A Low-Noise 'Urban' 19 element ultra low-noise (close spaced) LFA Yagi for 144MHz
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, or want the perfect quite EME single antenna or array, this is another low-noise example from G0KSC
This is a 19 element 144MHz LFA Yagi produced using 3/8 inch elements with a 1/2 inch loop section. Other sizes available upon request.
This LFA has been designed for maximum suppresion of side, rear and elevation lobes. The result is an ultra clean antenna which will be a stunning performer for 144MHz. The antenna is super wide-band too with an SWR of less than 1.1:1 over more than 1MHz. Uncharacteristically of a Yagi, the LFA maintains F/B over this wide bandwidth and more importantly maintains its pattern too, some example pattern plots are given below for 144.100MHz, 144.300MHz and 144.600MHz. One of the reasons for pattern stablility and bandwidth is the close spacing of the elements on this range of LFAs.
This antenna is particularly good for EME purposes due to the class leading low noise (Sky Temperature) and G/T figures mentioned above. See the bottom of this page for more information.This low-noise property also means less man made noise will be picked up by the antenna too.
I have started to model individual antennas on individual diameter elements in order to achieve the best all round results. Using the same element spacing and changing element diameter has not shown consistant results and therefore, I will spend more time in order to create new models for each (geographic) regions tubing requirements. EUROPEAN versions will follow shortly.
PLEASE NOTE:
- This antenna WILL NOT show the true SWR in any antenna modelling package unless you are using one which uses the latest NEC4.1 calculation engine. Do not confuse nec versions with EZNEC versions. Unless you have EZNEC pro/4 you are using nec2 NOT nec4
- There are two sets of measurements listed below. One uses imperial sizes, the other uses metirc sizes. Ensure you use the correct one for the material you have
- 'within one or two millimetres' Will not do! take the time to ensure you get the spacing ant element lengths as close as you possibly can to the measurements below to ensure good, solid performance
- Please read the 'how to make the LFA Loop' page
Performance UK/USA Version - 19 element LFA Yagi
Forward Gain: 18.09dBi at 144.100MHz
Front to Back Ratio: 32.05dB at 144.100MHz
Bandwidth: Better than 1MHz below 1.1:1 (143.7 - 144.7MHz)
Sky Temperature: 211.1Kelvin
G/T: -5.16dB
Stacking Information:
Vertical Stacking: 4.95m
Horizontal Stacking: 5.20m
4 x antenna Sky temp: 208.9K
4 x antenna G/T: +0.85dB
4 x antenna Gain: 24.05dBi
Build Dimensions for UK/US Version
Element Position (M) .5 element length in metres Element Notes
Reflector 0 .512 3/8 inch Diameter tube or solid rod
DE1 .183 .443 1/2 Tube (feedpoint)
DE2 .347 .443 1/2 Tube
D1 .580 .4775 3/8 inch Diameter tube or solid rod
D2 1.017 .4475 3/8 inch Diameter tube or solid rod
D3 1.349 .4525 3/8 inch Diameter tube or solid rod
D4 1.986 .4515 3/8 inch Diameter tube or solid rod
D5 2.772 .445 3/8 inch Diameter tube or solid rod
D6 3.622 .439 3/8 inch Diameter tube or solid rod
D7 4.504 .435 3/8 inch Diameter tube or solid rod
D8 5.404 .4315 3/8 inch Diameter tube or solid rod
D9 6.318 .4285 3/8 inch Diameter tube or solid rod
D10 7.240 .4255 3/8 inch Diameter tube or solid rod
D11 8.175 .4215 3/8 inch Diameter tube or solid rod
D12 9.125 .416 3/8 inch Diameter tube or solid rod
D13 10.080 .4105 3/8 inch Diameter tube or solid rod
D14 11.025 .404 3/8 inch Diameter tube or solid rod
D15 11.994 .3965 3/8 inch Diameter tube or solid rod
D16 12.971 .3875 3/8 inch Diameter tube or solid rod
D17 13.775 .4015 3/8 inch Diameter tube or solid rod
Notes:
DE1 and DE2 are joined at the ends by either 8mm tube bent to 'trombone' inside the 12mm tube. You can use 10mm tube also, Adjust loop for best SWR.
Feed point is the centre of DE1
Please read the 'how to make the LFA Loop' page
Build Dimensions for European Version
Element Spacing in metres - Half element Length in metres Element Notes
Reflector 0 .5115 10mm Diameter tube or solid rod
DE1 .182 .443 12mm Tube (feedpoint)
DE2 .346 .443 12mm Tube
D1 .585 .4775 10mm Diameter tube or solid rod
D2 1.018 .447 10mm Diameter tube or solid rod
D3 1.349 .452 10mm Diameter tube or solid rod
D4 1.987 .451 10mm Diameter tube or solid rod
D5 2.771 .4445 10mm Diameter tube or solid rod
D6 3.620 .4385 10mm Diameter tube or solid rod
D7 4.503 .4345 10mm Diameter tube or solid rod
D8 5.404 .431 10mm Diameter tube or solid rod
D9 6.319 .428 10mm Diameter tube or solid rod
D10 7.241 .425 10mm Diameter tube or solid rod
D11 8.174 .421 10mm Diameter tube or solid rod
D12 9.122 .4155 10mm Diameter tube or solid rod
D13 10.078 .410 10mm Diameter tube or solid rod
D14 11.023 .4035 10mm Diameter tube or solid rod
D15 11.992 .396 10mm Diameter tube or solid rod
D16 12.970 .387 10mm Diameter tube or solid rod
D17 13.776 .401 10mm Diameter tube or solid rod
Notes:
DE1 and DE2 are joined at the ends by either 8mm tube bent to 'trombone' inside the 12mm tube. You can use 10mm tube also, Adjust loop for best SWR
Feed point is the centre of DE1
The Azimuth Plot 144.100MHz
Azimuth plot 144.300MHz
Azimuth plot 144.600MHz
The Elevation Plot
The Elevation Plot 15m above ground
The Stunning SWR of this fantastic Antenna!
As always, any questions please ask!
Justin G0KSC