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

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

G0KSC Twin-Boom Quads
Custom low-noise dish feeds
Custom low-noise dish feeds
G0KSC Custom Dish Feeds

Above installation @ HB9Q

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G0KSC SC0405S 5el 70Mhz Yagi Antenna with a 2.55 Metre Length Boom

This is a nice compact good gain 70 Mhz beam. It has a short length boom which is made from a single piece 1inch square tube section. No boom support will be required.

This antenna shows good performance particularly Front to Back. The antenna covers all of 70Mhz to 70.5Mhzwith good gains and SWR throughout. with a nice short 2.55 metre boom, it should not be difficult to set up on a nice hill top somewhere!

This is a 5el Yagi that is shorter than 'ideal' and therefore a little radiation resistance exists. Although not the end of the World, for every 100 Watts at the feed point, 1.2 Watts will be lost. Nothing compared with non-OWA designs admittedly. However, this one has been deliberatley designed short to provide a compact antenna that exhibits good gain. 

Dimensions in Metres

Element spacing:

  • Ref =      0
  • Driven =  .375
  • D1 =      .562
  • D2 =      1.522
  • D3 =      2.548

Element sizes per element half:

  • Ref =       1.061
  • Driven =   1.047
  • D1 =       .991
  • D2 =       .97
  • D3 =       .938

Performance figures @ 70.200Mhz:

  • Froward Gain: 10.2dBi free space
  • Front to Back: 26.2dB
  • Radiation angle at 10 Metres above ground: 10 degrees

Element diameter:

Each element is made out of single piece 1/2 inch (12.7mm) aluminium 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 1inch or 1,1/4 inch boom as the elements sit high enough above the boom for the boom to have no influence.

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 SC14408L 8el 144Mhz Yagi Antenna with a 3.4 Metre Length Boom

This antenna has been redesigned and represents what i beleive to the the 'ideal boom length' for an OWA direct feed 50 Ohm Yagi with 8 elements on 144MHz. 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 very low-noise pattern.

 

The model below is designed with 12.7mm / 1/2 inch elements. 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 VERY different diameter wire and get the best performance possible, Spacing and element diameters MUST be re-optimised.

REMEMBER, Gain does not make the best antenna on 2m. F/B, SWR Banwdith, Pattern Stability, Side Lobe suppression, Sky Teperature and G/T all play a role. Choose an antenna and gain alone and you will never know what you are missing!!

 

 

SC14408L by M5TAW

 

 

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

Element spacing:

  • Ref =      0
  • Driven =  .360
  • D1 =       .495
  • D2 =       .877
  • D3 =      1.419
  • D4 =      1.993
  • D5 =      2.683
  • D6 =      3.418

Element sizes per element half:

  • Ref =       .5055
  • Driven =   .504
  • D1 =         .471
  • D2 =         .456
  • D3 =         .440
  • D4 =         .4325
  • D5 =         .422
  • D6 =         .3975

 

Performance figures @ 144.300Mhz:

  • Froward Gain: 12.80dBi free space
  • Front to Back: 26.83dB

Sky Temperature @ 144.100MHz = 247.5 Kelvin

G/T @ 144.100MHz = -11.17dB

 

 

Dimensions in Metres - all tubing 12mm diameter, mail for other sizes and tapered elements

Element spacing:

  • Ref =      0
  • Driven =  .360
  • D1 =       .495
  • D2 =       .877
  • D3 =      1.419
  • D4 =      1.993
  • D5 =      2.683
  • D6 =      3.418

Element sizes per element half:

  • Ref =       .5065
  • Driven =   .504
  • D1 =         .472
  • D2 =         .457
  • D3 =         .441
  • D4 =         .4335
  • D5 =         .423
  • D6 =         .3985

 

Performance figures @ 144.300Mhz:

  • Froward Gain: 12.78dBi free space
  • Front to Back: 26.76dB

 

Azimuth Plot

 

 


Elevation Plot

 

 

This fantastic antenna at 10m 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!