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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G0KSC SC2807M 7el 28Mhz Yagi Antenna with a 14 Metre Length Boom

This antenna has been designed for someone who loves 28mhz and who has a bit of space too! Working the WHOLE BAND from 28Mhz to 29Mhz, not just the CW or SSB portion. With great gain and front to back ratio to boot. Power limitations are whatever the limit of your coax is so if you have good coax, 3KW+ is not a problem.

Mechanical Construction

This Yagi has been designed to be built on a boom of 3 sections. The centre section should be a 5 metre length of 2 inch aluminum tubing whilst the out 2 sections should be 1, 3/4 inch tubing slotted in to the 2 inch section by around 600mm each end. Boom guying to the main mast will be required.

If G0KSC insulators are to be used, these should be engineered to be 300mm long rather than 100mm and the width of each also should be doubled.

Small errors in your measurements or calculations when building this antenna WILL NOT greatly affect performance due to it's non-critical design.

Dimensions in Metres

Element spacing:

  • Ref =      0
  • Driven =  1.719
  • D1 =       2.468
  • D2 =       4.668
  • D3 =       7.899
  • D4 =       10.996
  • D5 =       14.089

Element sizes per element half:

  • Ref =       2.619
  • Driven =  2.564
  • D1 =       2.444
  • D2 =       2.397
  • D3 =       2.367
  • D4 =       2.364
  • d5 =       2.256

Performance figures @ 28.500Mhz:

  • Forward Gain: 12.35dBi free space
  • Front to Back: 22.1dB
  • Radiation angle at 10 Metres above ground: 15 degrees

Element diameter:

Each element is made out of single piece 1/2 inch (12.7mm) aluminum tubing Each element half length needs to be doubled in order to gain your total element size. No difference is length needs to be calculated for the 2inch or 3 inch boom as the elements sit high enough above the boom for the boom to have no influence.

If you are only able to obtain 1/2 inch elements in 6 metre lengths and can only obtain 5 metre lengths, join them in the middle at the insulator with a small piece of 3/8 inch tubing (600mm long) bolt the element to the insulator with 2 bolts either side of the boom.

NOTE:

You can build this antenna with 13mm diameter tubing using the same parameters above. Slightly higher front to back ratio and forward gain will be seen along with a narrower SWR curve.

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

 

G0KSC SC0606L 6el 50Mhz Yagi Antenna with a 6.75 Metre Length Boom

Updated June 2010

Please read the whole page, there are several versions of this antenna listed. If you do not the the diameter tubing you need to have this in or require tapered elements, Email me!

This antenna is not recommended for use in noisy city locations due to the elevation pattern. This is not a fault with this antenna, it is a characteristic of this boom length/ Wavelength

 

This antenna has been redesigned and represents what I beleive to the the 'ideal boom length' for an OWA direct feed 50Ohm Yagi. This can be seen in the model in the super flat SWR, the high levels of F/B ratio along with the excellent gain and pattern.

 

The model below is designed with 12.7mm / 1/2 inch elements and a 12mm element version. If you require a version of this antenna with another diameter wire, Email me and I will remodel. It is NOT POSSIBLE to simply resize the elements when using a different diameter wire and get the best performance in my opinion, I remodel the whole antenna each time. Element positions also need to change for the ideal antenna to be achieved again. Please read all the way down this page, there are other versions of this antenna using tapered elements too. As I have more requests, I will remodel in other element diameters and tapers and pulbish those too.

 

 

Fabio IZ3GFZ built the SC0606L for 50MHz

 

 

 

Dimensions in Metres - all tubing 1/2 inch or 13mm diameter, mail for other sizes and tapered elements

Element spacing:

  • Ref =      0
  • Driven =  .690
  • D1 =       1.084
  • D2 =       2.535
  • D3 =      4.525
  • D4 =      6.150

Element sizes per element half:

  • Ref =       1.484
  • Driven =   1.4625
  • D1 =        1.380
  • D2 =        1.3445
  • D3 =        1.3295
  • D4 =        1.3115

Performance figures @ 50.150Mhz:

  • Froward Gain: 11.71dBi free space
  • Front to Back: 21.70dB
  • 1:1.1 SWR B/W 500Khz

 

Dimensions in Metres - all tubing 12mm

Element spacing:

  • Ref =      0
  • Driven =  .690
  • D1 =       1.084
  • D2 =       2.535
  • D3 =      4.525
  • D4 =      6.150

Element sizes per element half:

  • Ref =       1.485
  • Driven =   1.4635
  • D1 =        1.381
  • D2 =        1.3455
  • D3 =        1.3305
  • D4 =        1.3125

Performance figures @ 50.150Mhz:

  • Froward Gain: 11.69dBi free space
  • Front to Back: 21.44dB
  • 1:1.1 SWR B/W 500Khz

 

Azimuth Plot


 


Elevation Plot

 

 


This fantastic antenna at 15m up


 

An Excellent SWR to go with the fantastic pattern!

 

Remeber, mail me if you have different diameter tube requirements and send photos of built antenna!

 

 

 

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