LF: W4DEX at 8540 Hz in Todmorden

[Paul Nicholson <vlf0403@abelian.org>]

Dex surprised me last night with a carrier on 8540 Hz,
GPS-locked and the ERP would be circa 100uW.

Tx was stable from 21:25, detectable in the UK by 22:30,
and a good overnight signal until 03:00 when Dex planned to
switch off.

 http://abelian.org/vlf/tmp/171202a.gif

Signal about 0.1fT and 30nV/m, about 30 electrons worth of
charge on the new E-field antenna.  Anything with double
figures is a good amateur signal!

 H-field: -27.7 dB in 1Hz, phase -109.4 deg;
 E-field: -26.0 dB in 1Hz, phase -108.1 deg;

It's not unusual for the new E-field rx to do better than the
loop rx.   Looks like I need to hurry up with the upgrade to
the H rx!   I've cleared bench space for the replacement and
parts are on order.

I measured the bearing using three different methods:

 Watson-Watt goniometry: 273.1 deg

 Poynting vector: 287.5 deg

 Tsuruda/Hayashi NPE:  282.3 deg

The great circle bearing is actually 284.6 deg.

NPE should be the most accurate method - no polarisation error
but relies on precise relative phase measurements between the
three channels.

--
Paul Nicholson
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