A Low-Noise 'Urban' 3 element LFA Yagi for 70MHz
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.
EZNEC files for this antenna are on the download page.
If you suffer with noise from living in the city, this is an antenna for you.
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. Note there are no lobes striaght up and down in the Elevation plane.
Note: The loop feedpoint as per the photo, at the front of the loop nearest the reflector
3el 4m LFA built by M0KSJ
'Thought you might like to see a picture of my completed 3 ele LFA Yagi
- I ran some more tests today using a temporary tripod mast at about 5m
and was very impressed at being able to work G4ASR in Hereford plus
heard a very loud G4RFR in Dorset (didn't work as I went out into the
garden to manually adjust the beam heading and he'd vanished by the time
I got back). Next step is to get it up on the rotatable mast on the
house at about 10m.'
Kevin, M0KSJ
Performance UK/US version
Gain: 8.66dBi @ 70.20MHz
F/B: 22.44dB @ 70.20MHz
SWR: bandwidth 500KHz 1.3.1
Antenna Dimensions
Spacing Half Element Size in Metres Element Diameter
Reflector 0 1.058 1/2 inch
DE1 .347 .886 FEEDPOINT 1/2 inch
DE2 .678 .886 1/2 inch
D1 1.388 .9425 1/2 inch
Performance EU version
Gain: 8.63dBi @ 70.20MHz
F/B: 23.41dB @ 70.20MHz
SWR: bandwidth 500KHz 1.3.1
Antenna Dimensions
Spacing Half Element Size in Metres Element Diameter
Reflector 0 1.058 13mm
DE1 .347 .885 FEEDPOINT 13mm
DE2 .678 .885 13mm
D1 1.388 .9425 13mm
Notes:
The loop ends are joined using 3/8 or 10mm tube.
Azimuth pattern of the UK/US version
Elevation plot of the UK/US version
SWR Plot of the UK/US version
As always, ask if you have any questions and I look forward to working you at field day!
Justin G0KSC