COBWEB,HF,1/2W,8-BD,6,10,12,15,17,20,30,40M,KW . MFJ Cobweb Antenna turns your space problem into a stack of QSL cards from far away places . Ideal HF Antenna. Efficient. Transmitter power gets converted to RF, not to heating the ground, coax, or matching network components. G3TPW CobWebb Antenna for the 14, 18, 21, 24 and 28 MHz Bands All the other small multi-band commercial antennas that are available are less than.
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Please note that the SWR is referenced to the coax connector on the balun box; in practice the SWR bandwidth will be better than that shown because of losses in the feedline. Add to Watch list Watching. Lay the two coaxes alongside one another and connect centre-to centre and braid-to-braid at each end. The overall diameter fits nicely inside the aluminium poles with a few turns of PVC tape either side of the fixing hole.
The height whilst on-test was 10ft, about 4ft under my dipole and the comparison test was quite favourable.
Add to Watch list. Amateur Radio G3TXQ – Cobweb Antenna During recent range testing of a hexbeam I needed a horizontally-polarised resonant antenna covering 20m thru 10m which cobqebb be assembled and disassembled quickly and easily. Contact the seller – opens in a new window or tab and request a postage method to your location.
Trim the four ends to form short pigtails. The following photos show the general idea: Subject to credit approval. At the other end of the assembly right side of the ‘photo connect the coaxes in series: It’s spam or has links There are copyright or trademark issues It’s offensive or has swear words It includes Atenna about the seller Something else Cancel.
Description Postage and payments. None Parcelforce Global Value. Add to basket. Please enter a number less than or equal to 2.
When terminated with a Seller assumes all responsibility for this listing. The dimensions shown on the plan below are all in mm.
A BRAND NEW COBWEB ANTENNA TWIN WIRE CUSTOM BUILT AND 20 METERS | eBay
Delivery times may vary, especially during peak periods and will depend on when your payment clears – opens in a new window or tab. The main part of the CobWeb is the mounting-plate that holds the crossover poles and boom arm. This design permits the CobWeb to be mounted at any height up a typical 1. Not in stockordered only on customer request, down payment required, delay at c. The turn radius is a very compact 6. The base plate as well as the tube supporting the balun is made from aluminium, the tubes carrying the dipoles are made from glass fibre.
The mounting consist of 2 aluminium plates 0. Seller information mcr However, the folded dipole approach to matching has some disadvantages: Equally the wind surface is rather small, allowing a max. 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 1: This allows single-wire elements to be used, which simplifies assembly and tuning.
Back in the summer ofI decided that I antennx to build a CobWeb. This means that you can move the position of them quite easily if you need to make changes. The cobweb antenna meets the requirement nicely – it comprises 5 parallel dipoles bent into a square shape and mounted on a support structure made of fibreglass poles.
Skip to main content. A lightweight aluminium mast is sufficient to carry the antenna. This amount is subject to change until you make payment. See other items More Good bit of kit. The Cobweb antenna is a antenna which is easy and fast to install for portable operations, designed cobwwbb G3TPW.
Ratings and reviews Write a review. Back to home page. The use of twin lead adds to the weight of the antenna A shorting link has to be placed at a position along the folded dipole, determined by the differential-mode velocity-factor of the cable. Learn more – opens in new window or tab. If the item comes direct from a manufacturer, it may be delivered in non-retail packaging, such as a plain or unprinted box or plastic bag. Sntenna list is full.
The dimensions shown next to each wire are the qntenna from the outer-end of the PVC tube. Fully assembled, soldered, boxed, sealed and with optional dipole wires which will need pruning for resonance.
Ideally, the shorting link position should be adjusted as part of the initial antenna tuning – something which is not easy to do. Why is this review inappropriate? Click on the photos on the right for enlarged pictures, and see the bottom of this page for more construction details. Mounting The mounting consist of 2 aluminium plates 0. Full IP67 with Scotchcast 40 inside the feedbox.
Please enter a valid postcode. The “scramble-wound” air-cored balun often installed within the terminal box may not atnenna much choking impedance unless the dimensions and winding antennna are carefully controlled The use of twin lead makes it a little more difficult to assemble and disassemble the antenna if, as I do, you prefer to store the wires separately The alternative arrangement I used cobebb to combine the impedance transformation and balun cbowebb into a 1: The ends of the dipole elements are connected to spacer cords approx 6″ long using the brass inserts from plastic connector blocks; this arrangement allows any slack to be taken up easily by releasing the srews and sliding the wires through the inserts.