[Antennaware] Too good to be true

Davor Virkes davor.virkes at ht.hr
Wed Apr 7 10:21:15 EDT 2004

As you most probably know, NEC-4 engine is not circulated outside NATO, and 
many of the "erudites" are stuck with NEC-2. That poses an interesting 
problem regarding antennas with buried wires, or wires that touch ground. 
This antenna is touching ground, and NEC-2 is not happy about it.
I often find it annoying to see these unrealistic gains, but bear in mind 
that the gain is referenced to isotropic antenna, which gives you 2dB gain 
for anything that resembles a dipole, and in case of Earth as a reflector, 
you get additional 3dB for radiating only in one half of space. Loops may 
be observed as stacked dipoles, hence 3 dB more. And here you are, a hefty 
8dB gain. But where? Into the stars above.
I like my NEC antennas in free space. If some ground is required, I make a 
wire grid beneath, and calculate in free space. Only when I'm 100% positive 
about gain AND distribution of currents, I check it against a "real" ground.
Have fun

At 23:07 2004.04.06 -0400, you wrote:

>I have inserted a NEC file of a antenna that has me puzzled as to why
>the gain it gets. Seems quite too good to be true. Will send a .EZ
>file to anyone who requests it.
>Would appreciate it if the erudite could point out what is going on.
>Running EZNEC/4 with NEC-4 engine.
>Thanks, Guy.

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