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I have been working on a custom drone for quite some time now. One thing I have found an issue with is the remote control antenna orientation in relation to the drone. In some directions I will get absolutely no signal. (The antenna type pictured below).

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On the receving end, I am using a standard NRF24L01+ with a PCB antenna.

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Eventually, I would like to add another PA+LNA version to the drone with a lightweight antenna such as this.

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Is there a better antenna design that will give me omnidirectional transmits and receives? On the remote control I do not care about weight so they can be as heavy as they like, but I would like to keep the weight as little as possible on the drone, which is why I bought the "wire-like antenna".

I know that each antenna needs to be used for a correct frequency, in this case 2.4Ghz, but other than that I do not know much about wireless antennas.

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  • \$\begingroup\$ This is not an answer, but you might try 2 antennas placed at 90 degree angles with a common center point to connect to. With 3 you can do X, Y and Z axis from a common point. At these and higher frequencies great omni-directional performance with one antenna is all but impossible. Look at any cell-phone tower and see how they have many antenna's pointed in all 8 to 16 compass points. \$\endgroup\$
    – user105652
    Commented Jun 23, 2018 at 4:10
  • \$\begingroup\$ Those wire antennas are fine; have a look at drone antennas specifically. Omni for a moving drone is NOT the same as for a stationary omni. Stationary omnis have two zero-signal points, directly above and directly below. These are still fine for a car, but not a drone. Alternatively, google how airplane antenna arrays are arranged. A full-wave 2.4GHz antenna is 12.5cm (lambda=300/2400), but you can get decent results with 5/8. Don’t use quarter-wave, 5/8 is better. Any piece of stranded copper or silver wire is fine when soldered to a UFL connector. \$\endgroup\$
    – user2497
    Commented Jun 23, 2018 at 7:38

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Ideally for a omnidirectional antenna the radiating element must be perpendicular to the ground. Wi-fi units don't kick out a lot of power usually about a 1/10th of a watt give or take. In order to have best results a high gain vertical antenna and mounted as high as feasible at your location. A good choice for antenna are colinear antennas as they direct the signal toward the horizon for maximum usable range. Gain is measured in db or decibels which is a logarithmic scale. Every 3 db is a doubling of signal. Here are 2 links with formulas and construction information. Enjoy... :)

http://wireless.gumph.org/articles/homemadeomni.html

http://martybugs.net/wireless/collinear.cgi

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All antenna types that you have shown have some directivity, and its impossible to design a perfectly omnidirectional antenna (which is called isotropic antenna).

But this might not be your only problem: There‘s a thing called fading, which is the signal reduction caused by interference. Usually, fading is not a big problem for moveable objects, because fading is a local thing. But a drone can also stay at some place for some time.

Both problems (directivity and fading) have a simple solution: A second antenna with a position and angle offset. So you might want to use a second antenna on the drone or the receiver.

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