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 Low-Noise 'Urban' 8 element LFA Yagi for 144MHz

Revised 25th 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 (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 8el LFA at IV3MUR for EME

 

VE7XDT installing his bay of 4 x 8el 144MHz LFA Yagis

 

 

The completed VE7XDT Array - more photos of this array at the bottom of the page

 

'Your antennae are PERFECT!!! We calibrated my MFK 269 first. After that we tuned the 4 antennae - all came

with in 1/2mm accuracy in dimensions!!! There is 250KHz zone with SWR being 1.0:1 - amazing!!! Lionel (VE7BQH)

was impressed .'

- VE7XDT

 

The 8el LFA at IK8YSW with G0KSC Antenna Balun installed (boom top) pic taken at IARU 2010 contest 

 

'Hi Justin, here some pictures of my fresh 144 MHz 8 el LFA during IARU VHF reg1 contest, also a picture of swr meter...
The antenna receives very little noise, it's very interesting !!

Thanks for this nice designed antenna .

73 de Errico - IK8YSW'

 

 

 

IK8YSW shows his impressive SWR on the above antenna during the contest

 

 


Jose EA2FL installs his 8el 2M LFA on top of his tower


 

The 8el 2M LFA at EI7BA

 

IV3MUR with his 8el 2m LFA installed with elevation for EME. The reflector is just 50cms from ground!

 

One of IV3MURs EME QSOs with this single 8el LFA. Note the -17 signal strength!



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

Performance European Version                             UK/USA Version

Forward Gain:                                 13.29dBi at 144.100MHz                 13.32dBi at 144.100MHz

Front to Back Ratio:                        25.69dB at 144.100MHz                 25.76dBi at 144.100MHz

Peak Gain:                                        13.35dBi                                           13.36dBi

Peak F/B:                                           27.85dB                                           28.36dB

Bandwidth:                                       1MHz below 1.1:1                       1MHZ below 1.1:1

 

Build Dimensions for European Version -  12mm Loop sizing is 434mm per half - always adjust for best SWR

Note: Dimentions  are the same for both antennas, only the tube diameter changes

Element                             Spacing in metres Half element Length in metres            Element Notes

Reflector                                0                                                           .515                                               1/4 inch OR 6mm mm Diameter tube or solid rod

DE1                                       .127                                                      .436                                               1/2 inch OR 13mm Tube

DE2                                       .29                                                        .436                                               1/2 inch OR 13mm Tube

D1                                         .46                                                        .480   (.4805 for UK/USA Version) 1/4 inch OR 6mm Diameter tube or solid rod

D2                                         .846                                                      .467                                               1/4 inch OR 6mm Diameter tube or solid rod

D3                                        1.466                                                     .457                                               1/4 inch OR 6mm Diameter tube or solid rod

D4                                        2.187                                                     .447                                               1/4 inch OR 6mm Diameter tube or solid rod

D5                                        2.973                                                     .434                                               1/4 inch OR 6mm Diameter tube or solid rod

D6                                        3.729                                                     .42                                                 1/4 inch OR 6mm Diameter tube or solid rod

 

Notes:

DE1 and DE2 are joined at the ends by either 10mm tube (when 13mm main sections used) or3/8 inch tube (when 1/2 inch main sections are used).

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 8el 144MHz LFA Yagi

 

SWR Plot for the UK/USA version of the G0KSC 8el 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 236.2 Kelvin for this array which is lower than any other array of this boom length (VE7BQH G/T list, Google search). Not only this, G/T which is the figure of merit used to determine an antennas ability to receive signals is also better than any other antenna of this length (-3.72dB).

 

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 8 element LFA Yagis configured in a 4 Bay array 2.4 metres Vertically and 2.6 metres horizontally. Optimum spacing still to be defined

Download the EZNEC files for this antenna HERE

 

The VE7XDT EME Array pointed to the stars...

 

 

At the moon - The VE7XDT array ready for action

 

As always, any questions please ask!

 

Justin G0KSC

 
 
 
 

Google Translate