My Cobweb (single-wire) Antenna Build by Tony Breathnach EI5EM

This clip illustrates my progress from start to finish building a homebrew single wire Cobweb antenna for the five amateur bands; 20m, 17m, 15m 12m and 10m. I took lots of photographs during the project and these illustrate in easy to follow steps the construction of the antenna with accompanying captions.

[@Radioexperimenter]

Congratulations Tony! very good work! A dream come true and with the satisfaction of building it by hand. 73 EA8DGA- Tenerife

[@EI5EM]

Thank you and I am glad you liked the video.

[@tixilx]

Nice video ... I found that slowing to 0.5 gave me time to read the excellent onscreen comments and digest the excellent photographs .. Thanks ☘️

[@EI5EM]

I'm glad you liked the video and thanks for feedback.

[@tixilx]

@@EI5EM Hi Tony…… Have been wondering how the cobweb has been treating you ? 73… Gerry

[@EI5EM]

@@tixilx It is performing brilliantly. It has so far survived everything that the weather has thrown at it.

[@tixilx]

@@EI5EM That’s good to hear Tony … I’m looking forward to getting mine into the air … at least I’ll be able to see how it works on Rx @ approx 25’ Ok to mount my 2m/70 cm vertical on top of the pole ?

[@tonyhwang3888]

Thank you for the video. I am one step closer building one myself. Hardware kits I ordered could be here any day now. Season's greetings from Western Canada. Tony, VE6CGX

[@EI5EM]

Greetings from Dublin Tony. Good luck with the build.

[@abrahamnorthhampton3327]

Such a nice project, and quite effective, it sounds like. 73!

[@EI5EM]

Thanks OM!

[@rick5078]

Nice build. I am looking to build a cobweb myself and would have been awesome if there was someone selling the hardware kits and balun materials closer to Ecuador. Will just have to start searching around locally for parts I guess.

[@derodster]

that's very impressive tony. My next project I think. 73 de rod ei7df

[@EI5EM]

Thanks Rod. I think I did a good instructional video with lots of photographs and details for others to follow. The video production may not be great though but I hope the content makes up for that.

[@EI5EM]

I have an upcoming article in Echo Ireland on the project.

[@sreekumarg]

For the elements length, which formula you followed ? Kindly share..

[@EI5EM]

@@sreekumarg I followed the dimensions as indicated in the Cobweb Revealed booklet. However it took time to optimise SWR.

[@sreekumarg]

@@EI5EM OK dear. Best of luck for your experiments

[@CarmineCascone]

Hi, I saw the video, however I didn't quite cover the PVC rods from the aluminum cross that is 50 cm long as the pvc rod must be. Furthermore the holes for the bands 20-17-15-12-10 meters to what extent should be made (at which point) thanks.

[@EI5EM]

Carmine, the documentation referred to in the video give the dimensions. The distance between the open ends and the fold-back dimensions are arrived at through trial and error for low swr. This build used single wire unlike the original design but dimensions are the same. Download the Cobweb Revealed booklet for lots more info. www.dxzone.com/qsy17169-cobwebb-revealed

[@MauriatOttolink]

Excellent Video. Amongst the best. But I can't find the bit I really need...the element dimensions. I am restoring my original Steve Webb antenna. Are they exactly the same as the folded dipole variety? The speaker wiring has gone black inside the sleeving and I have rebuilt the box in its original very unsatisfactory form, the connector blocks having rusted solid TWICE. 3rd time I fixed 2 parallel copper strips (Try Rusting that!) and soldered the ends in the same pattern. Filled it solid with candle wax. Now I find the oxidised cables. Grrr! The single plus balun is going to be the answer but need the dimensions. Can't use the original cables as a measure. They've been trimmed too much. Tnx es 73 de G3NBY.

[@EI5EM]

Hello Mauriat. Download "The Cobwebb Revealed" PDF from the internet. All dimensions shown there.

[@EI5EM]

www.dxzone.com/dx17169/cobwebb-revealed.html

[@EI5EM]

Cut wires long and trim back. The gap between the ends also affects the SWR. Trim from outside, the longest dipole first.

[@harryei2kl797]

Great Video Tony and well done on the build. I'm hoping to build one next year. I see you used 20mm OD tubing, what was the inside diameter of the kit hub metal tubing? Also, is the tubing you used readily available from plumbing suppliers or did you use a specialist supplier?

[@EI5EM]

Harry, I'm not sure of the exact internal diameter of the tubes in the kit. I just know that the 20mm plastic pipes fitted inside with very little play. The antenna is now aloft so I am unable to measure. I bought the piping from a specialist pipe supplier in Rathcoole Co. Dublin www.pipeforce.ie/ I think I paid €15 for two 5m lengths. When I told the guy what it was for he just gave me the pipes and pocketed the cash :-) Best of luck with the build ... de Tony, EI5EM.

[@harryei2kl797]

@@EI5EM Thanks for the info Tony. No problem about the ID of the kit tubes, I can measure before I buy the poles. 73 de Harry/EI2KL

[@racoondiver]

good video, gi0ggy.

[@EI5EM]

Thanks for the nice comments. Glad you liked the video. The movie is not very professional but a lot of thought went into the photography and content ... de Tony EI5EM

[@Aleziss]

is it really a 1:4 or a 4:1 ?

[@EI5EM]

Aleziss, it depends on how you look at it. From the antenna side the impedance is 12.5 Ohms and the coax/rig is 50 Ohms so that is a 1:4 transformation ratio. On the other hand, from the rig side it is a 4:1 ratio. In my video I am looking at the transformation from the antenna side and the ratio is 12.5 : 50 or 1:4. Thanks for commenting. Best 73 de EI5EM.

[@Aleziss]

@@EI5EM so I could use a 4:1 balun the other way around... this is what I did find confusing a bit when researching how to do a balun, I usually find 4:1balun design...

[@EI5EM]

Exactly!

[@DxIxNxGxO]

Do you sell these at all ?

[@EI5EM]

No my friend. I built it for personal use only.

[@DxIxNxGxO]

@@EI5EM ok thank you for the reply. 73s!

[@davidnixon8106]

Talk!

[@EI5EM]

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