Topband: Polarization on 160m

Yuri Blanarovich k3bu at
Wed Nov 28 11:31:39 EST 2018

Not knowing about "gyros", but when operating and having vertical and 
horizontal antennas available, I remember times when QSB was happening 
on one antenna, switching to the "other" polarization antenna would 
bring the signals up.
My conclusion was that at the times the signal's polarization was 
rolling around, especially when far DX.

 On Wed, Nov 28, 2018 at 09:22 AM, Robert Parkes via Topband wrote:
> Polarization on 160m
> Interesting discussion and one I suspect we wish could fully 
> comprehend !
> When the wave front meets the ionosphere and the wave splits the 
> critical frequency is different for the two waves, commonly known as 
> foc and fxc. 
> This difference (from memory) is half the gyrofrequency and can often 
> be seen on Ionosonde plots with two sets of reflections. The gyro 
> frequency depends on the strength of the magnetic field at that point 
> of the ionosphere so can vary from 700kHz to 1.4MHz where the radiated 
> wave interacts with the Ionosphere Layer be it, E layer or F layer.
> Being radio amateurs and pushing the envelope we are trying to make 
> that illusive QSO so we need to excite a propagation path which is 
> normally at the limit in order to chase the DX.
> Assuming conditions are favourable, and if the angle of arrival and 
> critical frequency is such that it favours both wave fronts then for a 
> single and multi-hop transmission both the O-wave and the X-wave will 
> be propagated.
> The higher frequency of the two wave fronts, the X-wave may propagate 
> which could result in a QSO whilst those around us may not have quite 
> the same favourable conditions and only the O-wave is propagated  on a 
> differeing path while the X-Wavecould fall by the wayside and not be 
> propagated. 
> One result of all this variability could result in what has been 
> called spotlight or torchlight propagation.  I recall Eric K3NA giving 
> a talk along these lines when referring to 3B7C 160m operations and 
> how that spotlight moved across North America during the course of his 
> opening to the US.
> There is a possibility that Circular Polarisation would assist 
> with both the O and X wave modes of propagation and it could be argued 
> that a "compromise" Inv-L antenna provides this with its Vertical and 
> Horizontal elements making up the antenna and resulting mixed 
> polarisation.After all a number of amateurs have had good success with 
> an Inv-L.  
> 73sBob ParkesG3REP(ex - S21YP, 4S7RPG, A45XF, VS5RP, P29PR)
> _________________
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