Cobwebb antenna

During recent range cobwebb antenna of a hexbeam I needed a horizontally-polarised resonant antenna covering 20m thru 10m which could be assembled and disassembled quickly and easily.

The Cobwebb is an antenna that has gained in popularity in recent years. The horizontally polarized omnidirectional antenna is suitable for the 10m, 12m, 15m, 17m and 20m band. All elements are fed through one single feed line. At only half wave length above the ground, it will outperform any vertical antenna. Measuring only 2.

Cobwebb antenna

JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser. In stock, shipped in 1 to 2 days. The Cobweb antenna operates on the five upper shortwave bands 20, 17, 15, 12 and 10m. The five folded dipoles are fed via a common balun, only one feed line is required. The arrangement of the elements to each other and the ground effect results in a small gain compared to a dipole. The antenna is designed for a power up to W. The usable SWR bandwidth covers a large part of the respective band. The SWR minimum can be shifted as needed by changing the length of the dipoles. The unfolding of the dipoles results in very compact dimensions of about x cm.

Bad weather stops play Yesterday I thought the HF bands seemed particularly quiet.

Read the PDF file. Maybe a Google will find it elsewhere. Cobwebb CB1. Before I finished my construction I looked at the web and found Steve's site. The PDF shows the 17m element as mm, I think this is a misprint, was intended.

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Cobwebb antenna

Without question, the most difficult part of building the cobwebb antenna is the metalwork, and if like me, your engineering skills could be better then a full kit of pre-drilled parts is available from Aerial Parts in Colchester for a reasonable price, this project was built using this very kit. Various articles with slightly differing designs can be found in plentiful supply online, the G3TXQ version of the cobwebb is the one my friend and I chose to construct — download the instructions. Some designs of the antenna require the use of twin core insulated wire for the elements, and when using this method, at a given length, the insulation has to be stripped and the cores shorted together to allow matching. Construction is fairly straightforward if following the instructions. The most complicated part of construction is the current balun, but is fully explained in the downloadable pdf mentioned above. Trim the four ends to form short pigtails. Lay the two coaxes alongside one another and connect centre-to centre and braid-to-braid at each end. Although not strictly necessary, I find it helps keep things neat if you slide a few narrow pieces of heat-shrink tubing over the coaxes to keep them together.

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It also allows me to work each earlier mentioned band entirely. Add to wishlist. At last, in June , I have found time to complete my CobWebb. It works well especially for European QRP work I use the WSPRNet low power beacon system to compare the antennas side by side over the course of several thousand "contacts", both transmitting and receiving. I suspect that some metalwork in the roof of my house is the cause. Measuring only 2. The N chassis socket has a sealed cable connector, wrapped with self amalgamating tape, insulating tape and then hot melt glue. Frequency range MHz. For several days before the winds subsided one was hanging on just one wire, threatening to spear anyone below.

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I have adjusted tuning by altering the amount of end folded back. Saturday morning I set to work and I did the full tuning with the MFJ which took an age as the G3TXQ definitely has much finer tuning points, it dips very quickly and the freq range is literally a few hundred kilohertz, a noticeable difference to the much wider freq of the G3TPW. I measured one, from the centre along each spreader , , , , mm. I've designed and made adjustable gizmos that employ small hose clamps that can be loosened and moved along the length of the spreader. I've tried to give as much information here as I can, but you'll notice I don't go through the actual precise build process, there are plenty of links within these posts or on the right hand side of the webpage that give the detailed measurements etc depending on what type of cobweb you wish to build. The tuner at the feedpoint of the Square Halo With some pieces of aluminum from my scrap metal collection, I made some brackets and mounted the tuner where normally the feedpoint would be mounted. Our experts are there to help you in word and deed - independent of the frequency range and radio application. You have now created a single transmission line with a Characteristic Impedance of 25 Ohms Now wind 8 turns of this twin cable onto a FT toroid to form a Choke. Many thanks in advance for your reply and I hope to start cobwebb between next fede days. The element ends are rather crudely held by cord and hot melt glue. This site uses cookies from Google to deliver its services and to analyze traffic. I will begin collecting the needed stuff in the coming days and keep you informed of the project's developments. The Haloweb uses folded dipoles with closed ends for increased bandwith.