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2 short  4 element LFA Yagis for 50MHz with a 3.5M 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 commercial gain exists, express permission of G0KSC must be sought.

There are 2 versions of this antenna, scroll down the whole page to see all data for both antennas. Both have dimensions in Metric and Imperial tubing.

If you suffer with noise from living in the city, this is another low-noise antenna from G0KSC

This antenna is a great stacker Email me for more details

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 3.5m long 4el 50MHz LFA at G4SPD

 

4el 50MHz LFA at AD5A in Texas USA, complete with the G0KSC Antenna Balun fitted above the boom

 

 

The 4el LFA at XE2K. Note the G0KSC Antenna Balun on top. Details can be found here

 

 

The 4el 6M LFA at IG9/I2ADN

 

First is the wideband version which has a little less gain and F/B ratio. This antenna can be built with Metric or Imperial sized tubing:
 

Performance

Gain: 9.91dBi @ 50.150MHz

F/B: 19.01dB @ 50.150MHz

Peak Gain: 10.05dBi

Peak F/B: 26.25dB

SWR: Below 1.2.1 from 50MHz to 50.500MHz

Construction

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

Antenna Dimensions UK/USA

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.488                                             3/8 inch

DE1                      .346                          1.216                                             1/2 inch (feedpoint in this element)

DE2                      .926                          1.216                                             1/2 inch

D1                       1.902                         1.3605                                           3/8 inch

D2                       3.503                         1.292                                             3/8 inch

 

Metric tubing - European:

 

Reflector                0                             1.488                                             10mm

DE1                      .346                          1.213                                              12mm (feedpoint in this element)

DE2                      .926                          1.213                                              12mm

D1                       1.902                         1.3605                                            10mm

D2                       3.503                         1.292                                              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 3.5M boom

 

The elevation pattern is nice and clean too

 

Not many antennas this small have this good an SWR curve, less than 1.2:1 for over 500KHz

 

The next antenna is slightly longer than the above antenna, has a narrower bandwidth but good increases in gain and F/B ratio. European and UK/USA versions are listed.

 

Performance

Gain: 10.11dBi @ 50.150MHz

F/B: 21.86dB @ 50.150MHz

Peak Gain: 10.24dBi

Peak F/B: 26.86dB

SWR: Below 1.3.1 from 50MHz to 50.400MHz

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 UK/USA

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.493                                             3/8 inch

DE1                      .366                          1.224                                             1/2 inch (feedpoint in this element)

DE2                      .932                          1.224                                             1/2 inch

D1                       1.920                         1.3665                                           3/8 inch

D2                       3.572                         1.308                                             3/8 inch

 

Metric tubing - European:

 

Reflector                0                             1.493                                             10mm

DE1                      .366                          1.221                                              12mm (feedpoint in this element)

DE2                      .932                          1.221                                              12mm

D1                       1.920                         1.365                                              10mm

D2                       3.572                         1.308                                              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 slightly better gain and F/B than the wideband verison

 

The elevation pattern is nice and clean too

 

Bandwidth is reduced on this one although most hams are happy with 1.3:1 at band edges!

 

 

Any questions, please ask!

 

Justin G0KSC

 
 
 
 

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