A Low-Noise 'Urban' 8 element Dual Reflector LFA2 Yagi for 50MHz

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.

Revised 20th August 2009 V1.0

So, is this an 8 element antenna or a7 element antenna with 2 reflectors? I prefer the later as this sits on a typical 7 element boom. However, I will leave what you call it, up to you..

This antenna is for experianced builders only and therefore, no build information is detailed below. However, EZNEC files are available for download on the download page of this site: Download page

The difference between the LFA ad the LFA2 is within the parasitic elements. The Reflector and in some cases the First Director are bent towards the feeding loop. This helps increase pattern cleanliness and provide a super-flat SWR curve along with a worthwhile increase in Front to Back ratio.

Another first for me and the LFA is tapered elements. Some Hams wanted tapered designs due to difficulties in getting longer sizes of tubing delivered although I much prefer single peice elements.

This antenna has been designed with pattern cleanliness, bandwdith, SWR and Front to Back in mind. Anyone with Yagi Optimizer and 5 spare minutes can produce an antenna with a similar boom length to this one with similar gain. However, the art is being able to maintain gain while increasing F/B, Bandwidth, reducing SWR to an absolute minimum and reducing unwanted lobes which cause interference and receive unwanted noise.

One of the reasons for the dual reflectors on this one is to reduce Elevation lobes which is difficult to do with an antenna of this boom length/number of elements.

I have 2 versions of this antenna, one with metric and the other with imperial sized elements.

European metric and UK/USA imperial design files upon the download page.

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. This is especially the case when bent elements are used. Do not adjust anything, this antenna will be just fine when built!
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 and element lengths as close as you possibly can to the measurements below to ensure good, solid performance
This is a 50 Ohm Antenna, no matching arrangement is needed. A simple 1:1 or choke balun will be fine. see 'creating a Balun' here
Please read the 'how to make the LFA Loop' page here
Please do not alter segmentation or try to 'tune' the antenna unless you have nec4 or better. SWR will not read true within anything else
Note the First Director bends in opporsite directions for the European and UK/USA versions. This is correct.