Transmitter power gets converted to rf, not to heating the ground, coax, or matching network components. Cobwebb 2 building the antenna picture gallery of building cobwebb 2 back for my second attempt i followed the details as captured in a pdf file created by steve roberts m0sjr. Reading a lot of enthusiastic stories on the cobwebb antenna originally by stephen webb, hence the webb and considering its dimensions i thought it would make a good compromise for my situation. Hamshack sunday the vertical antenna and a qrp rig elecraft k1 duration. Here is my setup for connecting to the mfj 259b analyzer that i have. I do not think the pdf gives the element support dimensions very clearly. Cobwebb revealed a 27 pages pdf file revealing secrets of the cobwebb or cobweb multiband antenna with many pictures and assembling details.
The drawing below, is a basic sketch of the cobwebb design only 1 dipole shown what is a cobwebb antenna and what is its gain. However some of those really wet early snowstorms that caked the antenna really shifted the resonant frequency by over 500 khz on. I have found two different sizes for the twin cable elements, figure 8 42 strand 0. Mfj hf cobweb wire dipole antennas cover multiple bands and are suitable for many restricted space applications. See all condition definitions opens in a new window or tab ensure that the two chokes are aligned i. Researching the original g3tpw cobwebb antenna for the 14, 18, 21, 24 and 28 mhz band file shown attached above, and variations of it, i settled on generally following the design shown below in the sketch. This design used twin speaker wire as the elements. Cobwebb spider antenna shortwave antennadiy production information ham antenna gift antenna manual chinaglobalmall. After a few more weeks of not getting on the air i managed to man handle the portable hexbeam up to about 4 above ground level note. Over the years i have experimented with quite a few wire antennas at home increasingly to minimise.
The pdf shows the 17m element as 4400mm, i think this is a misprint, 4040 was intended. I built a portable version of a cobweb antenna, it is based on a design by stephen webb g3tpw and my adaptation of the idea is to make it so that it can be collapsed easily and when required reassembled. As the antenna dries out the normal tuning is restored. The support structure is constructed from fibreglass cobwebv, and the wires are held in place by threading them through a tiewrap loop which is itself tiewrapped to the tubing. The basic design is the similar to my portable version but. This file is an excellent source of information containing instructions and measurements for the cobwebb, click here to view the file. Researching the original g3tpw cobwebb antenna for the 14, 18, 21, 24 and 28 mhz band file shown attached above, and variations of it, i settled on generally following the design shown below in the. The actual field test, cobwebb antenna with the ft450 hf radio work well in blindspot, in addition to cobwebb antenna does not require the land to build a complex network system, set up. Over the past 15 or 20 years i have heard many good reports from users of the g3tpw cobwebb antenna. Here are my notes which should hopefully help anybody else heading down the same path. Any reuse or redistribution of the contents of this website are strictly forbidden without authorization from mfj enterprises.
There was not enough time to find a pattern like distance or antenna used by the other side. I have a 200 ohm carbon resistor across the leads where you connect the antenna wires, then connect the core and shield of the 50 ohm coax to their respective wires. The cobweb antenna meets the requirement nicely it comprises 5 parallel cobwrbb bent into a square shape and mounted on a support structure made of fibreglass poles. Amateur radio communication equipment we sell amateur radio antennas, rf fitting plugs coax cable,mobile and home base, micrphones cb an ham radio m0zim. A cobwebb homebrew build by dave 2e0ddhm0mbd loughton. About the cobwebb antenna the resource is currently listed in in 2 categories. Listed under the antennas cobwebb category that is about cobwebb antenna projects. Balun construction there are 2 ways to make a cobweb antenna. The speaker wire should ideally be 42 strand, available from any electrical wholesalers. Junction box kicad project for the cobwebb antenna. If you are looking at this after speaking to me, you know it works.
Describe your experience with the g3tpw cobwebb antenna for 14, 18, 21, 24 and 28 mhz bands and tell us why you give it the rating you did required. Hall the arrl antenna book the american radio relay league inc. Also, they are terminated into ring type crimp lugs, that are crimped and soldered. I have a 200 ohm carbon resistor across the leads where you.
A dipole or a cobweb has a gain of about 5db over a dipole in free space. You can buy a complete cobwebb antenna, which can be purchased on. I have a very small back garden and am limited with what type of antenna i can use. After the success of my first cobweb antenna i decided to build a rigid version for my home qth, the design this time is based on one by g3txq. The antenna complimented my lowband horizontal dipole nicely and gave me the most useful hf bands 2010m without needing an atu. A great document that can guide you in making your own. The cobweb antenna is a antenna which is easy and fast to install for portable operations, designed by g3tpw. Listed under the antennascobwebb category that is about cobwebb antenna projects. It is a very efficient horizontally polarised omnidirectional antenna for the 14, 18, 21, 24 and 28 mhz bands, with a gain of 7 db over an isotropic radiator 7dbi. They have fiberglass spreaders and wire elements find mfj hf cobweb wire dipole. This link is listed in our web site directory since thursday feb 28 2008, and till today the cobwebb antenna has been followed for a total of 4589 times. Cobwebb 2 antenna radio telecommunications engineering. 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. The cobwebb is a five band 14 to 28mhz compact array of dipoles, bent into a square, almost omnidirectional and with unity gain.
The main category is cobwebb antenna projects that is about cobwebb antenna projects. The cobweb is fully omnidirectional so no need for expensive. Cobweb is one of europes largest cloud solutions providers. Im in the process of building a homebrew cobwebb ariel. See all condition definitions opens in a new window or tab now wind 8 turns of this twin cable onto a ft toroid to form a 1.
All information, images, and documents on this website are the sole property of mfj enterprises, inc. You will need 2x mm lengths of rg or rg for w max which can be linked via a series of short lengths of heatshrink tubing. A checkup on my homebrew cobweb after the terrible storms recently, all seems well and still going strong after 3 years. Im in the final stages of putting a cobwebb antenna together id been umming and arring about putting a cobwebb together for some time. Classic amateur radio g3txq cobweb antenna kd6rf blog. It is a very efficient horizontally polarised omnidirectional antenna for. Note the spelling of cobwebb vs cobweb the original g3tpw. The cobweb antenna meets the requirement nicely it comprises 5 parallel dipoles bent into a square shape and mounted on a support structure.
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