Universal antenna types are the ones which design is being used for many bands (all antennas with different proportions can be used for all the bands, but there is the question of practicality). They are well tested and mostly quite old designs, well before computer simulation. However, they are still widely in use today, and that trend will continue. In this section we will explore simple dipole antenna and its variations, monopole, Yagi, Biquad, 3D corner and a bit more exotic HB9CV antenna.

dipole inverted V delta loop  ground plane antenna  vertical monopole antenna  yagi folded dipole
2-element yagi  universal hb9cv  universal biquad antenna  universal 3d corner

3D corner antenna was designed in the 1970s, and is very often used, even for military radars. The design given here is a modification by Dragoslav Dobricic. The modifications from the original design are smaller antenna and lowering the impedance with one director (the same principle is used with Yagi’s) which has as a consequence improved gain.

The antenna is practical for many bands, with slight modifications. For higher frequencies, 3D corner is one of the best feeds for offset parabolic satellite dishes.

Its mechanism of work can be split into two parts: reflector and monopole with director.

Reflector is known as Corner Reflector – three perpendicular flat conducting surfaces that reflect waves. For the maximum gain, antenna should be tilted by 45°.

01 3d corner

Corner Reflector surface showing how it reflects different waves from all three surfaces


Yagi-like part consists from a monopole and a director.

Reflector can be of any size, keeping in mind that its size directly affects gain. Its optimum size is at 2.8 wavelengths for one side, for which the gain is 18dBi. Larger reflectors do not give significant increase in gain. Very good 16dBi can be obtained with 1.8 wavelengths.

Reflector side [λ] 1.2 1.4 1.8 2.3 2.8 3.8
Gain [dBi] 12 14 16 17 18 18

 

02 radiation pattern 03 radiation pattern

Horizontal and Vertical radiation pattern

Reflector should be made from 1mm thick aluminum plate for higher frequencies, or with net wire with density 0.1 wavelengths for 23cm band or lower frequencies. In some cases, because of the high wind resistance of the antenna, a metal frame is required.

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Legend (all dimensions are in mm):

  • m – monopole length,
  • d – director length,
  • w – net wire density,
  • r – minimum reflector thickness,
  • h – director and monopole thickness,
  • x – monopole distance from reflector surfaces,
  • y – director distance from reflector surfaces,
  • R – length of a side of the reflector.
Band Frequency [MHz] Wavelength Reflector
12dBi 14dBi 16dBi 18dBi
2m 145 2070 2484 2898 3726 6210
70cm 435 690 828 966 1242 2070
23cm 1296 230 276 322 414 690
2.4GHz 2430 123 147 172 221 369
5GHz 5600 54 65 76 97 162

It seems that antenna is not usable at lower frequencies, for example for 2m band, but that might not be true if we can make use of some existing construction. However, the reflector that gives over 12dBi is not likely to be used.

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 04 blueprints

3d corner antenna photo

3d corner antenna photo

This antenna is made from two elements but the gain is about the same as the 3-element Yagi. At lower frequencies, where the elements are quite large, one can see that this antenna has the huge advantage in price, weight and wind resistance. The gain is approximately 6.5dBi. The only small drawback is the need for a capacitor for tuning the SWR.

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HB9CV antenna. Theoretical measurements without corrections are given in green, with corrections are marked with blue letters.

Put the capacitor on a hot-wire lead.

  • R – Reflector length,
  • S – Length of the Radiating element,
  • A – distance between R and S, center to center,
  • RS – distance from the line of the symmetry of the antenna and the point where the phasing line is attached to the R,
  • SS – distance from the line of the symmetry of the antenna (line that passes through the center of the boom) and the point where the phasing line is attached to the S,
  • C – Approximate capacity for which the best SWR can be achieved. It is best to use variable capacitor to find the exact capacity, and then replace it with fixed capacitor.

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03 radiation pattern 02 radiation pattern

Radiation pattern in Vertical and Horizontal plane

Biquad

Biquad antenna is also known as Double Quad Beam or some call it Bowtie Beam antenna (Bowtie Beam is also the name for the subtype of the Biconical antenna). It is widely used because of its properties:

  • Compact and thus can be portable,
  • Easy to make,
  • Cheap,
  • Only one radiating element and reflector,
  • 11dBi gain,
  • SWR as low as 1.05 if made ideally,
  • 50Ω impedance,
  • Equal radiation pattern in horizontal and vertical planes,
  • Good bandwidth, better than Yagi.

Dimensions of the reflector are not crucial. By Trevor Marshal, it should be .9 x .9 of the wavelength, but it was discovered that 1.2 x 1.6 wavelengths gives the largest gain. In the table we will list both values (the larger reflector will give us less than 1dBi gain over the smaller one). Distance of radiating element from reflector is from the center of the wire.

  • w – Reflector width,
  • h – Reflector height,
  • x – Outer Side Length,
  • y – Inner Side Length.
  • All measurements are in mm.

01 biquad

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02 radiation pattern 03 radiation pattern
04 radiation pattern

Radiation pattern in Vertical and Horizontal plane. Image below: in 3D

Orientation and polarization are not intuitive as with Yagi antenna. See the image for proper orientation.

05 biquad orientation

There is no antenna with better gain/expense ratio than the 2-element Yagi antenna. The Dipole alone gives us 2.15dBi. As we can see from the radiation pattern, the maximum gain (in the direction of the x-axes) is 6.5dBi, a gain in over 4dBi by just adding a reflector or a director! By adding one additional director we will have only approximately 1dBi more.

For the lower frequencies, where the dimension of the antenna becomes quite significant, as well as its price, it is obvious that adding that additional element does not pay off.

06 3d 07 radiation pattern


3D model of Yagi 2 antenna and radiation pattern in 3D

08 radiation pattern 09 radiation pattern

Radiation pattern in Vertical and Horizontal plane

There are two variants of the Yagi 2: with Reflector and without Directors and with one Director but without Reflector. If the value in the last column is larger than for the Radiator-Dipole, then it is the measure for the Reflector, and vice versa – Reflectors are always longer than the Dipole and the Directors are always shorter.

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There is a need for an appropriate BalUn. See more in the BalUn section

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