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Fw: Re: Topband: Phasing Flag antennas?

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Subject: Fw: Re: Topband: Phasing Flag antennas?
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Date: Sat, 20 Nov 1999 20:57:59 -0800
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From: Earl W Cunningham <>
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Tom, W8JI wrote:

"Earl, I don't know how you modeled the antenna...but you must have
missed something."
Don't know what I missed, Tom.  Phasing two elements is pretty

"With only 100 foot end-fire spacing the antenna will have much more
directivity and/or better F/B than the broadside pair on 160."
End-fire spacing improves the array in its vertical radiation pattern,
but hardly at all in its horizontal pattern.  This is how the model shows
it, Tom.

"He also could steer the nulls all around the antenna."
I'd agree with you if the individual antennas in the array were
nondirectional like verticals, but remember that here we're dealing with
an array of antennas that are already unidirectional by themselves as a
single antenna.  The individual parts of the array already have a F/B of
> 40 dB.  It's impossible to null the front of an array of non-rotatable
Flags or Pennants and bring up the rear!!
"End-fire is ALWAYS the way to go unless the array is very large.  That's
why small yagi's have more directivity than collinear antennas, and why
the 8JK arrays work so well. That's why commercial systems use end-fire,
unless the spacing approaches 1/2 to 5/8 wavelength.  Even so, the SAME
spatial distance (5/8 wl) will produce a sharper array when filled with
end-fire cells."
It appears that we're comparing apples with oranges here.  If the
"elements" in the array are Flags or Pennants, then I agree with your
statement in the last sentence in any case.  In fact, a four-element
endfire/broadside array of Flags or Pennants has a pattern superior to a
2-wavelength Beverage!


Using 180 degree shift between the from element to back, I modelled two
Flags with about the HPBW you sited.  HPBW is about 50% more narrow than
the case you sited for 150  foot broadside spacing on 160 with those
I don't know why our models disagree so much.  Let me know if you use
EZNEC.  If so, I'll send you my model files for 1, 2, and 4-el Pennants. 
If you'd like to, you can send your model files as an attachment to me
at: (Juno doesn't provide for attachments).

"The use of a 1025/1026 would allow him to rotate the nulls in ANY
direction with the end-fire arrangement, and the array could be made to
have maximum radiation in directions other than the front.  As a matter
of fact some phase shifts will make it fire nearly off the back!!"
I'll have to see it before I can believe it, hi.  With two Pennants
spaced 90 degrees in the endfire configuration, I tried both 45 and
180-degree phasing (as well as normal 90-degree phasing).  None of them
rotated the lobe an iota (although the shape of the lobe changed).  I
tried lagging the rear element by 90-degrees and that only tried to null
the front of the lobe, leaving what's left off to the sides.

Maybe our disagreement lies in which end of the feedline you put the
phasing device.  I'm changing the phasing in my models right at the
feedpoints of each element, with no feedline involved.  Maybe it's a
whole new ball game if the phasing device is at the receiver end of the
feedlines.  Even so, I don't see how you can reverse or significantly
change the directivity of an array where each individual element in the
array is already unidirectional -- and the models prove it.

73, de Earl, K6SE

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