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A Low-Noise 'Urban' 16 element ultra low-noise (close spaced) LFA Yagi for 144MHz

Revised 30th August 2009 V1.0

Additional rear-fed model with more gain, F/B and better G/T Sky Temp added April 2010 see below

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 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 the EU 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 on order to create new models for each (geographic) regions tubing requirements. UK and USA 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 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

Download the European version of this antenna in EZNEC format HERE

 

The 16el LFA at EA3AXV

 

'Hi Justin:

Hi have build your LFA 16el-144 design for mi QTH at 13m tower level.
I live in an area very noised for H.T. power lines, in the first test of
the LFA I thought the antenna was not working properly, the usual noise
was down, more than 10dB.
But now I can listen, via EME, stations that had never been able to copy.

I send a photos of antenna and screenshot of EME contact with CE0Y/df2kz
worked without elevation system  in middle of a big pile-up of European
stations.
Now i am very pleased with the performance and low noise of your LFA.

Thank you very much for your work and dedication.

In next thime i send photos of the LFA28-432 i have build for my radio-club.

Sorry for mi bad english.

73
Quim EA3AXV'

 

 

 

The Completed EME contact with CE0Y/DK2ZF with Quims 16el LFA. No elevation was needed

 


 

EA4LU has his 16el LFA below a 30el 70cms LFA. Maximum SWR on either antenna is 1.08:1


In order to show how clean the pattern is on this antenna, I have presented below first a 3D side shot of the antenna pattern followed by the Elevation plot then the Azimuth plot from 4NEC2 modelling program. These plots show much more clearly then EZNEC.

 

The 16el 144MHz LFA exhibits an incredible super-clean pattern

 

The 16el Elevation plot presented in the 4nec2 antenna modelling package. As with all LFA's plenty of rearward suppression without loss of forward gain.

 

The all important 'Super Clean' Azimuth pattern as presented within 4nec2 at 144.100MHz

 

In order to demonstrate pattern stablility within the LFA model, the above is the pattern as generated at 144.300MHz

 

The last example presents the same at 144.600MHz. Not there are still not unwanted forward lobes.

Download the European version of this antenna in EZNEC format HERE

 

Note: Performance figures given at 144.100MHz, the EME centre frequency

Performance European Version                             UK/USA Version

Forward Gain:                                   16.99dBi at 144.100MHz                   -

Front to Back Ratio:                         33.38dB at 144.100MHz                   -

Peak Gain:                                        16.99dBi                                           -

Peak F/B:                                        34.51dB                                           -

Bandwidth:                                     1MHz below 1.1:1                             -

Build Dimensions for European Version

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .5085                                               8mm Diameter tube or solid rod

DE1                                       .247                                                      .445                                                10mm Tube

DE2                                       .413                                                      .445                                                10mm Tube

D1                                         .611                                                      .481                                                8mm Diameter tube or solid rod

D2                                        1.074                                                      .468                                               8mm Diameter tube or solid rod

D3                                        1.551                                                     .4595                                               8mm Diameter tube or solid rod

D4                                        2.133                                                     .454                                                8mm Diameter tube or solid rod

D5                                        2.821                                                     .4505                                              8mm Diameter tube or solid rod

D6                                        3.579                                                     .445                                                8mm Diameter tube or solid rod

D7                                        4.42                                                      .4395                                               8mm Diameter tube or solid rod

D8                                        5.296                                                     .4345                                              8mm Diameter tube or solid rod

D9                                        6.189                                                     .429                                                8mm Diameter tube or solid rod

D10                                      7.131                                                     .4225                                              8mm Diameter tube or solid rod

D11                                      8.048                                                     .4155                                              8mm Diameter tube or solid rod

D12                                      9.021                                                     .4075                                              8mm Diameter tube or solid rod

D13                                      9.943                                                     .4045                                              8mm Diameter tube or solid rod

D14                                      10.799                                                    .405                                               8mm Diameter tube or solid rod

 

 

Notes:

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

Feed point is the centre of DE2

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

Download the European version of this antenna in EZNEC format HERE

 

SWR Plot for the European version of the G0KSC 16el 144MHz LFA Yagi as displayed in EZNEC Pro/4

 

The above plot is the SWR as presented in 4nec2 (with nec4.1 claculation engine installed).

 

Antenna Elevation Plot within EZNEC Pro/4

 

The amazing Azimuth Plot of this fantastic wide-band 16el 144MHz LFA

 

EME Notes

This antenna makes an excellent EME antenna When used with 2 or 4 stack versions, performance becomes second to none at this boom length. Below is the TanT output screen showing that sky temperature is 211.5 Kelvin for this array which is excellent for only 5.19W/L. Not only this, G/T which is the figure of merit used to determine an antennas ability to receive signals is better than any other antenna of this length (-0.33dB). As with all 2M LFA's listed on this site, there is no other antenna listed on the VE7BQH G/T table that has the same length (or shorter) Boom with the same or better G/T figure.

 

G/T and Sky Temperature are better than any other antenna of this boom length (5.19W/L), period.

 

4 x 16 element LFA Yagis configured in a 4 Bay array 4.4 metres Vertically and 4.5 metres horizontally. With more time, even better results can be achieved.

 

The incredible Azimuth pattern of the 4 x 16 LFA EU array. Find another array that looks this good.

 

Even in the elevation plane massive suppression of unwanted side, rear and upward lobes contribute to the exceptional low temperature of this antenna array.

Download the European version of this antenna in EZNEC format HERE


NEW!!! Rear-fed 16el LFA - Best performance to date!! For other element diameters, please mail me!


Performance European Version                             UK/USA Version

Forward Gain:                                   17.33dBi at 144.300MHz                   -

Front to Back Ratio:                         36.52dB at 144.300MHz                   -

Peak Gain:                                        17.45dBi                                           -

Peak F/B:                                        37.10dB                                           -

Bandwidth:                                     1MHz below 1.1:1                             -

4 antenna stack gain:                       23.44dBi

 

Build Dimensions for European Version

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .512                                                10mm Diameter tube or solid rod

DE1                                       .182                                                      .438               feedpoint                    13mm Tube (.437 12mm tube)

DE2                                       .345                                                      .438                                                13mm Tube (.437 12mm tube)

D1                                         .596                                                      .4755                                              10mm Diameter tube or solid rod

D2                                        1.005                                                      .4465                                             10mm Diameter tube or solid rod

D3                                        1.365                                                     .4525                                              10mm Diameter tube or solid rod

D4                                        2.011                                                     .4495                                              10mm Diameter tube or solid rod

D5                                        2.789                                                     .4435                                              10mm Diameter tube or solid rod

D6                                        3.629                                                     .438                                                10mm Diameter tube or solid rod

D7                                        4.501                                                     .4345                                              10mm Diameter tube or solid rod

D8                                        5.385                                                     .4305                                              10mm Diameter tube or solid rod

D9                                        6.285                                                     .4275                                              10mm Diameter tube or solid rod

D10                                      7.203                                                     .422                                                10mm Diameter tube or solid rod

D11                                      8.134                                                     .414                                                10mm Diameter tube or solid rod

D12                                      9.111                                                     .410                                                10mm Diameter tube or solid rod

D13                                      9.998                                                     .405                                                10mm Diameter tube or solid rod

D14                                      10.846                                                    .4135                                             10mm 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

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

Azimuth plot of the rear-fed LFA

 

Elivation plot of the rear-fed LFA

 

SWR plot for the rear-fed LFA

 

And finally the incredible Tant figures for this antenna (in 4 bay)


 

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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