Thursday, June 23, 2011

Further Fun with Antennas - Part 2

So now I had three antennas the W3DZZ, the Mystery and the Carolina all working reasonably well but unfortunately my garden had taken on the look of a large antenna farm with wires criss crossing all over the place and members of my family were none too pleased. I must admit looking at all these wires did make me think that there must be an easier way.

Back when I first started amateur radio the best antenna I ever owned was the Cobwebb, a five band omni directional dipole which at 8’ square could fit in a small sized garden with little trouble, a simple compact layout that worked extremely well. But I had made a promise not to buy another commercially made antenna and in any case the price of £300 was out of the question.

However the thought did cross my mind that now I had some experience I could possibly have a go or at least an attempt at building one and I reasoned that other hams must have tried and succeeded. 

Once more I trawled through the internet and found a number of hams who had successfully built their own Cobwebs. Reading up on their experiences and by coming across the detailed plans of the original Cobwebb I thought it was worth a go.

The next day after making the decision to build I promptly went down to Maplins to buy the necessary kit, I ended up spending approximately £45 mostly on speaker cable and the junction box together with the connection wires. 

Within 3 days I had completed the connection box and by a stroke of luck also found an Australian ham on “YouTube” who had recently completed the antenna, (any potential builders out there it's well worth a view). Through following his video and reading the design plans it all seemed to come together pretty smoothly. My only problem was finding fibreglass poles to support the speaker wire and in the end I popped down to my local hardware store and located some lightweight wooden poles and after a good soaking in wood treatment they seemed to be fine for the job.

Overall the Cobweb took me ten days to build but I was pleasantly surprised by the outcome. The antenna looked just like an original and seemed to weigh about the same. I mounted it on a 5ft pole to do some testing, fearing the worst that it would be a nightmare to trim, it was by all accounts one of the easiest parts of the job. The Cobweb is now mounted 35’ on my aluminium scaffold pole that has been moved so that it is attached against one of the walls to my house.

The finished product

The Windom and the W3DZZ have been taken down and stored away. The Mystery antenna is still up in my silver birch as an inverted vee and this covers the 80 and 40m bands when required. 

Since progressing with my CW I have also built a simple 30 meter inverted vee as I have found that neither the cobweb nor the Mystery covers that band particularly well but otherwise everything now seems to work fine. I  have now had good contacts from the US and Australia (atmospheric conditions permitting). 

The Cobweb is slightly above house height but no one has complained except for one neighbour who asked me what sort of TV reception did I get with that?
The next plan is to build myself a tilt over mast so that i don't try to break my back everytime I want to do adjustments, watch this space!

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