With reference to the propagation charts, perhaps one of our Swedish friends
could arrange to borrow the SAQ antenna system from time to time?
John F5VLF
> On 11 Dec 2017, at 11:41, Paul Nicholson <[email protected]> wrote:
>
>
> Jacek wrote:
>
> > could you give a short explanation? i don't really understand
> > nonreciprocal propagation
>
> I don't either, really. The ionospheric reflection
> coefficient depends on the direction of the radio wave relative
> to the Earth's magnetic field. The wave accelerates free
> electrons in the plasma, and they're pulled into circular or
> helical paths by the magnetic field. This alters the phase of
> the reflection and the attenuation of the wave through energy
> loss by collisions.
>
> The consequence is the reflection coefficient isn't a nice
> simple number, it's a 2x2 matrix with each component a
> (frequency dependent) complex number.
>
> It's all the in Appleton-Hartree equations
>
> https://en.wikipedia.org/wiki/Appleton%E2%80%93Hartree_equation
>
> which are quite easy to calculate and program (easier than
> they look at first glance) but few people would admit to
> understanding them.
>
> Spent some time with LWPC measuring the T/A path at some
> different frequencies. The figures below are the extra loss
> on the east-to-west, compared with west-to-east.
>
> The results don't depend much on which end points I choose,
> but are quite frequency dependent:
>
> Midnight UTC:
>
> 18.0 kHz: 2 dB
> 17.4 kHz: 3 dB
> 16.5 kHz: 6 dB
> 16.0 kHz: 9 dB
> 15.0 kHz: 14 dB
> 14.0 kHz: 18 dB
> 13.0 kHz: 16 dB
> 12.0 kHz: 13 dB
> 11.0 kHz: 11 dB
> 10.0 kHz: 10 dB
> 9.0 kHz: 10 dB
> 8.2 kHz: 12 dB
> 5.2 kHz: 27 dB
> 4.2 kHz: 44 dB
> 2.9 kHz: LWPC doesn't run
>
> Generally a lot more anisotropy as the frequency drops,
> but there's a funny peak around 14 kHz.
>
> Midday UTC:
>
> 18.0 kHz: 4 dB
> 17.4 kHz: 4 dB
> 16.0 kHz: 5 dB
> 15.0 kHz: 5 dB
> 14.0 kHz: 6 dB
> 13.0 kHz: 7 dB
> 12.0 kHz: 8 dB
> 11.0 kHz: 9 dB
> 10.0 kHz: 10 dB
> 9.0 kHz: 12 dB
> 8.2 kHz: 14 dB
> 5.2 kHz: 35 dB
> 4.2 kHz: no output from LWPC
>
> The funny peak vanishes during the day.
>
> So, nowhere near as much anisotropy as I thought at
> 17.4 kHz. I don't fancy our chances at the lower
> VLF bands - it might be easier to take the long path!
>
> --
> Paul Nicholson
> --
>
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