Wednesday, 4 June 2014

W4DEX Crosses the Atlantic on 8.9KHz

W4DEX, Dexter McIntyre, has succeeded in getting his 8.9KHz signal from North Carolina to Europe. It was detected by Paul Nicholson in Todmorden, England. Paul's announcement on the RSGB's LF reflector heralded the breakthrough achievement.

At 2014-06-01 10:00 UT W4DEX began a long transmission of GPS
locked carrier at 8971.000 Hz from 35.273N,80.371W.

Between 2014-06-02 00:00 and 06:00 a carrier was measured
at that frequency here in Todmorden 53.703N,2.072W with flux
density around 0.05fT. It was not very significant so I
combined the H-field and E-field receiver outputs (correcting
for their known phase and amplitude response) to produce a
uni-directional antenna response. This brought the signal up to
a significant level.

The signal bearing was roughly west. W4DEX is bearing 285 deg
from here. The S/N is max on a bearing of 315 degrees which
puts the prevailing south-westerly background nearer to the
side of the antenna response.

This gave the signal a respectable 12.5dB S/N in 46uHz bandwidth.


W4DEX Carrier Received in England

This was the strongest peak in a span of over 6500 Fourier
bins so is quite significant.

The carrier was also visible during the daylight path in 23uHz
bandwidth with average strength of around 0.02fT and with
similar S/N thanks to the lower day time noise and reduced

At 2014-06-02 12:00 Dex altered the TX frequency for a blind
confirmation test. Six hours later the carrier (in 46uHz)
had vanished and a new signal appeared at 8971.100 Hz with
the same strength.

An email response from Dex confirms 8971.1 as the new frequency.

Range W4DEX to Todmorden UK is 6194 km.

Ratio of day/night flux density agrees well with LWPC
predictions for this path. LWPC predicts strongest night
signal between 00:30 and 04:30 and a sliding spectrum window
agrees with this.

LWPC requires ERP of 150uW to reproduce the observed flux
density. This is in the center of the ERP range estimated
from W4DEX antenna dimensions and measured antenna current.

I was able to copy Dex's 74KHz QRSS signals in January but going ten times lower is difficult to imagine.

It seems the region below 9KHz is licence-free open-territory for experimenters in the U.S.
This achievement is even more impressive when one considers the low erp and the 'backyard' antenna system used by W4DEX.

Update: Dex has now posted a  LINK to a description of his transmitting setup.


Anonymous said...

Incredible one

Jan Lustrup LA3EQ said...

Well done!
73's LA3EQ Jan