Topband: Elnec model of Inv L

[Tom Rauch]

> I entered a 3/8wave Inv L with a 1/4 wave counterpoise at 5' off ground
> and noticed fairly low gain of .492dbi at maximum takeoff angle.  Then by
> accident I eliminated the counterpoise as I was about to add 60 radials
> but executed the model before I added them and noticed the reported gain
> rose to 2.1 dbi with no counterpoise and no radials.  With the 60 radials
> of course the gain rose to 2.538 dbi.
> 
> Why is there more gain with no counterpoise?

Besides what John posted, there is another effect that we should 
keep in mind when modeling.

Eznec "looks at" the antenna from an extremely large distance 
away. Looking at the antenna pattern from a distance large 
compared to ionospheric height can give the misleading picture of 
showing less useful low  radiation than really exists.

My 300 ft high dipoles model to show much better FS than my 
verticals at almost any wave angle, yet the exact opposite appears 
to be true. The dipoles only win a very small percentage of the 
time, and almost never beat my verticals distances over a few 
hundred miles except at sunrise or under disturbed conditions.


73, Tom W8JI
w8ji@contesting.com



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