[hpsdr] Scientific publication using HPSDR published

[Scott Traurig]

Ah, I see what you are saying, Ben. By using a polarization diverse
antenna, one can then suppress the dominant cause of fading, which is cross
polarized multipath, leaving primarily only the spatial multipath as the
source of remaining fading.

Thanks,

Scott

On Sun, Jun 16, 2019 at 12:35 PM pa5bw <pa5bw at xs4all.nl> wrote:

>
> Hi Scott,
>
> You correctly state that the ionosphere plus the earth's magnetic field
> split any wave enterig the ionsphere in a left-hand and a right-hand
> circularly polarized component.
>
> The advantage of a circularly pola about, but the fading reduction,
> especially in NVIS propagation.
> There most of the fading is caused by interference of the left-hand and
> right-hand circularly polarized waves, with minima of -35 dB. They will
> virually disappear when using circular polarization.
>
> You can find several scientific publication on this subject on my
> ResearchGate website (Ben Witvliet).
>
> 73, Ben PE5B
>
>
> Date: Fri, 14 Jun 2019 16:29:11 -0400
> From: Scott Traurig <scott.traurig at gmail.com>
>
> It's probably worth mentioning that if you build an HF turnstile antenna
> (two crossed dipoles or inverted V's) there are no modifications required
> to PowerSDR or Thetis to use them as a circularly polarized array on
> receive. Just feed each dipole to RX1 (ADC0) and RX2 (ADC1) with equal
> length coaxial cable of the same type. Then use the "Diversity" function to
> invoke a positive or negative 90 degree phase difference with unity gain.
> You'll get either left or right hand circular polarization. I've always
> wanted to try this, but I do not have a way to put up the required
> antennas.
>
> Of course you'll have to choose one antenna or the other for transmit. Or
> you could build a 90 degree phasing harness and do it the old school way
> but the phasing harness will only be correct at a single frequency.
>
> This applies to more than just NVIS. All signals reflected off of the
> ionosphere become circularly polarized. If you can match your polarization
> you can avoid the polarization loss from circular to linear. However at
> worst that is only 3dB in theory.
>
> 73,
>
> Scott
>
> On Fri, Jun 14, 2019 at 7:36 AM Erik van Maanen <pa3des at xs4all.nl> wrote:
>
> > Our scientific publication on NVIS research is just published in MDPI
> > Sensors journal.
> > We used a measurement system based on the ANAN200D and powersdr as well
> > as a large amount of self developed hard and software.
> > We specially like to thank Joe K5SO and Doug W5WC for their support and
> > modifications of powersdr.
> > (These modifications are now part of the normal powersdr release.)
> >
> > The publication is Open Source, freely downloadable for anyone, and can
> > be found on:
> > https://www.mdpi.com/1424-8220/19/11/2616
> > Besides good reading material for the weekend we also hope it can be
> > used as another example of the value of ham radio.
> >
> > 73' Erik PA3DES and Ben PA5B
> >
> >
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