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Thread: Are circular antennas really needed for ground FPV?

  1. #11
    Just dog tired. Wearyman's Avatar
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    Generally speaking, CP is pretty much always better.

    HOWEVER, as some of the more experienced pilots here will tell you (not me, I'm just parroting them) CP isn't always strictly required.

    The biggest issue with CP in ground applications is the big freaking antennas. Particularly in the 1.2/3 ranges and down. They are large, get caught on objects the truck is passing by or through (like shrubs and branches and sticks) and are VERY easily damaged when you inevitably roll the vehicle. (And you WILL roll an E-Revo. ALOT.)

    You may be better (and more cheaply) served going with a good quality linear setup, such as an IBCrazy Vee antenna on the truck and a linear patch, BiQuad or Yagi on the ground station for penetration. The Vee is going to give you excellent range, and can be mounted on a raised mast above the truck using an antenna cable extension.

    Personally I get fair range just using the craptastic rubber duck antennas that my TX and RX came with. They aren't tuned, they are cheaply made and are probably the literal worst-case scenario for antennas. But I can go around my block, transmitting through 10 houses and still make out a picture. (It is NOT great, but it is usable.) So really, you could even stick with the basic antennas while you are trying out your FPV rig. Once you reach the limits of the rubber duck antennas, then look into a better linear setup.

    Have fun!
    FPV - The World is My Airfield

  2. #12
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    I fly mostly linear on 1.3 as it's my long range setup. video is perfect. on 5.8 it's mandatory for a usable picture.

    my advice. try the stock whips first and go from there.

  3. #13
    Size matters c5galaxy engineer's Avatar
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    Multipathing isn't always bad as sircana says. I watched a friend fly a quad under a concrete bridge and then assend up the other side of it (out of LOS). On the other side of the bridge was a rock cliff with a waterfall. He was flying between the bridge and waterfall and it was the shittiest video I have ever seen……It was all multipathing. I made a comment about it and he just calmly said ''at least its an image''. It made me change my thoughts on video image and flying. He was depending on the multipathing to get through a short LOS-less area. As soon as he emerged above the bridge the video was fine as he expected.
    Last edited by c5galaxy engineer; 13th November 2013 at 04:32 PM.
    Brett Hays
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    flitetest.com/articles/fpv-full-scale-cockpit-ground-station-w-42-tv

  4. #14
    Instructor Pilot
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    Are circular antennas really needed?

    Quote Originally Posted by c5galaxy engineer View Post
    Multipathing isn't always bad as Circanna says. I watched a friend fly a quad under a concrete bridge and then assend up the other side of it (out of LOS). On the other side of the bridge was a rock cliff with a waterfall. He was flying between the bridge and waterfall and it was the shittiest video I have ever seen……It was all multipathing. I made a comment about it and he just calmly said ''at least its an image''. It made me change my thoughts on video image and flying. He was depending on the multipathing to get through a short LOS-less area. As soon as he emerged above the bridge the video was fine as he expected.
    Who is Circanna?

    A circular Sircana?

    Cool story bro. Cool story.

  5. #15
    Size matters c5galaxy engineer's Avatar
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    Geeeeezus……..Zee! Thats what you gleaned from that story…..my poopy spelling…..LOL. Yes…..Sircana…..LOL. To funny! A-hole
    Brett Hays
    JosephOregon.com
    flitetest.com/articles/fpv-full-scale-cockpit-ground-station-w-42-tv

  6. #16
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    Quote Originally Posted by c5galaxy engineer View Post
    A-hole
    I try my best.

    I think I generally do a pretty good job at it.

  7. #17
    Navigator jrwperformance's Avatar
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    Cool...thanks for the replies. I tried my 1.2 with a pair of circular antennas ( clover and skew) and walked around my neiborhood with my Goggles like a dork. Was able to go just about anywhere with a good signal. Far beyond my 5.8. Was suprised at how many houses and trees it goes through. I tested again with the stock antennas with about the same results. I'm sure this will go a full mile without issues.

  8. #18
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    I wass able to fit my 1.3cp under the body of my Traxxxas Summit otherwise I would have just went with Linear.
    Most of the money I made this year I spent on FPV,the rest I just wasted.

  9. #19
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    There is a lot written about similiar questions. For my money ... The Circular-Polarization (CP) gets its extra axis by dividing the power between the two axis (horz and vert) and also radiates off the end so the CP is less than 1/3 the signal of a dipole. The big issue is multipath, (signal and reflection being exactly 1/2 wave length apart and canceling each other.) So the real answer is diversity-reception (two or more receiving antennas spaced 1/2 wave length apart, which also increases the beam width).
    You can also add dipole(s) horizontally to give you immunity from multipath polarization or more gain.

    There is a reason why there are no trucks, cars or emergency vehicles with cloverleaf antennas.

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