A Low-Noise 'Urban' 9 element LFA Yagi for 144MHz

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, this is another low-noise antenna from G0KSC

This antenna has been built, tested and used at the RSGB Field Day (2 X Stack) , July 2009. South Portugal being the best result during that contest from thisi fantastic performer. As with all LFA's I publish now, this is a wide-band, low noise antenna and will not shift dramatically in wet weather or when placed near other antennas.

This antenna is particularly good for EME purposes due to it's class leading low noise (Sky Temperature) and G/T figures. See the bottom of this page for more information.

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 calculation engine
• 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

Built by GM3PMB

4 x 9el LFA for 144MHz at WA8HTO

Installed and built by GU8FBO

RSGB Field Day 2009. G0KDV using 2 x 9el LFA Yagis

G8FJGs 9el 144MHz LFA between a 28/50MHz G0KSC DualBand Yagi and a 22el LFA Yagi

4 x 9el 144MHz LFAs at G3MLO (all parts required purchased from this site !!)

The 9el LFA for 144Mhz iinstalled at DL4KUG

A close up shot of the G0KSC 1:1 'Antenna Balun' installed on the 9el LFA

The finished 4 x 9el Array at DL4KUG

There many versions of this antenna below in different element diameters, scroll down!:

Performance                                   European Version                             UK/USA Version

Forward Gain:                                   14.15dBi at 144.300MHz                 14.13dBi at 144.300MHz

Front to Back Ratio:                           24.41dB at 144.300MHz                 24.86dBi at 144.300MHz

Peak Gain:                                        14.2dBi                                           14.18dBi

Peak F/B:                                          26.32dB                                          26.99dB

Bandwidth:                                       1.4MHz below 1.1:1                       1.6MHZ below 1.1:1

Build Dimensions for European Version

Element        Spacing in metres       Half element Length            Element Notes

Reflector        0                                 .515                         5mm Diameter tube or solid rod

DE1             .138                              .435                         13mm Tube

DE2             .306                              .435                         13mm Tube

D1               .532                              .473                         5mm Diameter tube or solid rod

D2               .806                              .462                         5mm Diameter tube or solid rod

D3              1.34                               .463                         5mm Diameter tube or solid rod

D4              2.052                             .4565                        5mm Diameter tube or solid rod

D5              2.837                             .45                           5mm Diameter tube or solid rod

D6             3.659                              .44                           5mm Diameter tube or solid rod

D7             4.447                              .435                         5mm Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 10mm tube

Feed point is the centre of DE1

SWR Plot for the European version of the G0KSC 9el 144MHz LFA Yagi

Build Dimensions for UK/USA Version

Element    Spacing in metres -  Half element            Element Notes

Reflector       0                           .515                   3/16 inch Diameter tube or solid rod

DE1            .138                        .435                   1/2 inch Tube

DE2            .306                        .435                   1/2 inch Tube

D1             .533                        .4735                  3/16 inch Diameter tube or solid rod

D2             .808                        .462                    3/16 inch Diameter tube or solid rod

D3            1.34                         .463                    3/16 inch Diameter tube or solid rod

D4           2.052                        .4565                  3/16 inch Diameter tube or solid rod

D5           2.837                        .45                      3/16 inch Diameter tube or solid rod

D6           3.659                        .44                      3/16 inch Diameter tube or solid rod

D7          4.447                         .435                    3/16 inch Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 3/8 tube

Feed point is the centre of DE1

SWR Plot for the UK/USA version of the G0KSC 9el 144MHz LFA Yagi

Performance                                   European Version 4mm                           

Forward Gain:                                   13.73dBi at 144.300MHz               

Front to Back Ratio:                           27.84dB at 144.300MHz              

Peak Gain:                                        13.80dBi                                         

Peak F/B:                                          28.13dB                                    

Bandwidth:                                       1.4MHz below 1.1:1                

Build Dimensions for European Version with 4mm parasitic elements

Element  = Spacing  - Half element Length             Element Notes

Reflector          0             .5165                           4mm Diameter tube or solid rod

DE1               .110           .4365                          12mm Tube

DE2               .274           .4365                          12mm Tube

D1                 .495          .4795                           4mm Diameter tube or solid rod

D2                 .845          .4665                           4mm Diameter tube or solid rod

D3                 1.322         .463                            4mm Diameter tube or solid rod

D4                 1.981        .4565                           4mm Diameter tube or solid rod

D5                 2.762        .449                            4mm Diameter tube or solid rod

D6                 3.576        .435                            4mm Diameter tube or solid rod

D7                 4.366        .4185                          4mm Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 10mm or 8mm tube. Adjust loop on completion for best SWR.

