I started trying to build my own Yagi. So i ran into maybe some very well known Websites that show how to do it – however, i wanted to try with some theory first, before actually attempting to build one.
I've downloaded a program called "VK50J's Yagi Calculator" (by John Drew) – this designs the Yagi (after some input) with a whole construction guide. But when i input those values into another Software "YagiModel" (a small Java applet), the values differed. And when i tinkered around with the values, they even increased above those, that the Yagi Calculator output (the dBi gain).
So, i wrote a little Program, that would bruteforce the values through that Java applet and generate me a list with all the dBi gains and different lengths and positions of Reflector, Driven element and 1 director.
Using the following Input for the Yagi Calculator:
- Frequency in MHz: 2442 (skipping channel 14)
- Number of directors: 1 (to keep it simple)
- Diameter of element (mm): 2
- The Elements are all round and there is no metal boom
The other settings seemed to have no influence on the outcome: the antenna would always have a gain of 6.9dBi with the following construction plan:
- REFLECTOR 59,3 mm long at boom position = 30 mm (IT = 22,0 mm)
- RADIATOR Single dipole 56,6 mm tip to tip, spaced 25 mm from reflector at boom posn 55 mm (IT = 21,0 mm) OR Folded dipole 57,7 mm tip to tip, spaced 25 mm from reflector at boom posn 55 mm (IT = 21,5 mm)
- DIRECTORS Length: 50,8mm Boom position: 63,8mm
(The construction plan was shortened)
When i input that in the YagiModel-Applet, i get similar results – BUT:
with the values that i've bruteforced, the antenna gain jumps up to 9.91dBi
List of Elements:
- Length: 61.0mm, Position 0mm
- Length: 66.0mm, Position 10.0mm
- Length: 53.0mm, Position 45.0mm
Element diameter was always 2mm, the frequency always 2442MHz. Unit: Millimeters, and as for the YagiModel-Applet, i used "Conductivity->Perfect" (even with worse conductivity, the difference was still very significant)
Now my question is: Which values should i trust? Could the bruteforced ones really be better than those that the Yagi Calculator outputs? Do i just face this difference, because there is only 1 director – meaning, the difference would rather approach zero, the more elements i would add?
I know bruteforcing is not a very elegant way to calculate anything – but in my case i simply lack of ALL the formulas to actually do the calculations, so this was just a quick-and-dirty aproach to get started.
I'm in no way an expert about radio signals, or electronics, i just simply love it, even though it doesnt love me back. So i'm sorry if this question is maybe kind of "stupid" or solveable on my own if i just had read more about the topic first. I would have built this, but unfortunately i also lack of any equippment to really meassure these theoretical results…
Thank you for reading through this and thanks ahead for any answer or hint on this 🙂