This is an 18 element 144MHz LFA Yagi produced using 3/8 inch elements with a 1/2 inch loop section. There is also a European version using 10mm and 12mm tube. 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.
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 here
A 17el LFA of EA3AXV who modified the loop size in order to use 8mm rod all the way through the antenna
Quim made an excellent job of the feed point
Did you really expect the SWR to look any different to this?
A 17el LFA installed at 9A9SF
'Hi Justin !
Yes ...
I put up the antenna and it works very good
I make the LFA from one piece of 6mm
swr is 1:1.1
antenna is 25m high
I DON'T MOVE ANY ELEMENT ...ALL DIMENSIONS AND DISTANCE ARE EXACTLY HOW YOU CALCULATE !'
Yes ...
I put up the antenna and it works very good
I make the LFA from one piece of 6mm
swr is 1:1.1
antenna is 25m high
I DON'T MOVE ANY ELEMENT ...ALL DIMENSIONS AND DISTANCE ARE EXACTLY HOW YOU CALCULATE !'
9A9SF
Performance UK/USA Version - 18 element LFA Yagi
Forward Gain: 17.81dBi at 144.300MHz
Front to Back Ratio: 31.75dB at 144.300MHz
Bandwidth: Better than 1MHz below 1.1:1
Sky Temperature: 213.1Kelvin
G/T: -5.48dB
Stacking Information:
Vertical Stacking: 4.95m
Horizontal Stacking: 5.20m
4 x antenna Sky temp: 210.1K
4 x antenna G/T: +0.60dB
4 x antenna Gain: 23.82dBi
Build Dimensions for UK/US Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 .510 3/8 inch Diameter tube or solid rod
DE1 .174 .436 1/2 Tube (feedpoint)
DE2 .338 .436 1/2 Tube
D1 .589 .475 3/8 inch Diameter tube or solid rod
D2 1.005 .447 3/8 inch Diameter tube or solid rod
D3 1.357 .453 3/8 inch Diameter tube or solid rod
D4 1.988 .4505 3/8 inch Diameter tube or solid rod
D5 2.768 .4435 3/8 inch Diameter tube or solid rod
D6 3.614 .438 3/8 inch Diameter tube or solid rod
D7 4.489 .4335 3/8 inch Diameter tube or solid rod
D8 5.385 .430 3/8 inch Diameter tube or solid rod
D9 6.294 .427 3/8 inch Diameter tube or solid rod
D10 7.221 .4235 3/8 inch Diameter tube or solid rod
D11 8.147 .419 3/8 inch Diameter tube or solid rod
D12 9.089 .415 3/8 inch Diameter tube or solid rod
D13 10.025 .406 3/8 inch Diameter tube or solid rod
D14 10.984 .399 3/8 inch Diameter tube or solid rod
D15 11.994 .392 3/8 inch Diameter tube or solid rod
D16 12.734 .4035 3/8 inch Diameter tube or solid rod
Notes:
DE1 and DE2 are joined at the ends by either 3/8 tube bent to 'trombone' inside the 1/2 inch tube. Adjust for best SWR.
Feed point is the centre of DE1
Please read the 'how to make the LFA Loop' page here
Build Dimensions for European Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 .5095 10mm Diameter tube or solid rod
DE1 .174 .444 12mm Tube (feedpoint)
DE2 .338 .444 12mm Tube
D1 .589 .475 10mm Diameter tube or solid rod
D2 1.005 .4465 10mm Diameter tube or solid rod
D3 1.357 .4525 10mm Diameter tube or solid rod
D4 1.988 .450 10mm Diameter tube or solid rod
D5 2.768 .443 10mm Diameter tube or solid rod
D6 3.614 .4375 10mm Diameter tube or solid rod
D7 4.489 .433 10mm Diameter tube or solid rod
D8 5.385 .4295 10mm Diameter tube or solid rod
D9 6.294 .4265 10mm Diameter tube or solid rod
D10 7.221 .423 10mm Diameter tube or solid rod
D11 8.147 .4185 10mm Diameter tube or solid rod
D12 9.089 .4145 10mm Diameter tube or solid rod
D13 10.025 .4055 10mm Diameter tube or solid rod
D14 10.984 .3985 10mm Diameter tube or solid rod
D15 11.994 .3915 10mm Diameter tube or solid rod
D16 12.734 .403 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
The Elevation Plot
The Elevation Plot 12m above ground
The Stunning SWR of this fantastic Antenna!
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