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A 12 element LFA Yagi for 70MHz with a 15.587mtr boom

Revised July 2010 V1.2

Note: If you do not see this antenna in an element diameter you would like, mail me!


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 sought.

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:




2 x 7el 4m LFAs at G0VHF/P

Performance

15.86dBi @ 70.200MHz

F/B 29.37dB @ 70.200MHz

SWR: Below 1.1.1 from 70MHz to 70.700MHz

Construction

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                              1.0555                                           3/8 inch or 10mm tube or rod

DE1                      .287                          .881  (.880 with 12mm tube)      1/2 inch or 12mm tube

DE2                      .683                          .881  (.880 with 12mm tube)      1/2 inch or 12mm  tube

D1                       1.216                          .9915                                           3/8 inch or 10mm tube or rod

D2                       2.315                         .964                                              3/8 inch or 10mm tube or rod

D3                       3.715                         .947                                              3/8 inch or 10mm tube or rod

D4                       5.327                         .9335                                            3/8 inch or 10mm  tube or rod

D5                       7.001                         .9215                                            3/8 inch or 10mm tube or rod

D6                       8.744                         .907                                              3/8 inch or 10mm tube or rod

D7                       10.511                       .895                                              3/8 inch or 10mm tube or rod

D8                       12.358                       .8845                                           3/8 inch or 10mm tube or rod

D9                       14.207                       .880                                              3/8 inch or 10mm tube or rod

D10                     15.587                      .888                                               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.

DE1 and DE2 will have to be cut shorter than the above measurements in order to allow for the radius on the loop ends. Always adjust loop for best SWR.

Feedpoint gap 6-10mm this gap is not critical.

Please send photos of this antenna if you build it.

 

 

Azimuth Plot of this super antenna


 

The much improved elevation plot

 

 

Elevation plot at 18m up

 

 


The SWR curve is virtually the same with both metric and imperial sized tubing

 

 

Any questions, please ask!

 
 
 
 

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