COBWEBB ANTENNA PDF
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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During recent range testing of a hexbeam I needed a horizontally-polarised resonant antenna covering 20m thru 10m which could be assembled and disassembled quickly and easily. The only drawback with the G3TXQ single-wire version is having to make-up the 1: See all mcr has no other items for sale. Postage cost can’t be calculated. The wires are terminated in solder tags which fit over 4mm bolts screwed through the terminal box.
Learn More – opens in a new window or tab International postage and import charges paid to Pitney Bowes Inc. This item will be sent through the Global Shipping Programme and includes international tracking.
The alternative arrangement I used was to combine the impedance transformation and balun functions into 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.
Find out more about vobwebb rights as a buyer – opens in a new window or tab and exceptions – opens in a new window or tab. This allows single-wire elements to be used, which simplifies assembly and tuning.
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: You’re covered by the eBay Money Back Guarantee if you receive an item that is not as described in the listing.
Learn More – opens in a new window or tab Any international postage and import charges are paid in part to Pitney Bowes Inc.
MFJ Enterprises Inc.
Terms and conditions apply. Due to the square arrangement of the dipoles the overall size is very small, just by cm. Sign in for checkout Check out as guest.
Please allow additional time if international delivery is subject to customs processing. Lay the two coaxes alongside one another and connect centre-to centre and braid-to-braid at each end. Here’s a SWR plot measured at 25ft above ground. Some folk have had difficulty visualising the balun construction, so here are more details; click on the cobaebb for higher resolution photographs. 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 Add to Watch list.
CobWeb Aerial | M∅PZT
At the other end of the assembly right side of the ‘photo connect the coaxes in series: The “scramble-wound” air-cored balun often installed within the terminal box may not provide much choking impedance unless the dimensions and winding style 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 was to combine the impedance transformation and balun functions into a 1: It was a experiment into compact multi-band HF aerials for the higher bands and various solutions existed: See all condition definitions – opens in a new window or tab End 2 is the one you connect to the SO socket.
You simply wind a total of 8-turns: Delivery times may vary, especially during peak periods and will depend on when your payment clears – opens in a new window or tab. Learn more – opens in a new window or tab. Read more about the condition. Good bit of kit. Computer modelling of this arrangement shows that one result of bending the dipoles is that the antenna is close to being omnidirectional in azimuth, with a Free Space eccentricity of about 4dB; a less attractive result is that the feedpoint impedance drops to around 12 ohms at resonance.
This makes mine cm square. You have now created a single transmission line with a Characteristic Impedance of 25 Ohms. Most purchases from business sellers are protected by the Consumer Contract Regulations which give you the right to cancel the purchase within 14 days after the day you receive the item. Your country’s customs office can offer more details, or visit eBay’s page on international trade. Accepted, Eligibility for PayPal Credit is determined at checkout.
Add to basket. However, the folded dipole approach to matching has some disadvantages: Now repeat all of the above steps to form a second 1: The wire tension keeps the whole assembly in place; this arrangement allows the antenna to be assembled and broken down very quickly. See the seller’s listing for full details.
No additional import charges on delivery. These small sizes and the small packing size of 11 x 11 x cm makes this antenna well suitable for vacations, fielddays, SOTA and other portable activities.
Why is this review inappropriate? April 24, in: Get the item you ordered or your money back. Expect about KHz of 3: 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.
High Quality 5 bander CobWeb Antenna
Please enter up to 7 characters for antebna postcode. One common balun feeds five dipoles which are folded in a roughly square shape, only one feedline is required. We may receive commission if your application for credit is successful. Select a valid country. Back in the summer ofI decided that I wanted to build a CobWeb.