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Re: Circular Polarization for WSJT Meteor Scatter

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  • Palle Preben-Hansen, OZ1RH
    Hello, I wrote this text a few days ago on Yahoogroups web interface, but as I have not seen it reflected I try again. Lance wrote: * on 6m, you can clearly
    Message 1 of 10 , Mar 27, 2013

      Hello, I wrote this text a few days ago on Yahoogroups web interface, but as I have not seen it reflected I try again.

       

      Lance wrote:

      >on 6m, you can clearly see the rapid QSB from rotating polarity during the longer burns

      I have a detailed description of MS at http://www.uksmg.org/content/deadband.htm but I did not consider circular polarization. MS is forward reflection which generally preserves polarization. Thus no point in using circular polarization as Joe wrote. The rapid QSB on 6 m MS sound like rotating polarity, but come from high speed wind in the ionosphere blowing the meteor trail into several reflection areas.

       

      The needed azimuth for MS is not great circle bearing as the reflections comes from about areas +-10 degrees from hotspot A and B. Hotspot A and B can be +- 10 degrees or more from great circle bearing and are calculated by WSJT. Thus if your antenna is narrower than about +-10 degrees is might not be optimum and you should in any case understand hotspot A and B so you know where to beam. If you want to call CQ you should have a fairly wide beam in azimuth.

       

      The needed radiation angle in the vertical plane depends on the distance and the elevation is less than 13-15 degrees, see the curve in my text. This is not the elevation angle of your boom but the radiation angle of your antenna, which almost only is a function of antenna height over ground. Radiation angle is described in "Ground gain and radiation angle at VHF" at www.oz1rh.com Pointing your antenna at 90 deg EL for MS is seldom optimum.

       

      Remember that the mentioned degrees represents statistical probabilities of where the reflections might come from, thus an antenna one degree too narrow does not mean no QSO’s.

       

      BTW if you have a good station on 6 m you might consider exploring ionoscatter described in “Ionoscatter on 50 and 144 MHz" at www.oz1rh.com WSJT mode ISCAT is optimized for a combination of MS and ionoscatter on 6 m.

       

      73, Palle, OZ1RH (team OZ5W/OZ9EDR)

      palle at oz1rh.com

       

      --- In wsjtgroup@yahoogroups.com, "Lance Collister, W7GJ" <w7gj@...> wrote:

      > Hi Les,

      >

      > My guess is that you might notice the 3 dB loss from working

      linearly polarized

      > stations.   I don't have any

      current experience running 2m meteor scatter with

      > FSK441, but on 6m, you can clearly see the rapid QSB from rotating

      polarity during

      > the longer burns. I suspect the same thing is true on 2m, and the

      polarity rotates

      > during a meteor scatter contact.

      - rest snipped

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