KondorFPV
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Hello,
I am about to build an array of 4 12-turn helix antennas, spaced 3/4 wavelengths apart, they also have a truncated cone at the bottom to remove or minimize unwanted
side lobes.
Now my uncertainty come when it comes to matching these. I could impedance match each antenna to 50 ohm with a a small matching section (hacker transformer or other methods) and bring them to 50 ohms, but then I'd have to match them together. I could go 2 routes, either rotating the 4 helix antennas to achieve 180° phase shift between 2 elements and then do the same thing for the other 2. That way I could connect 2 in parallel with 50 ohm microstrip section, then use a 1/4 wavelength microstrip on each of the pairs to achieve 100ohm each and then parallel them for 50 ohm.
The other system would be to leave the 4 feedpoints at the same relative position, and use 75ohm microtrip sections 3/4 wavelength on one antenna and 5/4 wavelength on another antenna so 5/4-3/4 = 1/2 which is 180° phase shift, and 100 ohm, and then repeat for the other side , then parallel the 2 pairs.
Now I was wondering what you guys suggest to use, how would I rotate the elements in the first option or if it's best to use the second one.
Let me attach a picture of the 3d model.
One crazy idea that came up is to not match the helix antennas individually (140 ohm each and do everything with the microstrip board).
Please help
Tony.
I am about to build an array of 4 12-turn helix antennas, spaced 3/4 wavelengths apart, they also have a truncated cone at the bottom to remove or minimize unwanted
side lobes.
Now my uncertainty come when it comes to matching these. I could impedance match each antenna to 50 ohm with a a small matching section (hacker transformer or other methods) and bring them to 50 ohms, but then I'd have to match them together. I could go 2 routes, either rotating the 4 helix antennas to achieve 180° phase shift between 2 elements and then do the same thing for the other 2. That way I could connect 2 in parallel with 50 ohm microstrip section, then use a 1/4 wavelength microstrip on each of the pairs to achieve 100ohm each and then parallel them for 50 ohm.
The other system would be to leave the 4 feedpoints at the same relative position, and use 75ohm microtrip sections 3/4 wavelength on one antenna and 5/4 wavelength on another antenna so 5/4-3/4 = 1/2 which is 180° phase shift, and 100 ohm, and then repeat for the other side , then parallel the 2 pairs.
Now I was wondering what you guys suggest to use, how would I rotate the elements in the first option or if it's best to use the second one.
Let me attach a picture of the 3d model.
One crazy idea that came up is to not match the helix antennas individually (140 ohm each and do everything with the microstrip board).
Please help
Tony.
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