Posted 05 January 2011 - 01:28 PM
I am working on a few circularly polarized antenna designs: the cloverleaf antenna and a reflected turnstile antenna. For the turnstile I think I need to mount the reflector .2-.25 wavelengths away from the center of the antenna for what I hope is about 5 dbi gain. Unfortunately I can't seem to model it to verify this.
I am also trying to develop 2 new antenna designs, the bluppnik and the Caltrop. Both require a 90 degree stub. I hope to achieve omni directional circular polarization with these antennas. I have the 4NEC-2 file for the turnstile, but obviously still haven't figured out the phase shift issue. I think circular polarization is the way to go for FPV projects, I just wish I could model the antennas before I build them.
Posted 06 January 2011 - 05:26 AM
SY w1seg=5, w1x1=3.125, w1y1=0, w1rad=0.0394
GW 1 w1seg -w1x1 w1y1 w1y1 w1x1 w1y1 w1y1 w1rad
SY w2y1=3, w2z1=0.2
GW 2 w1seg w1y1 -w2y1 w2z1 w1y1 w2y1 w2z1 w1rad
GS 0 0 0.0254 ' All in in.
EX 0 1 3 0 1 0
FR 0 1 0 0 Freq
Posted 06 January 2011 - 10:07 AM
Posted 06 January 2011 - 02:48 PM
I am trying to develop a few different circular antennas. Sure I could copy a circular patch, deal with the 2:1 VSWR of the helical, fly the skew planar wheel and call it a day, but that's not my style. I want to improve my head mounted base station. I just want to get 3/4 mile out of it reliably. I think a turnstile with a reflector will do that... maybe. There's also the cloverleaf, as well as a new antenna of my own design.
I have also been considering a turnstile made from two loop dipole antennas to give me a little bit better control of VSWR in regards to hitting the desired bandwidth, but making 3 baluns would be a royal pain...
Posted 08 January 2011 - 01:48 PM
Posted 10 January 2011 - 06:46 AM
I just purchased the ARRL antenna book. You know you are a geek when you anticipate an antenna text book in the mail
Posted 25 February 2011 - 02:07 AM
Note that this is for a 1280 Mhz antenna and that the optimized result was:
Leg Length = 67.14 mm
Arc Angle = 81.8 degrees
Arc Length = 121.5 mm
Pitch = 47.1 degrees
(this was for a 0.6 mm dia magnet wire)
For those of you that know how to run 4nec2x, here is the file: