Canvey Island, Essex, England Justin@g0ksc.co.uk
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Twin boom quad
144MHz LFA Yagis
144MHz LFA Yagis

Low Noise LFA Yagis designed by G0KSC free to build for personal use.

144MHz LFA Yagis
70cms LFA Yagis
70cms LFA Yagis
Twin-Boom G0KSC Quads
G0KSC Twin-Boom Quads
Twin-Boom G0KSC Quads
G0KSC Custom Dish feeds - Above installation @ HB9Q
Custom low-noise dish feeds
Custom low-noise dish feeds
G0KSC Custom Dish Feeds

Above installation @ HB9Q

G0KSC Custom Dish feeds - Above installation @ HB9Q
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3el 4mtr 28Mhz Quad

G0KSC SC2803Q 3el 28Mhz OWA Quad Antenna with a 4 Metre Length Boom

This antenna produces 9.34dBi ofr forward gain with 32dB front to back ratio at 28.500 Mhz. This has been achieved over a respectable 500 Khz bandwidth on a boom of only 4 metres in length. This is around one metre+ less than would be required to see similar gain from a Yagi. In addition, I have been able to model the antenna without the narrow bandwidth characteristics normally associated with an antenna of this kind.

Bandwidth is a little smaller than on 50 and 70 Mhz as we are still using 2MM wire. If this was increased (which would need re-modelling) the bandwidth would be greater.

As with all my antennas, this is a non-critical design and therefore, any small errors in you calculations when building the antenna WILL NOT have a great impact on the antennas final performance.

Dimensions in Metres

Element spacing:

  • Ref =      0
  • Driven =  1.8
  • D1 =       4

Elements lengths - full quad length:

  • Ref =       11.128
  • Driven =   10.752
  • D1 =       10.328

Performance figures @ 28.500Mhz:

  • Froward Gain: 9.34dBi free space
  • Front to Back: 32.13dB
  • Radiation angle at 10 Metres above ground: 15 degrees

 

Element diameter:

This antenna has been models with 12#/ 2.05MM copper wire. You will need to mail me if you wish to use a different gauge as the model will change. Isolated spacers will be needed. fiberglass would be a good option.

NOTE:

Build orientation is as per the layout image below with the feed point on the bottom section of the quad indicated by a red circle.

Feeding the Antenna

Whilst OWA is not normally a term used in quad antennas, I felt it appropriate due to the low SWR and wide bandwidth of this antenna. Like all of my antennas, this has a 50Ohm impedance so can be fed directly with 50Ohm coax, no matching is required. However, a balun or RF chokes should be used in the coax as close to the feedpoint as possible.