I'm trying to null out vertical signals from a particular suburb which is about 40 kms away from my location by pointing a 4 element 10 m yagi such that the direction i want to null out is off to the side at about 90 deg to the direction of maximum gain.

The polarization of signals from the direction of the yagi's maximum gain isn't important because i'm interested in long distance via skip and then the polarization is always changing.

Will the yagi provide the best side rejection for the vertical signals coming from the offending suburb if I mount it vertically or horizontally ?

Keeping in mind that in theory a yagi has little or no gain in the plane it isn't positioned in.

To re-phrase, what provides more side rejection to vertically polarized received signals :

a. The cross polarization attenuation provided by a horizontal yagi coupled with the minimal gain in the vertical plane and the associated minimal nulls in the vertical plane it has which can be used to null out vertical signals from some directions.

b. The fact that a vertical yagi has gain in the vertical plane and so then has definite nulls in the pattern which can be used to null out vertical signals from some directions.

When using a 4-element Yagi antenna, is there any other way I can best reject signals coming from a particular direction ?

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    $\begingroup$ You've said the signals you do NOT want to receive have vertical polarization — what is the polarization of the signal(s) you DO want to receive? $\endgroup$ – natevw - AF7TB Jan 14 '19 at 18:43
  • $\begingroup$ Are you trying to null out some local interference? $\endgroup$ – Mike Waters Jan 14 '19 at 21:57
  • $\begingroup$ Ah! Will this Yagi be pointed towards that? (Also, if you reply using the format @mikewaters, then the person will be immediately notified. Just type an @ symbol followed by the first character or two of the person's user name, it will auto-complete; just click on the little pop-up.) $\endgroup$ – Mike Waters Jan 14 '19 at 23:31
  • $\begingroup$ @mikewaters no, i imagine i would point the yagi so that the area i want to null out is off to the side $\endgroup$ – Andrew Jan 14 '19 at 23:43
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    $\begingroup$ @mike Thanks for the replies - but i'm not convinced yet. I now have a 4 element horizontal 10 m yagi pointing north and a 3 element vertical 10 m yagi pointing in the same direction. When both antennas are compared when receiving the same stations, vertical stations roughly west of both antennas in general are 2 s points stronger on the 4 element horizontal yagi. $\endgroup$ – Andrew Feb 27 '19 at 2:40

It should be mounted horizontally. The deepest nulls would be ~90° off the sides.

  • $\begingroup$ To be absolutely certain, I would have to model it in a manner that shows the polarization in the plot. $\endgroup$ – Mike Waters Jan 14 '19 at 23:54

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