Feed point is the centre of DE1

Performance                                   UK/USA Version all elements 1/2 inch                           

Forward Gain:                                   14.04dBi at 144.300MHz

Front to Back Ratio:                           27.78dB at 144.300MHz

Peak Gain:                                        14.06dBi

Peak F/B:                                          28.08dB

Bandwidth:                                       800KHz below 1.1:1

Element  - Spacing  - Half element Length in metres            Element Notes

Reflector        0           .5075                                   1/2 inch Diameter tube or solid rod

DE1             .207        .4345                                  1/2 inch Tube

DE2             .381        .4345                                  1/2 inch Tube

D1               .564        .4675                                  1/2 inch Diameter tube or solid rod

D2              .837          .452                                   1/2 inch Diameter tube or solid rod

D3             1.402         .4495                                  1/2 inch Diameter tube or solid rod

D4             2.125         .440                                    1/2 inch Diameter tube or solid rod

D5             2.902         .430                                    1/2 inch Diameter tube or solid rod

D6             3.747         .415                                    1/2 inch Diameter tube or solid rod

D7            4.508          .409                                    1/2 inch Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by  3/8 inch tube. Adjust loop on completion for best SWR.

Feed point is the centre of DE1

Antenna Elevation Plot

European version Azimuth Plot

UK/USA Azimuth Plot

EME Notes

This antenna makes an excellent EME antenna when configured in a 4 bay stack. Below is the TanT output screen showing that sky temperature is 236.2 Kelvin for this array which is lower than any other array of this boom length (VE7BQH G/T list, Google search). Not only this, G/T which is the figure of merit used to determine an antennas ability to receive signals is also better than any other antenna of this length (-3.72dB).

G/T and Sky Temperature are better than any other antenna of this boom length, period.

4 x 9 element LFA Yagis configured in a 4 Bay array 3 metres Vertically and 3.1 metres horizontally

As always, any questions please ask!

 

Justin G0KSC

A High-Gain 6 element LFA Yagi with a 7.3 metre Boom for 50MHz

_____

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 sort.

Note, this LFA is not suited for location where high suppression of noise is required due to the existence of lobe elevation plane lobes. Where the best in noise suppression is required, chose a shorter 6el or a small 7el.

This antenna has been designed with performance in mind and provides optimum performance for the 7.3 metre boom length. As with all of my second generation LFA's wide bandwidth has been modelled into the antenna to ensure maximum performance without matching losses.

The 7.3m long 6el at OZ6ABA

The 7.3m 6el LFA at LZ1DP

Built my 9A9T 2011

The G0KSC 6 mtr Antenna, the 7.3 mtr long 6el LFA - installed 28th July 2009

The 6el at SP3OCC installed 2010

The same antenna built by VK4DDC

The 6el 7.3M long 50MHz LFA of OE4VIE

The 7.3M long 6el 50MHz LFA as built by UK8OM

EI2GLB's 6el 7.3m 6m LFA with 7el 4m version on top

'on 6m I have worked 5 new ones this year A92,A7,SU,ST & JY and usuals in Carib and some NA as well
On 4m I worked the First EI-OH on the band as also worked a load of OZ's, But I am QRT on 4m now until I fix my 847'

Trevor EI2GLB

Performance Standard Loop                              16mm or 0.63 Inch Loop

Forward Gain:                                   12.32dBi at 50.150MHz                  12.33dBi at 50.150MHz

Front to Back Ratio:                           22.87dB at 50.150MHz                  23.17dBi at 50.150MHz

Peak Gain:                                        12.38dBi                                     12.4dBi

Peak F/B:                                          25.46dB                                     25.46dB

Build Dimensions using 1/2 inch or 13mm elements

Element                             Spacing in metres Half element Length in metres

Reflector                                0                                                               1.488

DE1                                       .333                                                          1.236

DE2                                       .889                                                          1.236 (1.234 with 5/8 inch or 16mm loop)

D1                                        1.66 (1.58 with 5/8 inch or 16mm loop)          1.377

D2                                        3.386                                                         1.34

D3                                        5.286                                                         1.324

D4                                        7.243                                                          1.281

Notes:

DE1 and DE2 are joined at the ends by either 3/8 inch or 10mm tube when 1/2 inch or 13mm DE1 and DE2 are used. these end sections should be 1/2 inch or 13mm when 5/8 inch or 16mm main loop sections are used. If in doubt, Email me!

Feed point is ALWAYS the centre of DE1

Build Dimensions using 12mm elements

Element                             Spacing in metres Half element Length in metres

Reflector                                0                                                               1.4865

DE1                                       .330                                                          1.235 (Loop ends 10mm)

DE2                                       .884                                                          1.235 (Loop Ends 10mm)

D1                                        1.653                                                         1.378

D2                                        3.385                                                         1.340

D3                                        5.320                                                         1.320

D4                                        7.299                                                          1.281

Notes:

DE1 and DE2 are joined at the ends by 10mm tube when 12mm DE1 and DE2 are used. If in doubt, Email me!

Feed point is ALWAYS the centre of DE1

Performance plot with 13mm or 1/2 inch elements

Plot with 16mm or 5/8 inch driven loop with all other elements 1/2 inch or 13mm ( see build info)

Antenna layout showing the feedpoint (red circle) at the back of the loop closest to the reflector

SWR with 1/2 inch elements

SWR with 13mm elements