Canvey Island, Essex, England Justin@g0ksc.co.uk
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Twin boom quad
144MHz LFA Yagis
144MHz LFA Yagis

Low Noise LFA Yagis designed by G0KSC free to build for personal use.

144MHz LFA Yagis
70cms LFA Yagis
70cms LFA Yagis
Twin-Boom G0KSC Quads
G0KSC Twin-Boom Quads
Twin-Boom G0KSC Quads
G0KSC Custom Dish feeds - Above installation @ HB9Q
Custom low-noise dish feeds
Custom low-noise dish feeds
G0KSC Custom Dish Feeds

Above installation @ HB9Q

G0KSC Custom Dish feeds - Above installation @ HB9Q
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A Low-Noise 'Urban' 21 element Plus2 LFA Yagi for 144MHz

 

Premium commercial versions of this antenna at Innovantennas

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 commercial gain exists, express permission of G0KSC must be sought.

The new LFA Plus2 range includes an additional 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 temperature 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. PLEASE do not alter dimensions, unless your software package uses NEC4 calculation engine, you will not see SWR correctly.

The look fo the 21el Plus2 when built

4nec2 (with nec4 engine) Elevation plot of the 21el Plus2 LFA Yagi

The 21el 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 
  • 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

Performance European Version

Forward Gain:                                   18.47dBi at 144.300MHz

Front to Back Ratio:                           34.48dB at 144.300MHz

Peak Gain:                                       18.47dBi

Peak F/B:                                          40.51dB

Bandwidth:                                       144-145MHz below 1.1:1

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

Element                             Spacing in metres Half element Length in metres            Element Notes

Plus2 Rear Reflectors                0                                                           .520                                                Above and below loop by 200mm

Reflector                                .455                                                       .518                                               8mm Diameter tube or solid rod

DE1                                       .592                                                      .441                                                 10mm Tube

DE2                                       .785                                                      .441                                                 10mm Tube

D1                                         0.999                                                    .480                                                8mm Diameter tube or solid rod

D2                                         1.472                                                    .4665                                              8mm Diameter tube or solid rod

D3                                         1.909                                                    .450                                                8mm Diameter tube or solid rod

D4                                         2.405                                                    .4525                                              8mm Diameter tube or solid rod

D5                                         3.108                                                    .450                                                8mm Diameter tube or solid rod

D6                                         3.916                                                    .444                                                8mm Diameter tube or solid rod

D7                                         4.779                                                    .4395                                              8mm Diameter tube or solid rod

D8                                         5.673                                                    .4355                                              8mm Diameter tube or solid rod

D9                                         6.577                                                    .4325                                              8mm Diameter tube or solid rod

D10                                       7.510                                                    .428                                                8mm Diameter tube or solid rod

D11                                       8.452                                                    .425                                                8mm Diameter tube or solid rod

D12                                       9.390                                                    .422                                                8mm Diameter tube or solid rod

D13                                       10.341                                                  .4175                                              8mm Diameter tube or solid rod

D14                                       11.300                                                  .4125                                              8mm Diameter tube or solid rod

D15                                       12.276                                                  .4065                                               8mm Diameter tube or solid rod

D16                                       13.230                                                  .402                                                8mm Diameter tube or solid rod

D17                                       14.229                                                  .3915                                               8mm Diameter tube or solid rod

D18                                       15.145                                                  .3865                                               8mm Diameter tube or solid rod

D19                                       16.062                                                  .4015                                              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

There is simply no other antenna of a similar size (7.72W/L) that comes close in Sky Temperature or G/T performance (VE7BQH List)

Stacking distances 5.35 High, 5.45 wide Below are the figures from Tant with the stacking set at 5.7m x 5.7m.

As always, any questions please ask!

Justin G0KSC