
http://www.arrl.org/news/
hams-experimental-vlf-signals-heard-in-the-uk-europe

Spectrogram of the 29.499 kHz VLF signal
http://abelian.org/vlf/sg29499.shtml

Paul Nicholson VLF website
http://abelian.org/

Roger Lapthorn G3XBM Blog
http://g3xbm-qrp.blogspot.com/
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