A Low-Noise 'Urban' 13 element Plus2 LFA Yagi for 144MHz
Revised 22nd 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 13el PLus2 at SM0RCL
'I just thought that you would like to see my 13-ele LFA. I'm sorry that the text is in Swedish, but I guess that you can enjoy the pictures.
Regarding performance it's a joy. Worked LA2Z with 10W to around 25meters of RG-213 with NO PRE-AMP :) Received him with
excellent signal. So what can I say, really impressed as usual. So now I just need the preamp up the mast and some more pwr.
Not to mention the 24m mast and three more antennas :)
73 de Kai'
How the 13el Plus2 will look once completed
4nec2 (with nec4 engine) Elevation plot of the 13el Plus2 LFA Yagi
The 13el 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
- 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: 16.21dBi at 144.300MHz
Front to Back Ratio: 32.72dB at 144.300MHz
Peak Gain: 16.23dBi
Peak F/B: 32.72dB
Bandwidth: 144-145MHz below 1.16:1
Build Dimensions for European Version - mail me if you need 12 or 13mm tube driven loop sizing
Element Spacing in metres Half element Length in metres Element Notes
Plus2 Rear Reflectors 0 .507 above and below loop by 225mm 8mm tube
Reflector .313 .5125 8mm Diameter tube or solid rod
DE1 .494 .445 10mm Tube
DE2 .659 .445 10mm Tube
D1 .873 .4795 8mm Diameter tube or solid rod
D2 1.349 .463 8mm Diameter tube or solid rod
D3 1.793 .452 8mm Diameter tube or solid rod
D4 2.330 .4515 8mm Diameter tube or solid rod
D5 3.027 .448 8mm Diameter tube or solid rod
D6 3.834 .442 8mm Diameter tube or solid rod
D7 4.694 .437 8mm Diameter tube or solid rod
D8 5.565 .433 8mm Diameter tube or solid rod
D9 6.463 .427 8mm Diameter tube or solid rod
D10 7.373 .4155 8mm Diameter tube or solid rod
D11 8.179 .421 8mm Diameter tube or solid rod
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
This part is getting boring I know but stack and bay at 3.8 Vertically and 4.2 metres Horizontally for the best G/T figure for this boom length, period.
As always, any questions please ask!