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VK7HH LFA Build and performance

22 January, 2018 - Reading time: 6 minutes

Further to my previous posts on the "hybrid" LFA...


I managed to finish construction over the weekend and install it on my tower. At the same time I also decided to take down my 6m yagi to convert to an LFA design too. So how does it perform?

That evening I ran some tests with Peter 7PD on WSPR. There seemed to be some tropo enhancement as usually I cannot hear him from my location. Tests seemed to show the antenna was working quite well. I also tuned to a local beacon and noted signal strengths pointing in different directions. In this area we have a lot of mountain ranges so it's difficult to get an accurate reading due to reflections/refraction from the beacon.

The most impressive bit about this antenna though that I noticed straight away was the lower noise I had overall on 2m. You may recall in my previous post  I mentioned that in the ZL direction I had high levels of noise on 2m. Well, this antenna has certainly improved on that! Rough measurements on the old antenna indicated about 12dB of increased noise in Spectrum Lab when pointing at ZL as compared to a relatively quiet area. The noise level increase is now only 6dB over that same direction. In fact the noise now peaks between 30-60 degrees, which is perfect as there is nothing to beam at in that direction.

Below are some photos of the build. As detailed before, I just used three (all I could fit) ferrite cores of known impedance over the feedline and placed them as close to the feedpoint as possible. I then also slipped three further cores, around the bend of the coax underneath the boom. I also made a "ugly balun" of some sorts, 2.5 turns of coax... I also connected the centre of the driven element non-feed end to the boom using a small screw and some lugs.

Photos of build below.

Loop assembly with coax feed.

Close up of mounting method to boom/mast

Boom to centre of driven element. Note, another lug is present under the screw head to the right hand side of the photo, soldered to the centre screw lug.

Return loss come up pretty good.