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The CobWebb Antenna

I never know if its CobbWebb or CobWebb. Either way this is a great multiband antenna for HF ripe for homebrew

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A bit of background - The CobWebb antenna design by G3TPW is an omnidirectional 5 band antenna that covers 20m - 17m - 15m - 12m - 10m. There are 2 variants. The original uses twin wire and tapping points to create the folded dipole whilst the single wire, designed by G3TXQ  uses a 1:4 balun to raise the impedence from 12.5 Ohms to 50 Ohms.

The single wire is by far the easiest to make in terms of tuning. No need to muck about with tapping points and trial and error. The original information from G3TXQ gives you some further background reading.

Framework

You can make up the framework yourself but there are alternatives. Antenna parts of colchester produce a 'kit' that gives you the basic structure you need from which to build. You only need to get the spreaders, wire and balun.

Spreaders

20mm PVC conduit is good for indoors which you can get from any DIY store. If its going to go outside then you really need GRP. Try engineered composites. They advertise regularly in RadCom and are really helpful on the phone.. 

Balun

The balun isn't tricky to build. M0PZT will show you the way and also sell you one from his Ham Goodies store complete with a box if you want

Ancillary parts

Wires, boxes terminals etc can all be got from CPC. They have been a good supplier to me so happy to recommend them. 

Build

If you are going for the 2 wire then there are some older instructions here. A link to the original design and a pat on the back for good luck from me. 

If you are going to build the single wire version, then follow Charlie's instructions. They are what I used and work fine. No need to repeat them.

Tune

You are going to need an analyser of some sort. Either treat yourself to some Mighty Fine Junk or as I've done get something off eBay. Bear in mnd that indication is what you are after, rather that absolute accuracy. Once installed there will always be a small difference to when you are tuning at ground level. Be prepred to hoist and luff a few times.

One tip: start at 10m and work down. it seems to work better than going the other way.