2 short 4 element LFA Yagis for 50MHz with a 3.5M boom
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
