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12el Plus2 144MHz

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

 

Revised 23rd December 2009 V1.0

 

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.

 

The 12el Plus2 144MHz LFA installed at ON6NL

 

 

ON5GS who built the Plus2 for ON6NL stands proudly by his work.

 

 

'Hello Justin!

Thanks! It was a great QSO with UA3PTW (Via EME). His best signal was -21db and I got -29db.
The antenna used was a 12 el. G0KSC +2LFA made by Dirk, ON5GS.
Find attached some pictures we made during the antenna party last week Nov. 11
when Dirk, ON5GS and Leo, ON6LEO helped me to put the antenna in the mast.
You see Dirk on the picture, proud on his great job done. Next to the +2LFA on the
ground you see my 25 year old DL6WU who did a fine job until his last day.
The guy in the mast wearing a red jacket is Anton, ON6NL.
The first tests with the new antenna were very positive. We heard several 4 yagi stations from the
moon! The SWR is incredible! 1:1.0 from 144.000 to 144.750 and 1:1.1 for the rest of the band.
We checked it with 2 analysers!

QRG R Xj
144000 55 0
144250 56 0
144500 58 0
144750 55 3
145000 51 7
145250 51 6
145500 54 0
145750 55 6
146000 50 7

Today I worked  in MS SV2JL, who copied me through a local thunderstorm, and
YU1IO. After that I copied some nice signals from the moon and worked UA3PTW.
Rig here is a IC756Pro2+transverter+PA giving 130W into 40m Ecoflex cable and a masthead
SSB preamp. And now a 12el +2LFA on an  18 meter mast in total at 50 meter asl.

I think Dirk will be satisfied with the results and finish his 4 stack of this antenna.
Thanks for donating the design to the ham community! It is really appreciated.
If I can you help with more info or higher definition photos, let me know.

73, Anton, ON6NL'

 

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

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 (m) - Half element Length (m) -  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.

 

 

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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