A Low-Noise 'Urban' 5 element LFA Yagi for 144-146MHz
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
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)
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
As always, any questions please ask!
Justin G0KSC