[hpsdr] Scientific publication using HPSDR published

[Scott Traurig]

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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