A Low-Noise 'Urban' 13 element LFA Yagi for 50MHz
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.
I am not sure too many of these will be built due to size but I guess I maybe surprised. This is the ultimate single Yagi for 50MHz. If you build one, I must come and work the DX with it!
Like the 9, 10, 11 and 12 element version before it, this antenna has been designed with light-weight in mind and optimum performance through single piece elements. It has all the common attributes of an LFA Yagi, Flat SWR, Excellent Gain, fantastic Front to Back ratio and suppressed unwanted lobes.
A True DX'ers antenna and at over 25 metres long, not for every ham in the neighbourhood! However, this antenna does have a massive .3dB advantage over the smaller 12 element version and at these levels of gain, that can make quite a difference.In addition, I have supressed further the lobes around the centre of the antenna in order to improve receive performance even more.
Both European and UK/USA versions are available. Build and construction details are below and EZNEC files are available for download on the download page.
The 13 element LFA Yagi for 50MHz. How it will look when completed
4nec2 (with nec4 engine) Elevation plot of the 13el 50MHz LFA
13el 50MHz Azimuth plot from the 4nec2 antenna modelling package
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 calculation engine DO NOT confuse EZNEC with the NEC engine. EZNEC uses nec2 by default
- 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
- Please do not alter segmentation or try to 'tune' the antenna unless you have nec4 or better. SWR will not read true within anything else
Performance European Version UK/USA Version
Forward Gain: 16.15dBi at 50.150MHz 16.14dBi at 50.150MHz
Front to Back Ratio: 29.34dB at 50.150MHz 29.1dBi at 50.150MHz
Peak Gain: 16.18dBi 16.16dBi
Peak F/B: 37.25dB 36.96dB
Bandwidth: 500KHz below 1.1:1 500KHZ below 1.1:1
Build Dimensions for European Version - If you need 12mm Loop sizing mail me
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.484 10mm Diameter tube
DE1 .371 1.232 13mm Tube
DE2 .936 1.232 13mm Tube
D1 1.681 1.392 10mm Diameter tube or solid rod
D2 3.279 1.361 10mm Diameter tube or solid rod
D3 5.214 1.338 10mm Diameter tube or solid rod
D4 7.477 1.318 10mm Diameter tube or solid rod
D5 9.871 1.301 10mm Diameter tube or solid rod
D6 12.351 1.285 10mm Diameter tube or solid rod
D7 14.937 1.265 10mm Diameter tube or solid rod
D8 17.51 1.252 10mm Diameter tube or solid rod
D9 20.176 1.229 10mm Diameter tube or solid rod
D10 22.695 1.205 10mm Diameter tube or solid rod
D11 25.178 1.19 10mm Diameter tube or solid rod
Notes:
DE1 and DE2 are joined at the ends by 10mm tube
Feed point is the centre of DE1
SWR Plot for the European version of the G0KSC 13el 50MHz LFA Yagi
Build Dimensions for UK/USA Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.485 3/8 inch Diameter tube or solid rod
DE1 .371 1.233 1/2 inch Tube
DE2 .936 1.233 1/2 inch Tube
D1 1.681 1.393 3/8 inch Diameter tube or solid rod
D2 3.272 1.362 3/8 inch Diameter tube or solid rod
D3 5.214 1.339 3/8 inch Diameter tube or solid rod
D4 7.477 1.319 3/8 inch Diameter tube or solid rod
D5 9.871 1.302 3/8 inch Diameter tube or solid rod
D6 12.351 1.286 3/8 inch Diameter tube or solid rod
D7 14.937 1.266 3/8 inch Diameter tube or solid rod
D8 17.51 1.253 3/8 inch Diameter tube or solid rod
D9 20.176 1.23 3/8 inch Diameter tube or solid rod
D10 22.695 1.206 3/8 inch Diameter tube or solid rod
D11 25.178 1.191 3/8 inch Diameter tube or solid rod
Notes:
DE1 and DE2 are joined at the ends by 3/8 tube
Feed point is the centre of DE1
SWR Plot for the UK/USA version of the G0KSC 13el 50MHz LFA Yagi
Antenna Elevation Plot
European version Azimuth Plot
UK/USA Elevation Plot
As always, any questions please ask!
Justin G0KSC