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A short 5 element LFA Yagi for 50MHz with a 4.1mtr boom

Revised 9th December 2009 V1.1

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 commercial 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 is a great stacker stack at 4.1 metres apart either horizontally, vertically or both. For more information on stacking this antenna, Email me.

 

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:

 

Installed at VK2ZQ


 

A 5el 4.1 mtr LFA installed at G8FJG

 

 

The 4.1m LFA installed at G3MWV


 

Performance

Gain: 10.41dBi @ 50.150MHz

F/B: 29.20dB @ 50.150MHz

Peak Gain: 10.41dBi

Peak F/B: 32.79dB

SWR: Below 1.1.1 from 50MHz to 50.700MHz

Construction

Download the EZNEC files HERE

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

Antenna Dimensions

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.486                                             10mm or 3/8 inch

DE1                      .311                          1.248    (1.245 for 12mm Tube)        13mm or 1/2 inch

DE2                      .867                          1.248    (1.245 for 12mm Tube)        13mm or 1/2 inch

D1                       1.283                         1.411                                             10mm or 3/8 inch

D2                       2.460                         1.360                                             10mm or 3/8 inch

D3                       4.141                         1.296                                             10mm or 3/8 inch

 

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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