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A Low-Noise 'Urban' 6 element LFA Yagi for 144MHz

Revised 26th 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, this is another low-noise antenna from G0KSC

This one is really nice and compact, has good badnwdith (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 x 6el LFA 'on contest' at G0VHF September 2010

'The LFAs performed well showing a stronger rx and much wider beamwidth than the 2 x 12el M2 on the other tower...'

 

 

Note: performance figures centred on 144.100MHz the centre EME frequency

Performance European Version                                   UK/USA Version

Forward Gain:                                 11.97dBi at 144.100MHz                 11.96dBi at 144.100MHz

Front to Back Ratio:                        23.79dB at 144.100MHz                 23.89dBi at 144.100MHz

Peak Gain:                                        11.96dBi                                           11.96dBi

Peak F/B:                                           24.2dB                                            24.26dB

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

 

Build Dimensions for European Version - If you need 12mm Loop sizing mail me

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .517                                               10mm Diameter tube or solid rod

DE1                                       .108                                                      .439                                              13mm Tube

DE2                                       .283                                                      .439                                              13mm Tube

D1                                         .468                                                      .479                                              10mm Diameter tube or solid rod

D2                                         .943                                                      .459                                              10mm Diameter tube or solid rod

D3                                        1.629                                                     .441                                              10mm Diameter tube or solid rod

D4                                        2.349                                                     .429                                              10mm Diameter tube or solid rod

 

 

Notes:

DE1 and DE2 are joined at the ends by either 10mm 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

SWR Plot for the European version of the G0KSC 6el 144MHz LFA Yagi

 

Build Dimensions for UK/USA Version

 

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                            .517                                               3/8 Inch Diameter tube or solid rod

DE1                                       .108                                                      .438                                              1/2 inch Tube

DE2                                       .283                                                      .438                                              1/2 inch Tube

D1                                         .468                                                      .479                                              3/8 inch Diameter tube or solid rod

D2                                         .943                                                      .459                                              3/8 inch Diameter tube or solid rod

D3                                        1.629                                                     .441                                              3/8 inch Diameter tube or solid rod

D4                                        2.349                                                     .429                                              3/8 inch Diameter tube or solid rod

 

 

Notes:

DE1 and DE2 are joined at the ends by either 10mm 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

SWR Plot for the European version of the G0KSC 6el 144MHz LFA Yagi

 

Antenna Elevation Plot

 

European version Azimuth Plot

 

UK/USA Azimuth Plot

 

EME Notes

This antenna makes an excellent EME antenna when configured in a 4 bay stack. Below is the TanT output screen showing that sky temperature is a super low 224.4 Kelvin.There is no other array this short on the VE7BQH list (apart form the G0KSC 7element!). However, the sky temperature is lower on this array than many of the longer arrays listed (VE7BQH G/T list, Google search).

 

There are no antennas as short as this on the VE7BQH G/T list. However, this array still outperforms longer arrays in all respects

 

4 x 6 element LFA Yagis configured in a 4 Bay array  and showing current distribution. 2 metres Vertically and 2.7 metres horizontally. Optimum spacing still to be defined

Download the EZNEC files for this antenna HERE

 

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

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