A Low-Noise 'Urban' 10 element LFA Yagi for 50MHz

Revised 27th August 2009 V1.0

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 just don't want to hear stations behind or to the side of you try this, another low-noise antenna from G0KSC

Like the 9 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 more than 17 metres long, not for every ham in the neighbourhood! However, this antenna does have a massive .6dB advantage over the smaller 9 element version and at these levels of gain, that can make quite a difference.

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 10el 50MHz LFA at CT1HZE

 

The 10el 6m LFA at G0VHF/P 2010 for the RSGB 6M Trophy - Built by G0KSC

 

Download both the European and UK/USA EZNEC files HERE

 

The 10 element LFA Yagi for 50MHz. How it will look when completed

 

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
• 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:                15.11dBi at 50.150MHz                 15.1dBi at 50.150MHz

Front to Back Ratio:        30.25dB at 50.150MHz                 30.54dBi at 50.150MHz

Peak Gain:                     15.13dBi                                           15.12dBi

Peak F/B:                       32.75dB                                            32.87dB

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   Half element Length (m)     Element Notes

Reflector            0                              1.482        10mm Diameter tube or solid rod

DE1                  .385                          1.228        13mm Tube

DE2                  .945                          1.228        13mm Tube

D1                   1.792                        1.386         10mm Diameter tube or solid rod

D2                   3.45                          1.355        10mm Diameter tube or solid rod

D3                  5.459                        1.331          10mm Diameter tube or solid rod

D4                  7.768                        1.313          10mm Diameter tube or solid rod

D5                 10.173                      1.297           10mm Diameter tube or solid rod

D6                 12.611                      1.281           10mm Diameter tube or solid rod

D7                 15.129                      1.256           10mm Diameter tube or solid rod

D8                 17.332                      1.246           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

Please read the 'how to make the LFA Loop' page here

SWR Plot for the European version of the G0KSC 10el 50MHz LFA Yagi

Download both the European and UK/USA EZNEC files HERE

Build Dimensions for UK/USA Version

Element      Spacing  Half element Length (M)      Element Notes

Reflector         0                               1.483         3/8 inch Diameter tube or solid rod

DE1               .385                           1.228         1/2 inch Tube

DE2               .945                           1.228         1/2 inch Tube

D1                1.794                         1.387          3/8 inch Diameter tube or solid rod

D2                 3.45                          1.356          3/8 inch Diameter tube or solid rod

D3                 5.459                        1.332          3/8 inch Diameter tube or solid rod

D4                 7.768                        1.314          3/8 inch Diameter tube or solid rod

D5                10.173                       1.298          3/8 inch Diameter tube or solid rod

D6                12.611                       1.282          3/8 inch Diameter tube or solid rod

D7                15.129                       1.257          3/8 inch Diameter tube or solid rod

D8                17.332                       1.247          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

Please read the 'how to make the LFA Loop' page here

SWR Plot for the UK/USA version of the G0KSC 10el 50MHz LFA Yagi

 

Antenna Elevation Plot

 

European version Azimuth Plot

 

UK/USA Elevation Plot

 

As always, any questions please ask!

 

Justin G0KSC