[TowerTalk] KC1XX 8 10M yagis & N4KG's comment

[Dale Jones K5MM]

  Ladies & Gents:
  Tom's (N4KG) comments are 'right on', and their is one additional
  point of consideration with regard to fading -- QSB -- of an incoming
  signal.  That is the polarization of the incoming signal.
  
  Many years ago, and no doubt more recently too by others,  the late K6CT
  did much experimenting from the Los Angeles area on 10 meters with
  horizontal, vertical, and cross-polarized yagi antennas.  His 
  conclusions were published in an Amateur Radio article - CQ I think - 
  sometime during the 1960's.

  The general conclusion was that polarization seems to continue to rotate
  and the cross polarized (two driven elements fed simultaneously, and 
  positioned 90 degrees apart) antenna was far superior to either of the
  other two during weak signal times.  It is recognized that a 3 db loss
  occurs when feeding two driven elements simultaneously.  

  I recall talking with OM K6CT in the late 1960's about this, and he 
  explained that using identical receivers, feedlines, etc, on two 
  separate antennas while listening to the same station, the cross-polarized
  yagi was consistently better at band opening and closing times, and during
  general weak signal times.  When signals were very strong the difference
  was not so noticeable.

  VHF folks have drawn a similar conslusion, since they use that type of 
  yagi on their satellite operations.

  So, it does seem that there is more to weak signal receiving of an rf
  signal than just lots of horizontally polarized gain, one horizontally
  polarized antenna at any one given height.

  73
  Dale Jones,  K5MM
****************************************************************************

 On Fri, 19 Sep 1997 07:09:38 -0400 (EDT)   K4OJ@aol.com   writes:

 I am sure the major consideration in the development of this antenna 
 system was not the resulting gain, but the resulting consistancy on 
 receive of incoming signals as prop changed.....fading should be way 
 way down....

          there is "always" an antenna at the right height!  

.......................................

 I don't believe it works that way, at least not if they are all phased 
 in at once.  With all 8 antennas fed in phase, you will get one big 
 lobe at a low angle, (and possibly some well suppressed minor lobes at 
 higher angles).

 To see high angle signals, the bottom antenna would need to be switched
 in by itself.

 de  Tom  N4KG
**************************************************************************** 


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