A Low-Noise 'Urban' 15 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, 12, 13 and 14 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 30 metres long, not for every ham in the neighbourhood! However, this antenna does have a massive .3dB advantage over the smaller 14 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 15 element LFA Yagi for 50MHz. How it will look when completed
4nec2 (with nec4 engine) Elevation plot of the 15el 50MHz LFA
15el 50MHz Azimuth plot from the 4nec2 antenna modelling package
SWR as presented in the 4nec2 antenna modelling package using nec4.1 Double Precision calculation engine
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
Download both the European and UK/USA EZNEC files HERE
Performance European Version UK/USA Version
Forward Gain: 16.68dBi at 50.150MHz 16.7dBi at 50.150MHz
Front to Back Ratio: 34.60dB at 50.150MHz 34.48dBi at 50.150MHz
Peak Gain: 16.70dBi 16.73dBi
Peak F/B: 35.11dB 35.00dB
Bandwidth: 500KHz below 1.1:1 500KHZ below 1.1:1
Build Dimensions for UK/USA Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.484 3/8 Diameter tube or solid rod
DE1 .400 1.232 1/2 inch Tube
DE2 .965 1.232 1/2 inch Tube
D1 1.712 1.394 3/8 Diameter tube or solid rod
D2 3.316 1.363 3/8 Diameter tube or solid rod
D3 5.239 1.341 3/8 Diameter tube or solid rod
D4 7.489 1.322 3/8 Diameter tube or solid rod
D5 9.857 1.305 3/8 Diameter tube or solid rod
D6 12.339 1.289 3/8 Diameter tube or solid rod
D7 14.907 1.272 3/8 Diameter tube or solid rod
D8 17.497 1.257 3/8 Diameter tube or solid rod
D9 20.105 1.24 3/8 Diameter tube or solid rod
D10 22.717 1.213 3/8 Diameter tube or solid rod
D11 25.396 1.193 3/8 Diameter tube or solid rod
D12 28.014 1.172 3/8 Diameter tube or solid rod
D13 30.316 1.161 3/8 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 15el 50MHz LFA Yagi
Build Dimensions for European Version - mail me if you need 13mm tube driven loop sizing
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.483 10mm Diameter tube or solid rod
DE1 .400 1.229 12mm Tube
DE2 .965 1.229 12mm Tube
D1 1.712 1.393 10mm Diameter tube or solid rod
D2 3.316 1.362 10mm Diameter tube or solid rod
D3 5.239 1.34 10mm Diameter tube or solid rod
D4 7.489 1.321 10mm Diameter tube or solid rod
D5 9.857 1.304 10mm Diameter tube or solid rod
D6 12.339 1.288 10mm Diameter tube or solid rod
D7 14.907 1.271 10mm Diameter tube or solid rod
D8 17.497 1.256 10mm Diameter tube or solid rod
D9 20.105 1.239 10mm Diameter tube or solid rod
D10 22.717 1.212 10mm Diameter tube or solid rod
D11 25.396 1.192 10mm Diameter tube or solid rod
D12 28.014 1.171 10mm Diameter tube or solid rod
D13 30.316 1.160 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 UK/USA version of the G0KSC 15el 50MHz LFA Yagi
3D plot image of this fantastic 15el 50MHz antenna
Download both the European and UK/USA EZNEC files HERE
As always, any questions please ask!
Justin G0KSC