[TowerTalk] Antenna model

[jimlux]

On 2/22/17 5:16 PM, john nistico wrote:
>
> I used eznec to model a small beam for my son who is going for his
> general. 2 element 20 meter yagi on a 10 ft boom the results were
> pretty good. Any suggestions on how to improve? The driven element is
> 16fy 6 inches per side reflector is +10%
>

It's a two element design, so it's probably not real sensitive to
misalignment or length errors.  But that's one of the real values of
modeling.. you can change the angles (so that the elements aren't
perfectly aligned, like when the clamp slips) and see if the match or
gain change significantly.  Ditto if you are off by an inch in length.

What sort of feed are you using to get 50ohms? uniform diameter tubing 
for the 10 foot
pieces sticking out each side? what diameter?


Running the optimizer in 4nec2 on the example 2 element yagi, with 10 
foot spacing, I get driven element of 16.188 ft (16 ft 2-1/4") and 
reflector of 16.805 ft (16 ft 9-2/3"), with forward gain of 12.2 dBi and 
1.8:1 VSWR  (because the Yagi has a 27 ohm feed point impedance.. any 
sort of matching network will fix that nicely)

Your design seems to tune a bit lower in frequency..it has about 11 dBi 
gain across the band.  But it also has a 1.4:1 match to a 50 ohm line at 
14.1.