Validating the Skeletal wire biconical antenna

We recently investigated the ?Skeletal wire biconical antenna? (often refered to as the wire biconical) as a useful EMC antenna for Antenna Magus. As part of the validation process we wanted to compare the simulation data with measured data but we faced a slight problem. In order to balance the feed of the physical antenna a balun is required which has to be placed in the center between the two cones, physically separating them. This cannot be accounted for in the simulation as it has to be fed using a single port. We wanted the physical model and the simulation model to be as similar as possible. Another alternative that we considered was to feed the antenna from the side through the center of one of the arms – but that introduced other uncertainties and non-symmetry issues.

Image of the Skeletal wire biconical antenna

Image of the Skeletal wire biconical antenna

Eventually we decided to build a wire monocone using the same dimensions as the biconical antenna, replacing one of the cones with a ground plane. Skeletal wire biconical antennas are usually designed to operate between 30 ? 300 MHz and are used in EMC applications but we decided to frequency scale the design by 3 times in order to reduce it to a more practical size. Once we finished building the wire cone section, we relised that in spite of our efforts to reduce the antenna?s size we still needed a +- 3m diameter ground plate if we wanted to simulate an infinite ground. Someone came up with a clever plan to instead of using a solid metal ground to use six 10m wires which are placed in the symmetrical plane perpendicular to each element of the cone. This would have the same effect as using a solid ground plane. The following picture shows the final antenna being measured on the roof of the Stellenbosch engineering faculty.

A few risked their hands to help with constructing the antenna while I?m holding the blow torch. : )

A few risked their hands to help with constructing the antenna while I?m holding the blow torch : )


Rooftop measurement with the 10m wires running along the roof.

Rooftop measurement with the 10m wires running along the roof.

The conditions weren?t ideal as it was pouring with rain while we had to do the measurement. We were quite surprised how well the 6-wire ground plane worked! Perhaps the wet roof had enhancing ground plane effects?

The graph below shows measured and simulated s-parameters of the antenna. It was interesting to see the resonance at 850 MHz is not a computational discontinuity but is picked up by the measurement as well. Some investigation shows that the resonance can be moved out of band by adding a short between one of each cone?s wires and the center wire.

S-parameter comparison of the Skeletal monocone antenna.

S-parameter comparison of the Skeletal monocone antenna.

Author: Robert Kellerman

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2 Responses to “Validating the Skeletal wire biconical antenna”

  1. MARCOS DONIZETI says:

    Dear Sir. send me details of mono conical antenna . ok

  2. Marcus says:

    Your ?Validating the Skeletal wire biconical antenna? isn?t correct. Why:
    The original antenna was a bicone antenna, equipped with a very well balanced ?balun?. Yours was not even a discone antenna, and we can?t see a ?balun?. If you decided to direct feed with a coaxial cable, then you must show a detailed picture of connection of the feeder to antenna. The distance is very crucial and even 0.5mm make a difference for a WB antenna. You are comparing apples with oranges in a very crude way. You do not need more than a person to assemble and there is no need to burn hands. We use a cardboard. Draw a hexagon. Open 6 holes at sides and one more at the center. Connect all the wires at the end point. Secure with a thin wire and ?construct? it.
    We have seen many Doctorates thesis, with a very well theoretical illustration based on copy and paste references literature. A wage experimental part, and not convincing conclusions. Is the life an illusion and deception?

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