[time-nuts] Quadrifilar Helix Antenna

Jim Lux jimlux at earthlink.net
Sun Jun 10 00:39:46 UTC 2012


On 6/9/12 5:03 PM, David Kirkby wrote:
> On 10 June 2012 00:14, Azelio Boriani<azelio.boriani at screen.it>  wrote:
>> Yes, you are right and this is the problem I have. I'm aware that wonderful
>> things can be done starting with a simulator, not just tell whether or not
>> the antenna will be on frequency. I have to fill the gap and learn how to
>> successfully use a simulator.
>
> The other issue of course is the cost of them. Prices can easily reach
> 5 figures - $, Euros or GBP.
>

NEC can do a pretty good job on a helix, and it's free. I like 4nec2 as 
a front end.

NEC will also do a patch: Model it as a grid of wires using the 
guideline of "surface area of wire is spacing between wires".. that is, 
if you have wires on a 1cm grid, then the wire diameter should be 1/pi 
cm.  Even if you thin the wires out (so you can get them closer to the 
ground plane), it still works pretty well.  While in days of yore, 
running a NEC model with 10,000 segments would have been an overnight 
run, today, it's pretty quick.



But yes, if you want to design the feed for a patch, or do RF circuit 
layout (particularly in an enclosure), you want HFSS, ADS, or programs 
of that ilk.  ANd, they are, as noted, pretty pricey. Worth every penny 
if your job is doing this kind of design, but kind of a big step for a 
casual experimenter.








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