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14el 144MHz LN LFA

A Low-Noise 'Urban' 14 element ultra low-noise LFA Yagi for 144MHz

Revised 27th August 2009 V1.0

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 array,  this is another low-noise antenna from G0KSC

This antenna has been built and tested with a version of this one being marketed by Vine Antennas. Again, like the other 2M LFAs before it, this antenna has better allround performance than any other antenna of the same boom length, included within the VE7BQH G/T table.

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.

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 and UK/USA versions of this antenna in EZNEC format HERE


 

KF6A installed his 14el LFA for working EME

 

'Hi Justin,

Looks like the antenna is working FB. Even though the moon degradation was -3.8db I worked 7 stations last

night via EME, DK3WG, I2RV, I2FAK, DK2PH, DK3EE, K9MRI, and F6FHP before I ran out of space to turn the

antenna. I have very limited turning room and can only steer the antenna maybe +/-10deg Az because it is on a

temporary support, although I did elevate it. The wind was blowing 66kph last night so I had LOTS of horrible

power line noise. I had to wait for the moon to get some distance above the horizon so I could avoid the noise

so most, if not all of the stations, were worked at an elevation of more than 25deg and not much ground gain

would have been involved, with the best signals of -18db from DK3EE and I2FAK.

I'll probably try to work more EME tonight since I did pretty well last night.

This was done using the built-in preamp in my TE 1452G SS amp with ~350w.

When I build my 6m OWA yagi I might just try to do the same thing with it and try to work a little EME from my

roof tower. That would be neat.'

KF6A

 

And one day later I had this from Dan.... 

 

'I worked more EME tonight. The degradation was -4.6db and I worked HA6NQ, OH7PI, DL1DWI, DF2ZC, SM5DIC,

SP2OFW, DK5SO, DK3EE (again) and F8DO. A few guys were speaker copy too. I ran out of elevation toward the

end and the last couple of guys were worked with my reflector barely a foot off the ground, hi. The antenna is

officially broken in and declared a success. Thanks for the great design!'

 

Dan KF6A

 

One of KF6A's first EME QSOs. Note Degradation is at -3.8dB and still a best signal of -18dB is seen !!

 

 

Another KF6A QSO from the same (first) evening and still a best report of -18, excellent results for a single Yagi

 

 

2 x 14el LFA Yagis for 2M in use at F1USF/P

'HELLO JUSTIN, l just made a photo from my portable station , but it s not easy ,bad light conditions, and bad camera too , but for me it s was more important to compare the 14 ele to  my 2*16 same long boom and after a day of tests it seems to be the same reception to half S meter point , so it s a good  system  swr is right 1.05,  my 16  ele are a little beat noisy in a particular direction about 2 S meter point , like you can see the motorhome roof is about 1m of the lowest antenna and no particular effect with doing a 360 turn, l will try a second test when wx conditions will be better at 1500 asl certainly the next month with a longer mast but its not easy alone to install the system, tks for all l will try a six meter too as soon as possible , and try to send us a long 70cm too more than 38 ele if possible'

Fabrice, F1USF

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

 

The 14el Elevation plot presented in the 4nec2 antenna modelling package. At first glance, the pattern

does not look balanced. That is until you start to realise how much rearward suppresion is going on here.


 

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


Download the European and UK/USA versions 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:                                   16.54dBi at 144.100MHz                 16.54dBi at 144.100MHz

Front to Back Ratio:                         42.96dB at 144.100MHz                   40.33dBi at 144.100MHz

Peak Gain:                                        16.54dBi                                           16.54dBi

Peak F/B:                                        46.38dB                                           43.2dB

Bandwidth:                                     1.5MHz below 1.1:1                       1.3MHZ below 1.1:1

Build Dimensions for European Version - If you need 12mm Loop sizing mail me

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .5075                                               10mm Diameter tube or solid rod

DE1                                       .261                                                      .447                                                13mm Tube

DE2                                       .428                                                      .447                                                13mm Tube

D1                                         .611                                                      .479                                               10mm Diameter tube or solid rod

D2                                        1.062                                                      .4615                                            10mm Diameter tube or solid rod

D3                                        1.545                                                     .457                                               10mm Diameter tube or solid rod

D4                                        2.15                                                       .451                                              10mm Diameter tube or solid rod

D5                                        2.849                                                     .4455                                             10mm Diameter tube or solid rod

D6                                        3.624                                                     .4405                                             10mm Diameter tube or solid rod

D7                                        4.464                                                     .4365                                             10mm Diameter tube or solid rod

D8                                        5.338                                                     .4305                                             10mm Diameter tube or solid rod

D9                                        6.213                                                     .426                                              10mm Diameter tube or solid rod

D10                                      7.125                                                     .42                                                10mm Diameter tube or solid rod

D11                                      7.984                                                     .42                                                10mm Diameter tube or solid rod

D12                                      8.817                                                     .4035                                           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 DE2

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

Download the European and UK/USA versions of this antenna in EZNEC format HERE

 

SWR Plot for the European version of the G0KSC 14el 144MHz LFA Yagi

 

Build Dimensions for UK/USA Version

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .5085                                               3/8 inch Diameter tube or solid rod

DE1                                       .261                                                      .447                                                1/2 inch Tube

DE2                                       .428                                                      .447                                                1/2 inch Tube

D1                                         .613                                                      .4795                                               3/8 inch Diameter tube or solid rod

D2                                        1.062                                                      .4625                                              3/8 inch Diameter tube or solid rod

D3                                        1.545                                                      .458                                                3/8 inch Diameter tube or solid rod

D4                                        2.15                                                       .452                                                3/8 inch Diameter tube or solid rod

D5                                        2.849                                                     .4465                                              3/8 inch Diameter tube or solid rod

D6                                        3.624                                                     .4415                                              3/8 inch Diameter tube or solid rod

D7                                        4.464                                                     .4375                                              3/8 inch Diameter tube or solid rod

D8                                        5.338                                                     .4315                                              3/8 inch Diameter tube or solid rod

D9                                        6.213                                                     .427                                              3/8 inch Diameter tube or solid rod

D10                                      7.125                                                     .421                                               3/8 inch Diameter tube or solid rod

D11                                      7.984                                                     .421                                               3/8 inch Diameter tube or solid rod

D12                                      8.817                                                     .4045                                             3/8 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 DE2

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

Download the European and UK/USA versions of this antenna in EZNEC format HERE

 

SWR Plot for the UK/USA version of the G0KSC 14el 144MHz LFA Yagi

 

Antenna Elevation Plot

 

European version Azimuth Plot

 

UK/USA Elevation 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 217.7 Kelvin for this array which is excellent. 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 (-0.96dB). This is the shortest ever arrya to go below -1.0 G/T for this length ans the 4 bay spacing is not optimised yet!

 

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

 

4 x 14 element LFA Yagis configured in a 4 Bay array 4 metres Vertically and 4 metres horizontally. With more time, even better results can be achieved.

Download the European and UK/USA versions of this antenna in EZNEC format HERE

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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