A Low-Noise 'Urban' 8 element LFA Yagi for 144MHz

Revised 25th August 2009 V1.0 

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. 

If you suffer with noise from living in the city, this is another low-noise antenna from G0KSC

This one is really nice and compact, has good badnwdith (1MHz 1.1:1) and yet has maintained an excellent pattern at the same time. Stacked in 4, you would not be unhappy with this very low-noise LFA for EME working. This antenna will be particularly good for EME purposes due to it's very low noise (Sky Temperature) and excellent G/T figures. See the bottom of this page for more information.

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 your version of EZNEC with nec version. 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

 Download the EZNEC files for this antenna HERE

Jose EA2FL installs his 8el 2M LFA on top of his tower

Note: performance figures centred on 144.100MHz the centre EME frequency

Performance                               European Version                             UK/USA Version

Forward Gain:                                   13.29dBi at 144.100MHz                 13.32dBi at 144.100MHz

Front to Back Ratio:                           25.69dB at 144.100MHz                 25.76dBi at 144.100MHz

Peak Gain:                                         13.35dBi                                           13.36dBi

Peak F/B:                                           27.85dB                                           28.36dB

Bandwidth:                                       1MHz below 1.1:1                       1MHZ below 1.1:1

Build Dimensions for European Version - If you need 12mm Loop sizing mail me

Note: Dimentions  are the same for both antennas, only the tube diameter changes

Element                             Spacing in metres                                Half element Length in metres            Element Notes

Reflector                                0                                                           .515                                               1/4 inch OR 6mm mm Diameter tube or solid rod

DE1                                       .127                                                      .436                                               1/2 inch OR 13mm Tube

DE2                                       .29                                                        .436                                               1/2 inch OR 13mm Tube

D1                                         .46                                                        .480   (.4805 for UK/USA Version)      1/4 inch OR 6mm Diameter tube or solid rod

D2                                         .846                                                      .467                                               1/4 inch OR 6mm Diameter tube or solid rod

D3                                        1.466                                                     .457                                               1/4 inch OR 6mm Diameter tube or solid rod

D4                                        2.187                                                     .447                                               1/4 inch OR 6mm Diameter tube or solid rod

D5                                        2.973                                                     .434                                               1/4 inch OR 6mm Diameter tube or solid rod

D6                                        3.729                                                     .42                                                 1/4 inch OR 6mm Diameter tube or solid rod

Notes:

DE1 and DE2 are joined at the ends by either 10mm tube (when 13mm main sections used) or3/8 inch tube (when 1/2 inch main sections are used).

Feed point is the centre of DE1

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

 Download the EZNEC files for this antenna HERE

SWR Plot for the European version of the G0KSC 8el 144MHz LFA Yagi

SWR Plot for the UK/USA version of the G0KSC 8el 144MHz LFA Yagi

Antenna Elevation Plot

European version Azimuth Plot

UK/USA Azimuth Plot

EME Notes

This antenna makes an excellent EME antenna when configured in a 4 bay stack. Below is the TanT output screen showing that sky temperature is 236.2 Kelvin for this array which is lower than any other array of this boom length (VE7BQH G/T list, Google search). Not only this, G/T which is the figure of merit used to determine an antennas ability to receive signals is also better than any other antenna of this length (-3.72dB).

There are no antennas as short as this on the VE7BQH G/T list. However, this array still outperforms longer arrays in all respects

4 x 8 element LFA Yagis configured in a 4 Bay array 2.4 metres Vertically and 3.15 metres horizontally. Optimum spacing still to be defined

As always, any questions please ask!

Justin G0KSC