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A Low-Noise 'Urban' 5 element LFA Yagi for 144-146MHz

Revised 7th 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 one is really nice and compact, has good bandwdith (over 1MHz 1.1:1) and yet has maintained an excellent pattern at the same time. Stacked in 4, you would not be unhappy with this very low-noise LFA for EME working. This antenna will be particularly good for EME purposes due to it's very low noise (Sky Temperature) and excellent G/T figures. See the bottom of this page for more information.

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 your version of EZNEC with nec version. 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

Download the EZNEC files for this antenna HERE

4 stacked 5el LFAs at HB9FAP

 

'hi Justin. Hope U r fine. I am now at the VHF QTH and have mounted your 4x5el yagis.

I have mounted also 2x13 CC so that I can compare the 2 antennas systems. I am very

positive surprised abt your antennas! They are at least so good as the 2x13CC and even

a bit better! The lobe is very nicely broad and clearly (of course) wider than the 2x13CC.

I think they will do a very good job on MS during the coming MS Sprint on thursday.'

Fabio HB9FAP

 

Note: performance figures centred on 144.300MHz the centre SSB frequency

Performance

Forward Gain:                   11.17dBi at 144.400MHz

Front to Back Ratio:          19.93dBi at 145.100MHz

Bandwidth:                                  1MHZ below 1.1:1 (2MHz 1.3:1)

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

Download the EZNEC files for this antenna HERE

Azimuth Plot of this wideband 5el 144MHz LFA

 

Elevation Plot

 

SWR Plot from 144MHz to 146MHz

 

Build Dimensions for UK/USA/European version Version

 

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .513                                              3/8 Inch or 10mm Diameter tube or solid rod

DE1                                       .122                                                      .433 (.432 on Euro sizes)                 1/2 inch or 12mm Tube

DE2                                       .299                                                      .433  (.432 on Euro sizes)                1/2 inch or 12mm Tube

D1                                         .558                                                      .4685                                              3/8 inch  or 10mm Diameter tube or solid rod

D2                                        1.125                                                     .446                                              3/8 inch or 10mm Diameter tube or solid rod

D3                                        1.789                                                     .426                                              3/8 inch or 10mm Diameter tube or solid rod

 

 

Notes:

DE1 and DE2 are joined at the ends by either 10mm or 3/8inch tube. Feed point is the centre of DE1

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

Download the EZNEC files for this antenna HERE

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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