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To: <[email protected]>
Subject: RE: LF: NA VLF
From: <[email protected]>
Date: Tue, 9 May 2017 13:55:05 -0400
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Thanks for very good AoA validation of Joe's signal.

Not sure if Joe's antenna is pure vertical and remain intrigued by VLF AoA 
error with VLF TX antennas that have non-vertical E components due to (a) 
non-vertical slope of TX antenna or (b) infrastructure near TX antenna (or RX 

I noticed that you used phase with Watson-Watt, and wondered if you used phase 
as in attached .png file [which presumes crossed loops and a second antenna 
(omni) for blanking to implement unambiguous Watson-Watt solution]; or if you 
used phase as part of the time dependent complex amplitude signal of a center 
antenna for a four-element (e.g. Adcock) array.  [asking because I'm very 
unfamiliar with Watson-Watt particulars and have not seen a Watson-Watt 
reference to a phase term used with a single (2-element) crossed loop except in 
the above/attached context which presumes an omni (2nd antenna, in addition to 
crossed loops) for blanking]

The following describes in agonizingly long form why the above question (how 
phase is used in your Watson-Watt calculation of the bearing of Joe's signal) 
is related to my interest in Stefan's experiments at 970 Hz and 2970 Hz:
In recent spare time I measured VLF phase from distant sources with a rotating 
single-axis air-core VLF loop in various proximities to various familiar 
infrastructure elements including large/small metal items, vehicles, water, 
buried utility conductors, and buildings (interior and exterior), and phase 
effects of loop rotation have been small except with unusually close proximity, 
and still well-behaved albeit larger phase variation with loop rotation in 
unusually close proximity to large/long conductors (for example, vehicles or 
very long conductors). These results are (directly or indirectly) not 
consistent with reports of large AoA errors with (in some cases) 
amplitude-based and (in other cases) phase-sensitive VLF AoA measurements 
(including Tkalcevic "...1400 km distant" and Horner "Accuracy of Location of 
Sources..."). Tkalcevic makes an interesting case for AoA error given 
horizontal components from the VLF TX, and some AoA elevation-angle sensitivity 
at the RX is indirectly implied in Tkalcevic and corroborated in a different 
context in Horner; but some other examples which include sensitivity of phase 
to small changes in loop orientation or loop position leave me wondering about 
the RX antenna cables etc. in those high-sensitivity cases, because I haven't 
observed much phase sensitivity to small changes in position or orientation of 
a single-axis air-core loop.

Much of my interest in the phase aspect of your Watson-Watt AoA measurement of 
Joe's signal is related to Stefan's 970 Hz and 2970 Hz experiments, wherein the 
high elevation angles of experiments at sub-wavelength distances, and a modal 
particularity at 2970 Hz,  may exacerbate the effects (on AoA and 
near-threshold amplitude) of any horizontal components from the TX antenna. So, 
given the good AoA result with your phase-included Watson-Watt calculation of 
the bearing of Joe's signal, any basic description (a few words) on how you 
used phase would be helpful and appreciated, as it might enlighten potential 
phase considerations in Stefan's 970 Hz and 2970 experiments (and AoA in the 
6.95 KHz and 8.27 kHz experiments).      



-----Original Message-----
From: [email protected] 
[mailto:[email protected]] On Behalf Of Paul Nicholson
Sent: Monday, May 8, 2017 11:46 AM
To: [email protected]
Subject: Re: LF: NA VLF

Watson-Watt calculation from the antenna amplitudes and phases of the overnight 
signal gives 244 degrees which is reasonable given the background noise from 
the south west (pulling the apparent bearing southwards from the great circle 
280 deg).

Without any calculation, I can see from the relative antenna phases that the 
signal is from the west: the E/W H-field is very obviously inverted (relative 
to the E-field) from its familiar polarity on European signals.

Joe wrote:

 > The carrier was generated with an undisciplined 10 MHz DOCXO  > clocking an 
 > ad9851. As Markus points out, the maths puts it  > high by 92.5 uHz.

Overnight signal peaks at 8270.0070625 Hz +/- 0.5 uHz.
Therefore about 3.6 ppb low of the DDS nominal frequency of 8270.0070925...

If I align the FT bins with that frequency, the overnight signal becomes a 
sharp line -

with a respectable S/N of 13.9 dB in 46.296 uHz.

I'm now confident that this little peak in the spectrum is 10uW from VO1NA.  
Distance is 3545 km.

The signal amounts to about 2.6 electrons on the E-field probe.
How's that for a signal report Joe?

Also getting a bit of a signal visible at Forest, Virginia.
Not a very significant peak but it has the same offset.
Only visible on the overnight signal, nothing yet on the daytime.  Distance to 
Forest is 2442 km so that's very good for a land path.

Forest is E-field only so no rejection of the South American nighttime sferics.

Paul Nicholson

Attachment: Watson-Watt DF Solution with Correction for ''DF-Solution-Ellipticity g....png
Description: PNG image

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