[TowerTalk] Stacking Log Periodics-Certical Patterns

[K7GCO@aol.com]

!n a message dated 12/7/00 4:04:29 AM Pacific Standard Time, 
 prforbes@tbsa.com.au writes:
  K7GCO writes:  
  >   Cheers,    Steve    K7LXC >>  This is very true but there is another 
  >variable.  IF THE HORIZONTAL PATTERN IS WIDER, SO IS THE VERTICAL
   PATTERN  and 
  >this fills the higher angles with far more RF than the loss of gain and at 
  >certain times of the day do a bang up job on DX also.  This is comparable 
    to a 2 element quad at say 1/2 wave or slightly higher do so well.  It's 
the 
  >lack of gain that makes it work closer to the ground.  High gain beams 
    don't work well close to the ground.  K7GCO 
  >
  Is it NECESSARILY SO that a wide horizontal pattern means a wide vertical
  pattern as well?
  
  The vertical pattern for a horizontal log periodic array is a function of
  several things:
  
  (1) ground reflection effects
  (2) ground impedance effects (when within one wavelength height above 
ground)
  (3) the spacing of the elements within the log cell which are active at that
  frequency (in other words the Design parameter of the array (tau) and the
  relative element spacing constant (sigma)).
  
  In all my literature searches on the log periodic (both amateur and
  professional) there is little discussion of the effect on the vertical
  pattern when near the ground, with most computer modeling being free space
  situations.
  Cheers
  Peter   VK3QI  ( an 18-29 mhz log periodic user)
       S IT NECESSARILY SO THAT A WIDE HORIZONTAL PATTERN  
  
  >                          "Now you have the rest of the story."  
 
 Peter: Are you sure you don't want to reconsider what you said?
 
 Does lack of literature you could find mean that LP's are immure to and 
there 
 isn't any affect on the vertical pattern when close to the ground for LP's?  
 When only a few elements are working like in a Skip Log, there is no way a 
 sharp vertical pattern can be created.  It like gain is related to the 
length 
 of the boom.  It's vertical pattern will compare to any other beam of 
similar 
 gain.  It will be on the board side if the horizontal pattern is on the 
broad 
 side.  If you have examined the free space vertical patterns of beams in 
 soft ware as you infer, you should have noticed that the free space vertical 
 pattern is also always at least 20-25% broader than the horizontal pattern 
 when tuned for F/B.  It's a littler sharper if tuned for max gain.  Spend 
 some time in Eznec.   
 
 The ground reflections from a LP are subjected to exactly the same slavery 
to 
 ground reflections as from any other antenna.  Reflection Factors show or 
 predict at what angles the lobe are in for various heights.  I strongly 
 suggest you do another literature search and learn about these concepts.  
Try 
 the ARRL Antenna Manuals of the 50's.  If you can actually use antenna soft 
 ware, put a 2 element quad in it, look at the free space patterns and then 
 ground relections for different heights starting at 1/2 wave.  Then do it 
for 
 a Skip Log.  You will see that for a LP of similar vertical pattern 
 sharpness, the ground will treat it the same as a quad.  The ground is an 
 EQUAL OPPORTUNITY REFLECTOR FACTOR for the same height and it doesn't 
 discriminate like certain Florida vote counters. 
 
 I covered #1 above.  Show me data that supports what you say in #2--make 
your 
 point with something revolvant.  I think in #3 you are trying to say all 
this 
 controls the free space gain.  So what's your point?  Both patterns are 
 related to the gain and the vertical pattern is always broader than the 
 horizontal unless the beams are stacked vertically.  That's exactly why I 
 wanted to stack 2 LP's in the normal V manner and also with the booms 
 horizontal.  I would then not have them close to the ground, however.  Do 
you 
 know why?
 
 You seen to have a flare for the dramatics.  First off you didn't show what 
 Steve said (A) and should have been included for clarity so readers could 
 see what my comment was all about.  I included it below.  His statement was 
 correct, I just added to it in another plane that is seldom talked 
 about--the vertical pattern--the one you can't see when the beam is rotated.
 
 For some reason you saw fit to print 2 statements in CAPITAL LETTERS.  Why 
 did you do that?  What useful purpose did it serve?  What useful purpose did 
 the whole post serve?  K7GCO
 
  
  (A)    FYI the mult station (or second station) at W6GO is an LP. He says 
 that 
   the reason he likes it is because it's got a bigger forward pattern than a 
   monobander or even a tribander which is useful in contesting where a real 
   sharp antenna can be a disadvantage.
   
   Cheers,    Steve    K7LXC >>  This is very true but there is another 
  variable.  If the horizontal pattern is wider, so is the vertical pattern 
 and 
  this fills the higher angles with far more RF than the loss of gain and at 
   certain times of the day do a bang up job on DX also.  This is comparable 
 to 
  a 2 element quad at say 1/2 wave or slightly higher do so well.  It's the 
  lack of gain that makes it work closer to the ground.  High gain beams 
don't 
  work well close to the ground.  k7gco 
  
                            "Now you have the rest of the story."  
  
 
 

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