TopBand: Vertical antenna phasing

Wed, 16 Jul 1997 14:21:16 +0000

> From:          Steve Narducci <nw9g@netusa1.net>
> Subject:       TopBand: Vertical antenna phasing
> Date:          Wed, 16 Jul 97 04:27:55 +0000

> Been looking at the butternut hf-2v with 160 meter add-on.  This will cost
> a fortune.

And probably not work very well.

> BTW my 160 m wire inverted L , bent at 95 ft with 4 radials is working!!!

Hi Steve,

The key is in two areas. 

One area is keeping the current UNIFORM in the vertical (that 
requires top loading) and loading losses minimal (that requires a hat 
so you can avoid all coils or lossy stubs).

The other area is in the ground system. Four radials are not enough. 
Unless the radials are hundreds of feet in the air, ground losses 
will be severe.

With a phased array, ground losses can become even more of a problem. 
That's because element currents become higher in many phased arrays.

Absolutely the best phasing advice comes from articles like Roy 
Lewallen's stuff in the Antenna Compendium. The stuff you will 
read about using a power divider is non-sense. Phased arrays 
require equal CURRENT (if the elements are equal sized) not equal 
power for maximum F/B ratio. Since element impedances are not equal 
in unidirectional arrays, that means the elements require different 
power....not the same.  Lewallen discusses this in depth, as does 
Forest Gherke? K2BT.

I use a phased array where I feed a 40 meter dipole's vertical 
feedline (about 90-100 ft vertical) as one element, and a 135 ft 
tower as the second element. I get four different patterns and about 
20 -30 dB front to back ratio with this system, so the elements can 
be quite different and still work (although it's easier if they are 
the same).

73, Tom W8JI 

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