Re: VLF: W4DEX trans-Atlantic at 8971 Hz

[DK7FC <73dk7fc@googlemail.com>]

Hello Dex and Paul,

My compliments to this great success below 9 kHz. Finally someone made 
it :-)
This should rise some hope to do it the other way if the same 
professional RX setup is available in the US.
73, Stefan/DK7FC

Am 02.06.2014 21:44, schrieb Paul Nicholson:
> 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.
>
>  http://abelian.org/vlf/tmp/w4dex_140602a.gif
>
> 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
> bandwidth.
>
> 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.
>
> --
> Paul Nicholson
> --