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A question for those of you experienced in Cobwebs.

I recovered the remnants of a Cobweb from a friends bin. It is made of white coloured GRP poles, slotted together and held with self tapping screws. Some of these joints are strengthened by alloy ferrules. The elements are typical of the G3TPW design using twinlead / speaker wire.

I intend to rebuild it, either using the original twinlead style or the G3TXQ single cable with 1:4 Guanella current balun. Whilst I decide on which design does anyone recognise the build type? Is it an original G3TPW, a copy or a home brew job?

My friend got it secondhand so I have no idea where it came from.


Thanks

My money's on That's an original

I have an original Cobweb, and I had to reinforce the joints, but used plastic sleeving. Those aluminium sleeves have most likely been a repair by one of the owners.

Thats an original. I coated mine with a thick coat of clear lacquer before it was put up, I had a couple of ltrs in the garage.

There's nothing worse than fibreglass splinters.

Gordon Bennett..... mine gave one or two then I put some rubber gloves on

Thanks all it seems a G3TPW one with twin lead wire then.
I've stripped the remains of the cobwebb. It's missing the centre alloy plate, the bit that holds it all together. I have some U bolts so I'll just have to cut and drill an alloy plate to make one. I removed or drilled out all the self tapping screws that hold the spreaders together once, disassembled I cleaned the algae off the GRP rods and inspected it. I discovered the hollow poles are split longitudinally in two places and snapped in one place. It's pultruded GRP, which explains the longitudinal cracks and the splinters in my fingers.
I fixed the spreaders by running resin into the cracks and wrapped a single sheet of glass mat around the worst damage. I've stuck it all back together again with the resin holding it rather than screws. Finally I brush 'painted' the whole lot with resin to try and keep the glass splinters at bay.

Next ... I am tempted by the G3TXQ version... http://www.karinya.net/g3txq/cobweb because....
I already have the ferrites and single core 1mm and 1.5mm copper wire, which makes it a free project. I'm thinking of trying additional dipoles for 6/4m, some people on the WWW are claiming success with that. I'm not so sure they won't interact, but it's better than watching match of the day. Or I'll change my mind and go G3TPW.


PS has anyone got the original G3TPW documentation? His website is long gone.

This will help for the tpw design http://test.g0mtd.co.uk/CB1.pdf its acopy of the G3TPW info I think, at least all the details are there.
I built the TXQ version, very easy to build and tune took about 3 to 4 hours complete.

i have the same antenna g3tpw version im just about finished refurbishing it look at my post in this section under antenna and you will see more info on mine as why I had to refurbish it and some tips from other fellow hams on what balun to use as ive opted to make a 1.1 balun for inside my jusction box instead of the coaxial one that was in it
and some pics of the state mine was in
hope this helps you

Thanks Gents.

I'm going down the G3TXQ route. I've built the Guanella 1:4 balun today, so there's no turning back.

It is an original that has been modified by additional alloy sleeving.

Do build Steve's G3TXQ's alternative single wire version as tuning it is far easier than the twin wire and wasting hours shorting out the cable with pins. The schematics for building a Cobwebb that are on the internet are wrong, the tapping points on the twin cable are wrong for the original cable as are the lengths. Steve Webb G3TPW used to have a bit of a chuckle about it when you mentioned it to him.