6 METER LFA ANTENNA



I have always wanted to try EME on any band, but especially on 6 meters where I was trying to make 100 countries. A new type of yagi has been developed by G0KSC called the LFA or Loop Fed Array. This antenna is reported as being lower noise than conventional yagis and had a very low SWR for 500 KHz, so I started assembling parts. W6QUV offered to give me the 32 foot boom off an old antenna, so the hard part was done.

The element to boom clamps were made from some "Z" extrusion that was noched on the ends to allow hose clamps. Plastic insulators were made on the lathe and split to allow tightening on the .50 and .375 inch diameter elements. The reflector and all the directors were made of .375 inch aluminum tubing that were joined in the middle with a 6 inch piece of .25 tubing that was pop rivited in place. Standard 2 inch antenna clamps were used to attach to the boom.

The driven element is a horizontal loop attached at 2 points to the boom and fed at the rear position. The loop is made of .50 tubing with the 2 connections on the ends being made of .50 flat stock with .375 solid rod extending into the element ends. Six inches of tapped rod were used to allow for adjustment. This construction guarantees that the loop is symetrical and is easy to build. Trying to bend tubing in a nightmare and this construction is closer to the computer model.




When noise in the city became too much, we moved into the country to an old farm. The LFA was assembled on its military mast where it quickly made enough QSOs for DXCC on 6 meters. With more room I could now aim in all directions, but needed to get a little higher. Three sections of Rohn 25G was placed in a yard of concrete to make a 25 foot, free standing, tower. Azmuth was controlled with a Yaesu G-800 rotor.



The antenna has up to 60 degrees of elevation. The mast plate holds the actuator and the boom plate hangs on a pivot pin. Another arm operates an elevation pot.





The elevation pot is powered by 5 volts from a regulator fed from a 12 volt DC source. Problems came up when I turned the antenna to the West and found the balance of the antenna changed and the readings were off. Since I already had 12 VDC on the tower, I decided to mount an inexpensive closed circuit camera so I could sight down the boom. That worked great until I tried it during the day or when it was cloudy. I had a small protractor that could give me good readings, but you couldn't see it as it was parallel with the boom and the camera. I made a bracket what held a small mirror and put the assembly in front of the camera.






After the first rain storm, I added a plastic box with holes for the camera and view down the boom.



Now all I need to do is aim at the moon when it's visible or rely on the rotator for azmuth and the protractor for elevation. The shape in the middle of the rectangular view hole is the driven element bracket. The moon is centered above the bracket about 2 inches up. It all seems to be working and I now have a total of 117 countries on 6 meters. The low antenna also works very good on e-skip into Europe in the Summer.




Complete dimensions with conversion to inches is here.




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