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19el 144MHz LN LFA

A Low-Noise 'Urban' 19 element ultra low-noise (close spaced) LFA Yagi for 144MHz

Premium commercial versions of this antenna at Innovantennas

 

Revised  September 2010 V1.1

 

The LFA design has a patent pending and all G0KSC designs are copyright. Any ham can build for their own use or those of a friend. Where profit or commerical gain exists, express permission of G0KSC must be sought.

If you suffer with noise from living in the city, or want the perfect quite EME single antenna or array,  this is another low-noise example from G0KSC

 

This is a 19 element 144MHz LFA Yagi produced using 3/8 inch elements with a 1/2 inch loop section. Other sizes available upon request.

 

This LFA has been designed for maximum suppresion of side, rear and elevation lobes. The result is an ultra clean antenna which will be a stunning performer for 144MHz. The antenna is super wide-band too with an SWR of less than 1.1:1 over more than 1MHz. Uncharacteristically of a Yagi, the LFA maintains F/B over this wide bandwidth and more importantly maintains its pattern too, some example pattern plots are given below for 144.100MHz, 144.300MHz and 144.600MHz. One of the reasons for pattern stablility and bandwidth is the close spacing of the elements on this range of LFAs.

This antenna is particularly good for EME purposes due to the class leading low noise (Sky Temperature) and G/T figures mentioned above. See the bottom of this page for more information.This low-noise property also means less man made noise will be picked up by the antenna too.

I have started to model individual antennas on individual diameter elements in order to achieve the best all round results. Using the same element spacing and changing element diameter has not shown consistant results and therefore, I will spend more time in order to create new models for each (geographic) regions tubing requirements. EUROPEAN versions will follow shortly.

PLEASE NOTE:

  • This antenna WILL NOT show the true SWR in any antenna modelling package unless you are using one which uses the latest NEC4.1 calculation engine. Do not confuse nec versions with EZNEC versions. Unless you have EZNEC pro/4 you are using nec2 NOT nec4
  • There are two sets of measurements listed below. One uses imperial sizes, the other uses metirc sizes. Ensure you use the correct one for the material you have
  • 'within one or two millimetres' Will not do! take the time to ensure you get the spacing ant element lengths as close as you possibly can to the measurements below to ensure good, solid performance
  • Please read the 'how to make the LFA Loop' page here

 

Performance UK/USA Version  -  19 element LFA Yagi

Forward Gain:                                   18.09dBi at 144.100MHz                  

Front to Back Ratio:                         32.05dB at 144.100MHz

Bandwidth:                                       Better than 1MHz below 1.1:1 (143.7 - 144.7MHz)

Sky Temperature:                           211.1Kelvin

G/T:                                                  -5.16dB

Stacking Information:

Vertical Stacking:                             4.95m

Horizontal Stacking:                        5.20m

4 x antenna Sky temp:                    208.9K

4 x antenna G/T:                              +0.85dB

4 x antenna Gain:                            24.05dBi

 

Build Dimensions for UK/US Version

Element   Position (M)     .5 element length in metres            Element Notes

Reflector               0                         .512                      3/8 inch Diameter tube or solid rod

DE1                     .183                     .443                1/2 Tube (feedpoint)

DE2                      .347                    .443                1/2 Tube

D1                        .580                    .4775              3/8 inch  Diameter tube or solid rod

D2                       1.017                    .4475             3/8 inch Diameter tube or solid rod

D3                       1.349                    .4525             3/8 inch Diameter tube or solid rod

D4                       1.986                    .4515             3/8 inch Diameter tube or solid rod

D5                       2.772                    .445              3/8 inch Diameter tube or solid rod

D6                       3.622                     .439             3/8 inch Diameter tube or solid rod

D7                       4.504                     .435             3/8 inch Diameter tube or solid rod

D8                       5.404                     .4315           3/8 inch Diameter tube or solid rod

D9                       6.318                     .4285           3/8 inch Diameter tube or solid rod

D10                     7.240                     .4255            3/8 inch Diameter tube or solid rod

D11                     8.175                     .4215            3/8 inch Diameter tube or solid rod

D12                     9.125                     .416              3/8 inch Diameter tube or solid rod

D13                   10.080                    .4105             3/8 inch Diameter tube or solid rod

D14                   11.025                    .404              3/8 inch Diameter tube or solid rod

D15                   11.994                   .3965             3/8 inch Diameter tube or solid rod

D16                   12.971                   .3875             3/8 inch Diameter tube or solid rod

D17                   13.775                   .4015            3/8 inch Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 8mm tube bent to 'trombone' inside the 12mm tube. You can use 10mm tube also, Adjust loop for best SWR.

Install a 1:1 grounded balun such as Pawsey stub or G0KSC Antenna Balun more Here: http://www.g0ksc.co.uk/creatingabalun.html

Feed point is the centre of DE1

 

 

Please read the 'how to make the LFA Loop' page here

 

Build Dimensions for European Version

Element       Spacing in metres  - Half element Length in metres            Element Notes

Reflector           0                        .5115              10mm Diameter tube or solid rod

DE1                 .182                    .443               12mm Tube (feedpoint)

DE2                 .346                   .443                12mm Tube

D1                   .585                  .4775               10mm  Diameter tube or solid rod

D2                  1.018                  .447                10mm Diameter tube or solid rod

D3                  1.349                  .452                10mm Diameter tube or solid rod

D4                   1.987                  .451                10mm Diameter tube or solid rod

D5                   2.771                  .4445              10mm Diameter tube or solid rod

D6                   3.620                  .4385              10mm Diameter tube or solid rod

D7                   4.503                  .4345              10mm Diameter tube or solid rod

D8                   5.404                  .431                10mm Diameter tube or solid rod

D9                   6.319                  .428                10mm Diameter tube or solid rod

D10                 7.241                  .425                 10mm Diameter tube or solid rod

D11                 8.174                   .421                10mm Diameter tube or solid rod

D12                 9.122                  .4155                10mm Diameter tube or solid rod

D13               10.078                  .410                 10mm Diameter tube or solid rod

D14               11.023                   .4035               10mm Diameter tube or solid rod

D15               11.992                  .396                 10mm Diameter tube or solid rod

D16               12.970                  .387                 10mm Diameter tube or solid rod

D17               13.776                   .401                10mm Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 8mm tube bent to 'trombone' inside the 12mm tube. You can use 10mm tube also, Adjust loop for best SWR.

Install a 1:1 grounded balun such as Pawsey stub or G0KSC Antenna Balun more Here: http://www.g0ksc.co.uk/creatingabalun.html

Feed point is the centre of DE1

 

 

 

The Azimuth Plot 144.100MHz

 

 

Azimuth plot 144.300MHz

 

 

Azimuth plot 144.600MHz

 

 

The Elevation Plot

 

 

The Elevation Plot 15m above ground

 

 

The Stunning SWR of this fantastic Antenna!

 

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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