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Fw: Re: Topband: Phasing Flag antennas?

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Subject: Fw: Re: Topband: Phasing Flag antennas?
From: (Tom Rauch)
Date: Sun, 21 Nov 1999 11:22:56 -0500
Hi Earl,

> 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. =====

Not really. Put one antenna in front of the other, align the 
feedpoints in the same direction, and feed them 180 degrees out of 

That forces a null in the sides, and results in the narrow front lobe I 

> "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.  

It doesn't matter if each cell has a null off the back, except that 
prevents having response off the back if the null is very deep in 
each cell.
I do this all the time in commercial antennas, or my own antennas, 
it not only models just fine, it also works quite well in practice.

>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!! =====

Agreed. But you can certainly move an addition pair of nulls around 
the antenna in any direction. That's basic to how the MFJ Noise 
Canceller I designed works on groundwave noise.
> 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.  

It makes no difference if a feedline is involved, except the feedline 
reduces bandwidth stability of the null and can change the 
requirements of equal voltage or equal current at the phasor 

I phase two antennas through 2500 feet of cable, and also have 
hase delays integrated right in some antenna cells.

This is old, time-proven concept right at the core of all directional 
array design. Unless the broadside area is wide enough to force a 
deep null in an area of major radiation, you are better off using end-
fire directivity and forcing a null in a side lobe that way.

This is a very well known effect.

73, Tom W8JI

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