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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DualBand 50/70Mhz 4el

G0KSC SC6-4-4DQ 4el 50Mhz/70Mhz Dual band OWA Quad Antenna with a 2.7 Metre Length Boom

About this Antenna

This is a dual band Quad for both 50Mhz and 70Mhz which has just 4 sets of spreaders which each hold a quad element for each band. There are two feed points too, one for each band.The spreaders have been spaced in order to bias the best front to back upon the 50Mhz band and more gain bias upon the 70Mhz band. 

As with most of my antennas, both driven elements provide a 50 Ohm impedance to direct coax connection with no matching unit (or 1/4 wave lengths of coax of another impedance).

This is a great performing antenna for such a short boom length. Very light weight too. Enjoy!

SWR and bandwidth

As we are using a common set of spreaders the SWR can not be as flat as with a single band 50 Ohm quad.

Sizing and spacing are as follows:

Dimensions in Metres

Element spacing:

  • Ref      =     0
  • Driven  =    1.198
  • D1       =    1.758
  • D2      =     2.752

Element sizes per element half:

  • Ref 6     =      6.288
  • Ref 4     =      4.492
  • Driven 6 =      6.096
  • Driven 4 =      4.412
  • D1-6      =       5.552
  • D1-4      =      4.332
  • D2-6      =      6.016
  • D2-4      =      4.232 

Performance figures @ 50.250Mhz:

  • Froward Gain: 9.64dBi free space
  • Front to Back: 21.08dB
  • Radiation angle at 10 Metres above ground: 10 degrees

Performance figures @ 70.250Mhz:

  • Froward Gain: 10.41dBi free space
  • Front to Back: 12.04dB
  • Radiation angle at 10 Metres above ground: 5 degrees

 

Element diameter:

This model is created with 2mm thick copper wire

 

For construction information see 'G0KSC insulators' and the UKSMG article from the main menu on the home page.