A Low-Noise 'Urban' 16 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 16el 2m Plus2 LFA built by G0BSU - Fantastic job Roger.

The G0BSU 16el Plus2 before being raised for contest duty

UU4JDF built 2 16el Plus2's the second is still floor mounted!

One of the UU4JDF 16el Plus2s being prepared for field day 2010

The 16el PLus2 UU4JDF pair ready for tower installation

The look of the 16el Plus2 in software model

4nec2 (with nec4 engine) Elevation plot of the 16el Plus2 LFA Yagi

The 16el 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:                                   17.26dBi at 144.300MHz

Front to Back Ratio:                           35.62dB at 144.300MHz

Peak Gain:                                       17.27dBi

Peak F/B:                                          35.69dB

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                                                         .513                                                 above and below loop by 300mm

Reflector                                .367                                                     .515                                                8mm Diameter tube or solid rod

DE1                                        .597                                                     .449                                                 10mm Tube

DE2                                       .763                                                      .449                                                 10mm Tube

D1                                         .956                                                      .481                                                 8mm Diameter tube or solid rod

D2                                         1.461                                                    .464                                                  8mm Diameter tube or solid rod

D3                                         1.908                                                    .4515                                                8mm Diameter tube or solid rod

D4                                         2.405                                                    .450                                                  8mm Diameter tube or solid rod

D5                                         3.117                                                    .4485                                                8mm Diameter tube or solid rod

D6                                        3.927                                                     .443                                                  8mm Diameter tube or solid rod

D7                                        4.787                                                     .439                                                  8mm Diameter tube or solid rod

D8                                        5.673                                                     .435                                                  8mm Diameter tube or solid rod

D9                                        6.577                                                     .431                                                  8mm Diameter tube or solid rod

D10                                      7.493                                                     .4265                                                8mm Diameter tube or solid rod

D11                                      8.438                                                    .420                                                  8mm Diameter tube or solid rod

D12                                      9.357                                                    .4145                                                8mm Diameter tube or solid rod

D13                                      10.298                                                  .4105                                                8mm Diameter tube or solid rod

D14                                     11.140                                                   .4085                                                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

As always, any questions please ask!

Justin G0KSC

A 12 element LFA Yagi for 70MHz with a 15.587mtr boom

Note: If you do not see this antenna in an element diameter you would like, mail me.

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, this is another low-noise antenna from G0KSC

This antenna has been designed in order to minimise the upward and downward lobes typically seen the the EL plane on Yagi antennas. By doing this, a drastic reduction in pick up of unwanted noise in City locations is the result. The double bonus is the likelihood of reducing transmitted interference too. If you suffer with very bad noise on 70MHz and have room for an antenna of this size, Email me for details of the very high suppression version.

This antenna can be built with Metric or Imperial sized tubing:



2 x 7el 4m LFAs at G0VHF/P

Performance

15.86dBi @ 70.200MHz

F/B 29.37dB @ 70.200MHz

SWR: Below 1.1.1 from 70MHz to 70.700MHz

Construction

Antenna Dimensions for UK/USA sized tubing

Spacing                                Half Element Size  in Metres                Element Diameter

Reflector                0                              1.0555                                           3/8 inch or 10mm tube or rod

DE1                      .287                          .881  (.880 with 12mm tube)      1/2 inch or 12mm tube

DE2                      .683                          .881  (.880 with 12mm tube)      1/2 inch or 12mm  tube

D1                       1.216                          .9915                                           3/8 inch or 10mm tube or rod

D2                       2.315                         .964                                              3/8 inch or 10mm tube or rod

D3                       3.715                         .947                                              3/8 inch or 10mm tube or rod

D4                       5.327                         .9335                                            3/8 inch or 10mm  tube or rod

D5                       7.001                         .9215                                            3/8 inch or 10mm tube or rod

D6                       8.744                         .907                                              3/8 inch or 10mm tube or rod

D7                       10.511                       .895                                              3/8 inch or 10mm tube or rod

D8                       12.358                       .8845                                           3/8 inch or 10mm tube or rod

D9                       14.207                       .880                                              3/8 inch or 10mm tube or rod

D10                     15.587                      .888                                               3/8 inch or 10mm tube or rod

The ends of DE1 and DE2 are connected together with 3/8 inch or 10mm tube or rod. the Feed point is the centre of DE1.

NOTE:

SWR will not read as per the graph below if you use a package with mininec or nec2. DO NOT Get your version of EZNEC confused with nec versions. Unless you have EZNEC Pro/4 you do not havew nec4. The swr graph is correct and confirmed within nec4 and through building this antenna.

DE1 and DE2 will have to be cut shorter than the above measurements in order to allow for the radius on the loop ends. Always adjust loop for best SWR.

Feedpoint gap 6-10mm this gap is not critical.

Please send photos of this antenna if you build it.

Azimuth Plot of this super antenna

The much improved elevation plot

Elevation plot at 18m up

The SWR curve is virtually the same with both metric and imperial sized tubing

Any questions, please ask!