G0KSC 6 element 6m LFA Yagi - the airmail version for 3D2AG
Some years ago I had a pair of G0KSC 6 element 6m LFA Yagis (scroll down to the 'Stacking Version of this Antenna using UK/USA sized material') that were arranged in a 2-stack on a short tower next to my Ham shack. They performed very well, and their very clean radiation pattern resulted in excellent suppression of noise from unwanted directions.
Recently I built a single 6 element LFA that could be sent by airmail post. This provided an interesting challenge to build the antenna with no component longer than 1.5m to meet postal regulations. It also had to be fairly light weight to keep the postage cost down.
The boom was made from materials on hand: some new aluminium that was surplus from previous antenna builds, and some salvaged from the 'antenna graveyard' behind my shed! The 6.4m long tapered boom was made from various lengths of 35mm, 30mm and 25mm square box-section aluminium tube, with no part longer than 1.48m.
Fairly robust but light weight elements were made from short lengths of 1/2" dia aluminium center tubes with 3/8" dia tube element tips arranged to meet the postal criteria. Internal sleeves strengthened the stress points at the 1/2" to 3/8" taper transitions. The correct 'stepped taper' element lengths were determined with the 4NEC2 antenna simulation program, which provided the following output:
4NEC2 output of the modified G0KSC 6 element 6m LFA Yagi with tapered elements
The LFA was then built and tested here at 6 meters high:
The LFA driven element was fed via a 1:1 balun using a 'Grounded Coaxial Quarter Wave Line' with ferrite cores on the cable near the driven element feed point, following the DG7YBN 'symmetrising' concept:
The resulting SWR and Return Loss curves look very good. Here are the actual measured plots using a SARK110 antenna analyser with the LFA on test at 6m high:
Dismantled and packed up, ready for the post:
Photos of the antenna installed at its final location on an island in the Pacific Ocean ...
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