Tag Archives: tower

Bidirectional switchable 40m wire yagi

I switched on the other evening and heard a very quiet DX caller on 7.142. It was YC0LOU from Indonesia and I could only pick up parts of his call. He called and called and had no takers. In fairness, he was extremely quiet but as the sun was gradually moving around the sky, he finally became audible and it was worth giving him a shout. 400w off my inverted V at 7m height got his attention but I needed a few blasts for him to get my call right. I put him on the cluster and he had a pile up.

Now, the point is, had I had more gain, I’d have not only heard him better, but he’d have heard me quicker too.

So I could add more height to my Inverted V but the difference between 7m and 10m isn’t actually that much at 5 degrees off the horizon – not even a db. Hardly worth writing home about.

40m-wire-yagi-drawingAnyway, this was the QSO that made me sit up and take stock of what I could do. I was seriously considering phased verticals for DX when I thought up the idea of having a switchable wire yagi. Either firing East or firing West.

Like me, you may already have an inverted V dipole up for 40m, all you need to is build another one about a quarterwave in front – or behind your existing dipole but out of a single wire. You don’t need to feed this with coax, it’s a parasitic element, like a 2 element yagi.

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How to build a tilt-over 60 foot antenna mast from scaffolding poles

This job is not for the feint-hearted. You will need a natural tendency for engineering, be accurate and be comfortable with knots. However, there’s no reason that most small teams of keen amateur radio operators can’t build this as a project for field day use.

Let me explain how I built the one shown in the pictures, then I’ll cover the learnings with you later along with my own do’s and don’ts.   Continue reading

Tower Update

DSC_3207Last night, we finally fitted the rotator housing and G450 Yaesu Rotator to the tower and tested it out with a small VHF ZL Special which we’ll use for VHF NFD in July (being at 1,000 feet means that we might be able to get away without high-gain antenna arrays, time will tell).

Barry (M0DGQ) is working on designs for a hinged rotator cage which means we will be able to use a 20 foot aluminium pole at ground level. Maybe next year..?

Anyway, we can now claim the record for putting up a 35 foot antenna: 20 seconds with a hydraulic switch :)


Mobile Lighting Generator Mast

My_VT-1_at_half_height.jpgA 10k generator and a lighting tower; the ultimate toy for a radio amateur. You get a generator, a hydraulic 10m tower and big, big lights – all in one package. It’s heavy but with a braked trailer and the right vehicle, it’s breeze.

Picture shows tower at about half-height and Barry has kindly offered to make a rotator housing for the very top of the unit which we’ll sort out this winter.

It’s easy to climb on top to make adjustments (mandatory at a field day with rotator housing fitting etc) and only 20 seconds to “wind” the tower up. Fair dinkum, it’s not a 100 foot tower but horses for courses, a great little easy-to-use package.

We should be operational for next Spring (2008) where we can enjoy some lazy days out in the Cotswold Hills on VHF – as well as HF Field Day (which was the initial reason for getting it!).

Pretty, eh?