Wednesday, December 26, 2012

Servicing the Cobweb Antenna

Finally I've got round to begin the service of the home-brew Cobweb. Taking it down from the mast wasn’t as bad as I thought, I decided to do it now as the weather forecast is not good with high winds expected over the next few days, so while there was a break in the weather I zipped up the ladder and began the removal process.

 Once down the initial inspection was that it didn’t look too bad considering it’s been up on the mast for nearly two years and been subject to some pretty bad weather conditions. A bit of rust here and there on the metal tubes that hold the wooden poles, but perhaps through luck or my building capabilities it has managed to withstand all that has been thrown at it! 

  The wooden poles and the box are covered in mildew and slightly bowed, but still sound, the cables are fairly loose which I suspect is the main reason my SWR has been out, especially on 20 meters which at the last reading was 2.5. Interestingly I thought the box would have been pretty rusty inside but surprisingly looks very clean apart from a good ½ “ of water slopping inside, first thought was hmm, I forgot to drill any draining plugs!

 The wooden poles are going to be replaced with fibreglass, I managed to find some ex army surplus which should do the job nicely but I will have to wait as I’ve only just ordered them so it will take a few days to arrive. Since the main box is in such good condition I will do little except give the outside a good scrub and more importantly drill a couple of draining holes. 

The silicon grease has done its job and kept the contacts all clean and rust free, I'm amazed there is no rust on the copper wire or the steel screws. Originally I bought a Cobweb (back in the 90s) for the grand sum of £160 and when I sold it I remember inspecting the box and seeing how badly rusted everything was, so I was expecting the home-brew to be the same, just goes to show what a bit of silicone will do to protect.

Over the next few days I will tighten the cables and recheck the SWR and if needs be replace any that are suspect, luckily I have some spare cable that I got last summer from Maplins, (our version of Radio Shack). 

Looking inside the box it is a remarkable simple system that is very easy to build and yet gives great results. This is easily the best antenna I've ever built and quite honestly if I can build one anyone can. If you want further information look at the Cobweb Revealed website or alternatively please ask and I'll be happy to help where I can (but I warn you now I don't understand the theory, hi hi). I will include as many picture as I can during the service process so you can see just how easy it is put together.

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