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Written by G0KSC   

A 11 element LFA Yagi for 70MHz with a 13.87mtr boom

Revised 9th September 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 antenna has been designed in order to minimise the upward and downward lobes typically seen the the EL plane on Yagi antennas. By doing this, a drastic reduction in pick up of unwanted noise in City locations is the result. The double bonus is the likelihood of reducing transmitted interference too. If you suffer with very bad noise on 70MHz and have room for an antenna of this size, Email me for details of the very high suppression version.

This antenna can be built with Metric or Imperial sized tubing:




This is a 6 element 50MHz version of this antenna installed at G0KSC July 2009

Performance

Peak Gain: 15.45dBi @ 70.180MHz

Peak F/B:  29.65dB @ 70.270MHz

SWR: Below 1.1.1 from 70MHz to 70.500MHz

Construction

Download the EZNEC files for this antenna HERE

For full details of how to make the LFA, read here: http://www.g0ksc.co.uk/making-the-lfa-loop.html

Antenna Dimensions for UK/USA sized tubing

                         Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.057                                           3/8 inch or 10mm tube or rod

DE1                      .302                          .882      (.881 with 12mm tube)      1/2 inch or 12mm tube

DE2                      .699                          .882    (.881 with 12mm tube)        1/2 inch or 12mm  tube

D1                       1.230                          .994                                            3/8 inch or 10mm tube or rod

D2                       2.347                         .968                                            3/8 inch or 10mm tube or rod

D3                       3.725                         .952                                             3/8 inch or 10mm tube or rod

D4                       5.304                         .938                                             3/8 inch or 10mm  tube or rod

D5                       7.000                         .926                                              3/8 inch or 10mm tube or rod

D6                       8.704                         .914                                              3/8 inch or 10mm tube or rod

D7                       10.517                       .897                                              3/8 inch or 10mm tube or rod

D8                       12.386                       .879                                              3/8 inch or 10mm tube or rod

D9                       13.872                       .889                                              3/8 inch or 10mm tube or rod

The ends of DE1 and DE2 are connected together with 3/8 inch or 10mm tube or rod. the Feed point is the centre of DE1.

 

NOTE: SWR will not read as per the graph below if you use a package with mininec or nec2. DO NOT Get your version of EZNEC confused with nec versions. Unless you have EZNEC Pro/4 you do not havew nec4. The swr graph is correct and confirmed within nec4 and through building this antenna.

 

Pattern is identical when using metric or imperial tubing. This is the Elevation Plot

 

 Azimuth Plot of this super antenna

 

The SWR plot is virtually the same with either metirc or imperial sized tubing

 

Download the EZNEC files for this antenna HERE

 

Any questions, please ask!

 

Justin G0KSC

 
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Copyright © 2009 G0KSC - Simple to build, High Performance Yagi and Quad Antennas - Home of the LFA Yagi. All Rights Reserved.
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