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Premium commercial versions of this antenna at Innovantennas

 

A Low-Noise 'Urban' 10 element Plus2 LFA Yagi for 144MHz

Revised 17th January 2010 V1.3

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.

The 10el Plus2 144MHz LFA Built by ZS5LA

 

a 10el Plus2 2 Stack at ZS6JON

G0KSC's own 10el Plus2 LFA Yagi

 

 

 

4nec2 (with nec4 engine) Elevation plot of the 10el Plus2 LFA Yagi

 

The 11el 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

 

How the antenna will look when built (11el version shown)

 

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:                                   14.62dBi at 144.300MHz

Front to Back Ratio:                           26.43dB at 144.300MHz

Peak Gain:                                       14.64dBi

Peak F/B:                                          28.73dB

Bandwidth:                                       144-14.800MHz below 1.13:1

 

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

Element                     Spacing (m)     Half element Lengt            Element Notes

Plus2 Rear Reflectors         0               .511                         Above and below loop by 272mm 8mm tube

Reflector                                .251          .5175                       8mm Diameter tube or solid rod

DE1                                       .387            .432           (feedpoint)        10mm Tube

DE2                                       .550            .432                                      10mm Tube

D1                                         .806             .4765                      8mm Diameter tube or solid rod

D2                                         1.257           .4565                      8mm Diameter tube or solid rod

D3                                         1.642           .445                        8mm Diameter tube or solid rod

D4                                         2.172           .4495                     8mm Diameter tube or solid rod

D5                                         2.915           .444                       8mm Diameter tube or solid rod

D6                                         3.736           .436                       8mm Diameter tube or solid rod

D7                                         4.638           .424                       8mm Diameter tube or solid rod

D8                                         5.418           .424                       8mm Diameter tube or solid rod

 

Notes:

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

Feed point is the centre of DE1

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

As always, any questions please ask!

 

Justin G0KSC

Photos of my 10el LFA being built:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 
 
 

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