[TowerTalk] modeling compare: 80M, 2EL vs 4SQ

[David Gilbert]

There is a lot wrong in that post.

1.  HFTA doesn't model vertically polarized antennas, so if the 
conclusion is to go with a 4-square you aren't going to learn a thing

2.  Radials, no matter how extensive, will not do a thing to affect the 
vertical radiation pattern of a vertically polarized antenna. The 
conductivity of the land beyond any practical radial field rules the day 
... and night.  Radials affect efficiency, not pattern.

3.  Elevated radials make sense versus using an extensive ground screen 
over really poor ground, but again ... that only affects efficiency and 
not pattern, and doing both makes little sense.  The elevated radials 
mostly shield the ground screen from providing any useful benefit unless 
the ground screen is a lot larger than the area of the elevated radials.

Dave   AB7E



On 3/16/2015 5:32 AM, Ed Sawyer wrote:
> Its an interesting thread.  A few comments.
>
>   
>
> -          Its all about gain.  You don't care about F/B because if you can
> consider these antennas, you are going to have beverages.  And if you have
> good beverages, you will essentially never listen on your TX antenna again -
> except for certain specific circumstances.
>
> -          If you have negatively sloping terrain of ANY kind towards EU,
> you need to HFTA model it.  Not NEC antenna model it.  You do NOT have to
> have the specific data.  You can create your own ray data to see what the
> effect will be.  You do NOT have to have the specific info to understand the
> effect of that slope.  Estimate it, and you will see the effect.
>
> -          80M yagis are notoriously difficult to maintain, so personally,
> with negative slope to EU, if budget and space are no object, I would do an
> elevated 4 square - of 4 - 85 ft towers with the insulated adapter at the 20
> foot level.  Do 4 radials under each one and then lay out a full ground
> screen (ala K3LR style) in the full square area of concern (essentially
> under all area that has a radial on it).  That way you really don't care
> what your ground conductivity is.
>
>   
>
> Ed  N1UR
>
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