A Low-Noise 'Urban' 12 element Plus2 LFA Yagi for 144MHz

 Revised 23rd December 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 sort. 

The new LFA Plus2 range includes an addtional 2 reflectors which are used in order to maintain pattern stability throughout the 1MHz coverage (144-145MHz).

This is the ultimate in 2m VHF performance today, the new LFA Plus2 is the one to beat showing flat SWR, pattern stability throughout and better sky tepmerature and G/T figures than any other Yagi of the same boom length (VE7BQH list).

Currently these antennas are available in METRIC SIZES ONLY. Imperial will be launched at a later date.

As with ALL LFAs this antenna requires no matching, it has a 50 Ohm input impedance.

 

Download both the European and UK/USA EZNEC files HERE

 

4nec2 (with nec4 engine) Elevation plot of the 12el Plus2 LFA Yagi

 

 

The 12el Plus2 Azimuth plot from the 4nec2 antenna modelling package

 

SWR as presented in the 4nec2 antenna modelling package using nec4.1 Double Precision calculation engine

 

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 EZNEC with the NEC engine. EZNEC uses nec2 by default
• 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
• Please do not alter segmentation or try to 'tune' the antenna unless you have nec4 or better. SWR will not read true within anything else

Download both the European EZNEC files HERE

Performance                                   European Version                       

Forward Gain:                                   15.72dBi at 144.300MHz                

Front to Back Ratio:                           33.78dB at 144.300MHz              

Peak Gain:                                        15.73dBi                                        

Peak F/B:                                          38.44dB                                      

Bandwidth:                                       144-145MHz below 1.1:1                     

 

Build Dimensions for European Version - mail me if you need 12 or 13mm tube driven loop sizing

Element                             Spacing in metres                           Half element Length in metres            Element Notes

Plus2 Rear Reflectors                0                                               .508                                       above and below loop by 225mm 8mm tube

Reflector                                .207                                           .514                                       8mm Diameter tube or solid rod

DE1                                       .369                                          .442                                       10mm Tube

DE2                                       .534                                           .442                                      10mm Tube

D1                                         .765                                          .4795                                     8mm Diameter tube or solid rod

D2                                         1.237                                        .4635                                     8mm Diameter tube or solid rod

D3                                         1.668                                        .4515                                     8mm Diameter tube or solid rod

D4                                         2.177                                        .451                                       8mm Diameter tube or solid rod

D5                                         2.874                                        .4475                                     8mm Diameter tube or solid rod

D6                                         3.685                                        .4415                                     8mm Diameter tube or solid rod

D7                                         4.554                                        .4345                                     8mm Diameter tube or solid rod

D8                                         5.435                                        .428                                       8mm Diameter tube or solid rod

D9                                         6.359                                        .418                                       8mm Diameter tube or solid rod

D10                                       7.135                                        .4295                                     8mm Diameter tube or solid rod

 

 

Notes:

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

Feed point is the centre of DE2

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

Stack and bay at 3.75 Vertically and 3.95 metres  Horizontally for the best G/T figure for this boom length, period.

 

Download both the European EZNEC files HERE

As always, any questions please ask!

 

Justin G0KSC