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3el 1.9mtr Boom LFA

A short 3 element LFA Yagi for 50MHz with a 1.94M boom

Revised 1st January 2010 V1.0

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 is a great stacker stack at 4.7 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.

 

The 3el LFA for 50MHz at AD6D

 

AB5EB's version of the antenna for IOTA

 

 

The 3el G0KSC LFA Yagi at VK2GOM

'The SWR hardly shows on the meter... probably about 1.1:1 across the part of interest (50.000 - 50.300)...' VK2GOM

 

The 3el 6M LFA built by Chris, M5LRO - Pawsey stub and thru-boom mounting also, well done Chris!

 

2E0ZMX made his 3el 6m LFA ready for E season 2010

 

 

Construction ideas from K5DIY

 

 

Full view of the K5DIY 3el LFA

 

 

 

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

Performance

Gain: 8.47dBi @ 50.150MHz

F/B: 30.37dB @ 50.150MHz

Peak Gain: 8.58dBi

Peak F/B: 30.7dB

SWR: Below 1.3.1 from 50MHz to 50.500MHz

Construction

Download the EZNEC filesHERE

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                              1.485                                             3/8 inch

DE1                      .416                          1.221                                             1/2 inch (feedpoint in this element)

DE2                      .947                          1.221                                             1/2 inch

D1                       1.940                         1.326                                             3/8 inch

 

Metric tubing:

 

Reflector                0                              1.484                                            10mm

DE1                      .416                          1.218                                             12mm (feedpoint in this element)

DE2                      .947                          1.218                                             12mm

D1                       1.940                         1.325                                             10mm

 

 

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.

 

An excellent pattern with very good gain for a 1.9M boom

 

The elevation pattern is nice and clean too

 

Not many antennas this small have this good an SWR curve, less than 1.3:1 for over 500KHz

 

 

 

Any questions, please ask!

 

Justin G0KSC

 
 
 
 

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