Antenna Alternatives

   Antennas now has its own section in the Forums



  There are alternative antenna choices for your UAV when space is a consideration. RHCP antennas are without doubt one of the best choices you can make for your video and telemetry signals. I had wanted to use a RHCP antenna for telemetry for my X-8 but the choices I had come across were pretty space demanding. Surfing the web doing some antenna research I ran across these wheel antennas from Kent Britain WA5VJB, a fellow amateur radio operator.  He's got some really useful designs other than the wheel.
   I purchased 2 of the 900 mhz variety for the telemetry, one for in the X8 and one for the ground station . Since the plan is to install all antennas within the X8 these are a great space saving choice over the current offering of cloverleaf antennas. The 900 mhz wheels measure about 4.5 inches in diameter, somewhat smaller than a CD ROM and only slightly thicker. The best part being they are only $ 12.00 each. They can be fed with coax directly or as seen in the photograph you can solder a circuit board SMA connector of your choice to the center in the holes provided.
   These wheel antennas are considered to be horizontally polarized at the plane of the horizon however as your UAV gains altitude the wheel antenna emits a cross polarized signal. Here is a quote from “Around 1990 the first launch of a balloon borne payload in the Denver, Colorado Area took place sporting a Little Wheel as the radiator for the on-board ATV transmitter. It was found to work quite well and had some interesting attributes that were previously undisclosed. Those being that the Wheel antenna although being a horizontal radiator on the horizon displayed properties of cross polarization above and below the array - similar to two in phase horizontal dipoles. This worked to the advantage of the ground station by employing a circularly polarized antenna (Helix) - also a fixed horizontal antenna directly below at the launch site would not see the up to -30 dB nulls as the balloon rotated. The horizontally polarized tracking antennas (Yagis) were receiving a signal of constantly changing polarity as the payload rose to an altitude at which it would start to drift away from the launch site and the horizontally polarized tracking antennas would become more effective due to the horizontal polarization emitted from the sides of the Wheel. The pattern of the Wheel is within +/-0.5dB of being a perfect circle in the E-plane. In the H-plane the pattern is +/-35 degrees of the horizontal axis of the antenna. These figures equate to ~ 4.28 dBic gain or 6.38 dBdc. The dBic gain above and below the array is somewhat indeterminable due to the fact that the circular polarization exhibited is quasi-circular or cross polarized; however, it responds to a Helix in a manner consistent with the gain of a pair of like sense Helices in a system looking at one another. ”

  This antenna does radiate well (60% efficient) and also radiates well in the second and third harmonics so take precautions to provide filtering for your transmitter.
  You’ll want to use a “Wheel” antenna on each side of your link as losses will result if mated to just a dipole when your UAV is overhead. Just mount it in a horizontal position at each end of the link. If it fits inside your UAV that’s great but it could also be mounted flat on the wing as well.


Holes are provided for SMA circuit board jack mount
or direct connection to coax.










This link shows the antenna being tested in a 3D pattern.


 i'll post my actual installation once I get there.

Keep experimenting with radio, get your tech license, it's easy and you'll be contributing not only to this great hobby but ham radio as well. 



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  • Thanks jake, it doesnt seem that hard. Hopefully it will work
  • Hi Edge,

    This is a list of all of Alex's tutorials. Hope they help you come up with a solution.

  • @ Gisela & Joe Noci
    i have an epp flv plane and i bought the same xbee pro868 module with a wire antenna and stock antenna on ground. İ have terrible range 300 m maximum. İ dont have a working knowledge of antennas. Can you direct me where i can get/how i can make dipole antennas you mentioned. İ am tired of xbee losing connection every flight. İ would really appreciate if you could help.
  • @ Joe , Peppe and James Sowell

    Chris Anderson has added an "Antennas" section to the Forums. Should be good place to collect all discussions regarding antennas and radio transmission.

    Please visit and share your knowledge and set ups with photographs there.

  • @ joe

    Awesome, can't wait to build one.

  • @ Geoffrey

    I bet you used exhaust tubing for the rings ---- The DDRR has very high currents flowing in the vertical post and ring with very high (KV) voltages over the tuning capacitor - the radiation resistance of the antenna can be measured in values less than a few ohms, so any milliohm connection in the rings are a huge loss..They are not practical for the HF bands.

    Here are ( I hope) some pics of the 1/2 wave ring radiator - just took them of the prototype we used in the EMC chamber - the production antenna are not here at home - at the salt mine. Hope the pics turn out.








  • @ Joe

     yes I am a amatuer. KB6WSQ is my call sign.

    Thanks for the antenna info and links. Please send me or post a photo of your (quasi) DDRR. I experimented with this antenna 30 years ago after seeing it in QST magazine...didn't work for me on 40 meters, oh well.

     Keep the discussion going and the ideas flowing, the DIYDrone community can benefit from it. Maybe even encourage a few to get their ham license.

    I posted a question on the ardustation forum about using antenna tracking, in reverse, by having a small beam or log periodic follow the ground station location from a moving UAV.

  • very good, Joe...

    now, it's more clear and I totally agree...... and maybe we had QSO B4 too...eheheh

    I try to use the same skills in every field of telecomm's, sharing experiences, just to get the best obtainable, even with poor means... raising tenth of dB as in EME traffic.....

    really, I'm landed on "RC model land" less than 1 year ago... just to help my friends with radiolink...

    and CQWW is coming....


    Giuseppe "Peppe" Solimano, I8UZA

    and also VP5I, KJ4UMJ (extra), IH9P, P48K, etc.

  • @Geoffrey,

    Hi, actually , the DDRR is a slight misnomer for the final antenna in use - The DDRR in its more or less true form can be found here:

    But what I derived is more a 1/2 wave ring radiator - it is a 1/2wave ( at the freq of interest) length of 'wire' formed into a circle. Now, if you space this some distance above a full wave diameter sheet of conducting material, and add a conducting support pillar between ring and plane. Now connect the RF coax center to the ring at a point some mm away from the conducting pillar, and the shield to the ground plane below that point. Then move the ring closer to or away from the ground plane at the point directly opposite the coax connection and support pillar. - this changes the capacitance between the ring and the ground plane, tuning it. There are certain 'rules' of thumb for the height above the ground plane etc. What we now have is a 'slot' antenna. The slot formed between the ring and ground plane is in fact what radiates the energy, and tis allows us to get rid of the ground plane. We do this by 'rolling' the plane up into a cylinder beneath the ring, the same diameter as the ring, spaced the same distance from the ring as the plane originally was. then we can reduce the 'length' of the cylinder...and presto, we can simply replace the ground plane with another ring of wire, the same diameter as the upper ring. So at 868MHz, as I have done, 'winding' the wires of the two rings onto a polyethylene former ( the dielectric constant makes the rings smaller than they would be in air), the rings are 48mm diameter, and spaced 7mm apart.

    I read in your postings an intimation that you are a radio ham? if so, or even if not, have a look in the RSGB VHF/UHF manual, 4th edition, pages 8.35 and 8.35 they give examples and formulae....Also RSGB Radio communication Handbook6th edition pages 13.33 and 13.34.

    It is a vertically polarised antenna, gain around 1dbD ( 1dB more than a dipole...)


    Joe De V51JN/ZS6JGN

    DDRR Antenna Simulation
  • @ peppe

      I too have an X-8 but it is still in the box while I sort out my antenna scheme (test the antennas on a CTH Deep reaper first).

     Keep the antenna discussion going by adding positive practical information, between You, Joe and myself we have over a 100 combined years antenna experience and I'm sure the community can benefit from this discussion. Especially if we add test results, photographs and encourage experimentation.

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