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A Long 5 element LFA Yagi for 50MHz with a 4.9mtr boom

Revised February 2010 V1.3

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 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. However, this version is not a model with optimum suppression which would see a reduction in forward gain of 1dB. If you suffer with very bad noise on 50MHz 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:

 

The 4.9m lonf 5el LFA at JA2DDN



The 4.9m 5el 50MHz LFA at EI7BA - above this is a 8el 2m LFA Yagi

 


 

Performance

Gain: 11.01dBi @ 50.150MHz

F/B: 19.37dB @ 50.150MHz

Peak Gain: 11.04dBi

Peak F/B: 19.98dB

SWR: Below 1.1.1 from 50MHz to 50.600MHz

Construction

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

Email for different tube sizes, for 12mm loop reduce to 1.238mm

Antenna Dimensions for 10/13mm tube

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.484                                             10mm or 3/8 inch

DE1                      .319                          1.239    (1.240 for 12mm Tube)        13mm or 1/2 inch

DE2                      .864                          1.239    (1.240 for 12mm Tube)         13mm or 1/2 inch

D1                       1.543                         1.390                                             10mm or 3/8 inch

D2                       3.055                         1.342                                             10mm or 3/8 inch

D3                       4.865                         1.299                                             10mm or 3/8 inch

 

Antenna Dimensions for all elements in 12mm with 10mm loop ends

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.4855                                            12mm

DE1                      .288                          1.2455              feedpoint                 12mm

DE2                      .823                          1.2455                                            12mm

D1                       1.471                         1.3835                                            12mm

D2                       3.014                         1.3285                                            12mm

D3                       4.900                         1.2775                                            12mm

 

The ends of DE1 and DE2 are connected together with 10mm or 3/8 inch tube. 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 the swr graph is correct and confirmed within nec4 and through building this antenna.

 

 

 

 

 

 

Any questions, please ask!

 

Justin G0KSC

 
 
 
 

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