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About IBCrazy

  • Rank
    RC-Cam Visitor
  • Birthday 12/31/1981

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  • Location
    Amherst, Va
  1. Ok, this is for MR RC-CAM. This is the Turnstile over reflector antenna he has spoken about, well, sort of. I never saw cyberFlyer's antenna. I used vector phasing to obtain a .98 axial ratio without any kind of phasing system to match it other than the reactive vectors of round wire. The reflector was the killer. That's where Hugo came in. Hugeone helped me in modeling this one and tweaked it to perfection since I couldn't seem to simulate the ground plane properly. The cool thing about this antenna: you can adjust the gain for between 5 and 10 dbic. I only have it perfected for 9
  2. I am going to ry the series transmission line method that your described, Terry. I was looking into the ARRL handbook and it seems that to get a 50 ohm match, I need to make a strip where: H/W = .625 I computed that from Zo = 138log(4H/d) for a single wire over infinite ground plane. So if I keep the input feed short enough that resonation isn't a problem, I can run it a short length vertically and then run the strip 90 degrees perpendicular to it. My question is whether the whole strip needs to be that height or if it should wind upward and finish at that height? Any idea? -A
  3. Interesting.. I might have to try that. I used a galvanized steel triangle that is 1/8 wavelength tall and 1/2 wavelength long for the first 1/2 turn. The hypotenuse of the triangle follows the helix pattern while the long leg is parallel to the reflector. Dalbert02 did some testing by compressing the coil a bit and got favorable results with the steel sheet matching stub. I wonder what cutting the center of the refletor out would do so there would be a hole as big around as the helix? Would that lower the impedance?
  4. Helicals are fairly easy to make and are durable, but obtaining good SWR is not easy. The impedance runs about 140 ohms or so. dalbert02 has one of mine for 1280MHz that I made around a 2.5" PVC conduit former. I tried using an impedance transformer to help with the VSWR issue, but the best I could do was 2:1 VSWR. Also the plot was like nothing I had ever seen before. Perhaps dalbert can put the picture of it up here? I'd be interested in what you guys think. I might make another one to send down to him for a plot curve using a crossed wooden former. Dave, can you post the plots
  5. I'm working on it, still. I have a bunch of other CP designs I plan to try. I have been sending my antennas to Florida for testing. I just purchased the ARRL antenna book. You know you are a geek when you anticipate an antenna text book in the mail
  6. The helical has been a pain for me. I can't get the VSWR below 2:1... I have had great luck with the skew planar wheel, though. 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
  7. This is the 4NEC-2 file I can't get to recognize the second voltage source. I have it for 910MHz: CE 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. GE 0 EX 0 1 3 0 1 0 GN -1 SY Freq=910 FR 0 1 0 0 Freq
  8. 4Nec-2 is driving me nuts. I cannot figure out how to model a phase shifted antenna. I wanted to model a turnstile antenna with a reflector for 1280MHz. I can't seem to figure out how to get it to figure a 90 degree phase shift stub. I can use two separate sources, but then the program only recognizes the one source and ignores the second. 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 ab
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