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A Low-Noise 'Urban' 3 element LFA Yagi for 70MHz

Revised March 2010 V1.1

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.

EZNEC files for this antenna are on the download page.

If you suffer with noise from living in the city, this is an antenna for you.

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. Note there are no lobes striaght up and down in the Elevation plane.

Note: The loop feedpoint as per the photo, at the front of the loop nearest the reflector

Please read 'Making the LFA Loop which can be found HERE

 

3el 4m LFA built by M0KSJ

 

'Thought you might like to see a picture of my completed 3 ele LFA Yagi 
- I ran some more tests today using a temporary tripod mast at about 5m 
and was very impressed at being able to work G4ASR in Hereford plus
heard a very loud G4RFR in Dorset (didn't work as I went out into the
garden to manually adjust the beam heading and he'd vanished by the time
I got back).   Next step is to get it up on the rotatable mast on the
house at about 10m.'

Kevin, M0KSJ

 

Performance UK/US version

Gain: 8.66dBi @ 70.20MHz

F/B: 22.44dB @ 70.20MHz

SWR: bandwidth 500KHz 1.3.1

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

Antenna Dimensions

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.058                                             1/2 inch

DE1                      .347                          .886                 FEEDPOINT              1/2 inch

DE2                      .678                          .886                                               1/2 inch

D1                        1.388                       .9425                                              1/2 inch

 

Performance EU version

Gain: 8.63dBi @ 70.20MHz

F/B: 23.41dB @ 70.20MHz

SWR: bandwidth 500KHz 1.3.1

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

Antenna Dimensions

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.058                                            13mm

DE1                      .347                          .885                   FEEDPOINT           13mm

DE2                      .678                          .885                                              13mm

D1                        1.388                       .9425                                             13mm

Notes:

The loop ends are joined using 3/8 or 10mm tube.

Please read 'Making the LFA Loop which can be found HERE

 

Azimuth pattern of the UK/US version

 

Elevation plot of the UK/US version

 

SWR Plot of the UK/US version

As always, ask if you have any questions and I look forward to working you at field day!

Justin G0KSC

 
 
 
 

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