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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MFJ Enterprises Inc.
Anteenna 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. Representative APR variable Quite acceptable for the average transceiver.
Mounting The mounting consist of 2 aluminium plates 0. After extensive testing, I have came cobwbeb the conclusion that there is little difference between using black or white PVC tube the Wickes brand, at least — Therefore, you can choose the best colour to suit your QTH.
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Learn more – opens in a new window or tab. The antenna is built for a maximum power of W.
cobwebh Make 2 of these and link them together via 2 cable-ties — The ends of both are then soldered in the following way: Good bit of kit. Expect about KHz of 3: The coax needs to have a characteristic impedance of 25 ohms – something which is not easily available; so each balun is actually wound with two 50 ohm coaxes which are connected in parallel at each end – inner to inner, braid to braid.
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Add to shopping cart. The alternative arrangement I used was to combine the impedance transformation and balun functions into a 1: People who viewed this item also viewed.
Feedback on mcr from others who bought this item. 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. Easy to set up works well X Previous image. One common balun feeds five dipoles which are folded in a roughly square shape, only one feedline is required. Mouse over to zoom – Click to enlarge.
A brand-new, unused, unopened and undamaged item in original retail packaging where packaging is applicable.
In stockshipped in 1 or two days. Typically, when forming a dipole into a square shape, the impedance presented drops to around 12ohms — Hence the use of a 1: 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. A drive-over base and some swaged poles make a nice setup for operating from the car.
A BRAND NEW COBWEB ANTENNA TWIN WIRE CUSTOM BUILT AND 20 METERS | eBay
Email to friends Share on Facebook – opens in a new window or tab Share on Twitter – opens in a new window or tab Share on Pinterest – opens in a new window or tab. After looking at the various examples online, I opted to re-engineer an existing design — Some of which used either plastic PVC conduit clamps or small U-bolts — I opted to use the rugged Stauff element clamps which are able to support the spreaders securely without damaging or stressing them. Ratings and cobwevb Write a review.
A dipole or a CobWeb has a gain of about 5dB over a dipole in free space.
Please note that the wire used was PVC insulated with an outside diameter of 2mm and a conductor diameter of 1mm; dimensions will vary slightly if you use different wire. The Cobweb antenna covers the five upper shortwave bands 20, 17, 15, 12 and 10m.
Alpha Antenna M Multiband Military 2. I chose black as most of my CobWeb would be sitting just about the roof-tiles. Depending upon your circumstances, you may find this aerial visually more appealing that a 5-band flat-top fan dipole. Watch list is full. Add to Watch list. Get an immediate offer. We believe in our product and hold ourselves to the highest standards. Learn More – opens in a new window or tab Any international postage and import charges are paid in part to Pitney Bowes Inc.
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: Lay the two coaxes alongside one another and connect centre-to centre and braid-to-braid at each end. The dimensions shown next to each wire are the distances from the outer-end of the PVC tube. This amount is subject to change until you make payment.
This means that you can move the position of them quite easily if you need to make changes. I have opted for the G3TXQ version in this case.
The following table lists the wire dimensions that were used each side of the feedpoint, the distance from the centre of the structure to the wire corner, the minimum VSWR, the 2: Please enter up to 7 characters cbowebb the postcode. Learn Cobqebb – opens in a new window or tab International postage and import charges paid to Pitney Bowes Inc.
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