A Low-Noise 'Urban' 20 element LFA Yagi for 432MHz Revised 31st January 2010 V1.1 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 sort. Firstly, do not be put off by the close frontal side lobes on these 70cms Yagis. Those who follow my work within DUBUS magazine know I have proven forward side lobes have little effect on G/T figures as long as they are kept close to the main lobe, it is the size of the rear 'bubble' and F/R ratio that makes the most impact. By allowing these side lobes and amount of 'controlled' space in the forward direction, I have been able to suppress the rear lobes to produce antennas with never-seen-before G/T and Sky temperature figures! Currently these antennas are available in IMPERIAL SIZES ONLY. Mail me if you need anything different. As with ALL LFAs this antenna requires no matching device, it has a 50 Ohm input impedance. PLEASE do not alter dimensions, unless your software package uses NEC4 calculation engine, you will not see SWR correctly. 
Azimuth Pattern 
Elevation Pattern 
Elevation plot 10M up. Note the 'tight' rear bubble and 1 degree take-off 
SWR 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 UK/USA Version Forward Gain: 18.52dBi at 432.200MHz Front to Back Ratio: 37.49dB at 432.200MHz Peak Gain: 18.52dBi Peak F/B: 38.31dB Bandwidth: 432-433MHz below 1.1:1 Build Dimensions for UK/USA Version -
Element Spacing in metres Half element Length in metres Element Notes Reflector 0 .1.68 6.35mm - 1/4 inch rod DE1 .087 .1495 12.7mm - 1/2inch tube DE2 .159 .1495 12.7mm - 1/2inch tube (feedpoint) D1 .217 .1565 6.35mm - 1/4 inch rod D2 .371 .150 6.35mm - 1/4 inch rod D3 .525 .146 6.35mm - 1/4 inch rod D4 .701 .145 6.35mm - 1/4 inch rod D5 .932 .144 6.35mm - 1/4 inch rod D6 1.196 .142 6.35mm - 1/4 inch rod D7 1.486 .140 6.35mm - 1/4 inch rod D8 1.783 .139 6.35mm - 1/4 inch rod D9 2.090 .138 6.35mm - 1/4 inch rod D10 2.398 .1375 6.35mm - 1/4 inch rod D11 2.705 .1365 6.35mm - 1/4 inch rod D12 3.013 .136 6.35mm - 1/4 inch rod D13 3.325 .1345 6.35mm - 1/4 inch rod D14 3.638 .1325 6.35mm - 1/4 inch rod D15 3.957 .1315 6.35mm - 1/4 inch rod D16 4.287 .129 6.35mm - 1/4 inch rod D17 4.575 .125 6.35mm - 1/4 inch rod D18 4.884 .1295 6.35mm - 1/4 inch rod Notes: DE1 and DE2 are joined at the ends by 9.525mm - 3/8inch tube Feed point is the centre of DE2 Please read the 'how to make the LFA Loop' page here
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20el 432MHz LFA Yagi
