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' 17 element Plus2 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.

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.

The look fo the 17el Plus2 when built

4nec2 (with nec4 engine) Elevation plot of the 17el Plus2 LFA Yagi

The 17el 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:                                   17.55dBi at 144.300MHz

Front to Back Ratio:                           35.98dB at 144.300MHz

Peak Gain:                                       17.57dBi

Peak F/B:                                          36.29dB

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              -.398                                                       .514                                                 above and below loop by 300mm

Reflector                                0                                                           .515                                                 8mm Diameter tube or solid rod

DE1                                       .196                                                      .4505                                                 10mm Tube

DE2                                       .361                                                      .4505                                                 10mm Tube

D1                                         .556                                                      .480                                                 8mm Diameter tube or solid rod

D2                                         1.065                                                    .464                                                  8mm Diameter tube or solid rod

D3                                         1.509                                                    .4515                                                8mm Diameter tube or solid rod

D4                                         2.006                                                    .451                                                  8mm Diameter tube or solid rod

D5                                         2.712                                                    .448                                                 8mm Diameter tube or solid rod

D6                                        3.519                                                     .443                                                  8mm Diameter tube or solid rod

D7                                        4.384                                                     .438                                                  8mm Diameter tube or solid rod

D8                                        5.274                                                     .435                                                  8mm Diameter tube or solid rod

D9                                        6.181                                                    .4315                                                  8mm Diameter tube or solid rod

D10                                      7.095                                                     .427                                                  8mm Diameter tube or solid rod

D11                                      8.035                                                    .423                                                   8mm Diameter tube or solid rod

D12                                      8.954                                                    .418                                                   8mm Diameter tube or solid rod

D13                                      9.898                                                    .410                                                   8mm Diameter tube or solid rod

D14                                     10.849                                                   .406                                                   8mm Diameter tube or solid rod

D15                                     11.687                                                   .408                                                   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

Nothing else of this boom size comes close to the Plus 2 on Sky temperature of G/T performance Check the VE7BQH G/T List

As always, any questions please ask!

Justin G0KSC