Google Translate

×

Message

EU e-Privacy Directive

This website uses cookies to manage authentication, navigation, and other functions. By using our website, you agree that we can place these types of cookies on your device.

View e-Privacy Directive Documents

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

Revised 5th September 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, 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)

Construction

Download the EZNEC files for this antenna HERE

For full details of how to make the LFA, read here: http://www.g0ksc.co.uk/making-the-lfa-loop.html

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

Construction

Download the EZNEC files for this antenna HERE

For full details of how to make the LFA, read here: http://www.g0ksc.co.uk/making-the-lfa-loop.html

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

Download the EZNEC files for this antenna HERE

 

Any questions, please ask!

 

Justin G0KSC

 
 
 
 

Google Translate