A 7 element LFA Yagi for 70MHz with a 6.89mtr boom

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, this is another low-noise antenna from G0KSC

This antenna has been designed in order to minimise the upward and downward lobes typically seen the the EL plane on Yagi antennas. By doing this, a drastic reduction in pick up of unwanted noise in City locations is the result. The double bonus is the likelihood of reducing transmitted interference too. However, this version is not a model with optimum suppression which would see a reduction in forward gain of 1dB. If you suffer with very bad noise on 70MHz and have room for an antenna of this size, Email me for details of the very high suppression version.

This antenna can be built with Metric or Imperial sized tubing:

The 7el 4m LFA installed above a WOS LFA at PA7F

A 7el 70MHz LFA and a 6el (6.8m long) 50MHz LFA at PA2J

OK1DFC has a 7el 70MHz LFA installed



2 x '7LFA4HVY' versions of this 7el 4M LFA Yagi - It looks like this array won the first RSGB 4M contest in 2010 too!

SWR plot of the G0VHF 'HVY's' between 69.850MHz and 70.550MHz

2 x 7LFA4HVYs installed at G8HVY

The SWR of Graham's 2 LFAs - Something the LFA has become famous for

EI2GLB's 7el 4m LFA above a 6el 6m LFA

'on 6m I have worked 5 new ones this year A92,A7,SU,ST & JY and usuals in Carib and some NA as well
On 4m I worked the First EI-OH on the band as also worked a load of OZ's, But I am QRT on 4m now until I fix my 847'

Trevor EI2GLB

The 7LFA4HVY is a 1/2 inch diameter element version of this antenna designed for Graham, G8HVY. Data on this antenna can be found below.

Performance

Peak Gain: 13.26dBi @ 70.250MHz

Peak F/B: 30.95dB @ 70.00MHz

SWR: Below 1.1.1 from 69.9MHz to 70.600MHz

Vertical Stacking: 4.5m to 6m (6m best)

Antenna Dimensions for UK/USA sized tubing

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.058                                           3/8 inch or 10mm tube or rod

DE1                      .249                          .882                                            1/2 inch or 12mm tube

DE2                      .639                          .882                                            1/2 inch or 12mm  tube

D1                        1.206                        .989                                             3/8 inch or 10mm tube or rod

D2                       2.387                         .958                                             3/8 inch or 10mm tube or rod

D3                       3.851                         .942                                             3/8 inch or 10mm tube or rod

D4                       5.321                         .927                                             3/8 inch or 10mm  tube or rod

D5                       6.89                          .908                                              3/8 inch or 10mm tube or rod

The ends of DE1 and DE2 are connected together with 3/8 inch or 10mm tube or rod. the Feed point is the centre of DE1.

G8HVY version - 7LFA4HVY

Performance

Peak Gain: 13.29dBi @ 70.250MHz

Peak F/B: 26.28dB @ 70.00MHz

SWR: Below 1.1.1 from 69.9MHz to 70.600MHz

Antenna Dimensions for UK/USA sized tubing

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.057                                           1/2 inch or 12mm tube or rod

DE1                      .270                          .882                                             1/2 inch or 12mm tube

DE2                      .662                          .882                                             1/2 inch or 12mm  tube

D1                       1.229                        .982                                              1/2 inch or 12mm tube or rod

D2                       2.377                         .950                                             1/2 inch or 12mm tube or rod

D3                       3.860                         .930                                             1/2 inch or 12mm tube or rod

D4                       5.481                         .911                                             1/2 inch or 12mm  tube or rod

D5                       6.995                         .896                                              1/2 inch or 12mm tube or rod

The ends of DE1 and DE2 are connected together with 3/8 inch or 10mm tube or rod. the Feed point is the centre of DE1.

12 or 13mm tubes can be used if required

NOTE: SWR will not read as per the graph below if you use a package with mininec or nec2. DO NOT Get your version of EZNEC confused with nec versions. Unless you have EZNEC Pro/4 you do not havew nec4. The swr graph is correct and confirmed within nec4 and through building this antenna.

Pattern is identical when using metric or imperial tubing. This is the Elevation Plot

Azimuth Plot of this super antenna

SWR as presented in 4nec2 Antenna Modelling package (nec4.1 double precision engine installed)

SWR Plot when European/metric tubing (12mm/10mm) is used

SWR Plot when Imperial (1/2 inch, 3/8 inch) tubing is used

Any questions, please ask!

Justin G0KSC

A Low-Noise 'Urban' 14 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 and 13 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 13 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 14 element LFA Yagi for 50MHz. How it will look when completed

4nec2 (with nec4 engine) Elevation plot of the 14el 50MHz LFA

14el 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

Performance European Version                             UK/USA Version

Forward Gain:                                   16.44dBi at 50.150MHz                 16.43dBi at 50.150MHz

Front to Back Ratio:                           30.91dB at 50.150MHz                  31.16dBi  at 50.150MHz

Peak Gain:                                       16.46dBi                                           16.45dBi

Peak F/B:                                          34.6dB                                           35.53dB

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                                       .389                                                         1.231                                               1/2 inch Tube

DE2                                       .954                                                         1.231                                               1/2 inch Tube

D1                                         1.714                                                       1.394                                               3/8 Diameter tube or solid rod

D2                                         3.303                                                       1.363                                               3/8 Diameter tube or solid rod

D3                                         5.231                                                       1.341                                               3/8 Diameter tube or solid rod

D4                                         7.481                                                       1.322                                               3/8 Diameter tube or solid rod

D5                                         9.867                                                       1.305                                               3/8 Diameter tube or solid rod

D6                                         12.341                                                     1.289                                               3/8 Diameter tube or solid rod

D7                                         14.91                                                       1.272                                               3/8 Diameter tube or solid rod

D8                                         17.478                                                     1.257                                               3/8 Diameter tube or solid rod

D9                                         20.164                                                     1.24                                                 3/8 Diameter tube or solid rod

D10                                       22.761                                                     1.213                                               3/8 Diameter tube or solid rod

D11                                       25.178                                                     1.193                                               3/8 Diameter tube or solid rod

D12                                       27.755                                                     1.172                                               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 14el 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                                       .389                                                      1.229                                                12mm Tube

DE2                                       .954                                                      1.229                                                12mm Tube

D1                                         1.713                                                    1.394                                               10mm Diameter tube or solid rod

D2                                         3.303                                                    1.362                                               10mm Diameter tube or solid rod

D3                                         5.231                                                    1.34                                                 10mm Diameter tube or solid rod

D4                                         7.481                                                    1.321                                               10mm Diameter tube or solid rod

D5                                         9.867                                                    1.304                                               10mm Diameter tube or solid rod

D6                                        12.341                                                   1.288                                               10mm Diameter tube or solid rod

D7                                        14.91                                                     1.271                                               10mm Diameter tube or solid rod

D8                                        17.478                                                   1.256                                               10mm Diameter tube or solid rod

D9                                        20.164                                                   1.239                                               10mm Diameter tube or solid rod

D10                                      22.761                                                   1.212                                               10mm Diameter tube or solid rod

D11                                      25.355                                                   1.192                                               10mm Diameter tube or solid rod

D12                                      27.755                                                   1.171                                               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 14el 50MHz LFA Yagi

Antenna Elevation Plot in EZNEC Pro/4

European version Azimuth Plot in EZNEC Pro/4

As always, any questions please ask!

Justin G0KSC