For my money its a no brainer. I built and am using Steve's (G3TXQ) version.
Construction is far more straight forward than the original. mine has up-rated toroids
to take more power, I have tested it at the legal max and it works fine. Advice from Steve
during construction was worth its weight in gold. It works a treat although its not quite as
good on 10 mtrs. Another of my hobbies is fishing so I already had some of the bits from
old fiberglass pole top kits, I also had the wire and a box full of U bolts. I think the whole thing
cost me about £70. I even got planning permission for it as a neighbor didn't like it much and
wrote to the council. When the dust settles I might even have a crack at Steve's hex beam.

Currently ordering some parts and will give Steve's design a go!

A few questions...

1. I see from the terminal box that the elements are connected to the box using solder tags. Does this mean that inside the terminal box, there are only 2 plates of metal (copper) which hold the elements in place? And one end of the balun joins these two plates together? Therefore, there are no terminals as in G3TPW's design?

http://www.karinya.net/g3txq/cobweb/cob3.jpg

2. You mention the ends of the elements are connected using spacer cords. Where are these in relation to the overall construction as I can not find them in the photo and are they necessary?

http://www.karinya.net/g3txq/cobweb/cob8.jpg

3. If I use thicker gauge wire, i.e 1.5mm rather than 1mm diameter, how much will this change the lengths of the wire I have to cut?

4. Wish me luck

Adam

Correct! But you can use any method you like to connect all the wires on one side together, all the wires on the other side together, and connect the balun output between the two.



Yes they are necessary - the two ends of each dipole must be separated, preferable by 3" or more. On the photo you can see them directly opposite the feedpoint.



The thickness of the conductor has little effect; the thickness of the insulation might change things a bit. Just like you would do with any dipole, cut slightly long and then trim it to get the SWR minimum where you want it.



Good luck

Steve G3TXQ

Excellent, thanks Steve.

Made up a list of stuff that I need for the cobweb, so will get some parts ordered tonight and collect some stuff tomorrow.

Two more questions and I should be good to go...

1. What should the spacing between the wires be and how do you calculate this?

2. I was thinking of making the inner "x" of the antenna with 25mm PVC conduit pipe, then making the additional four 66" lengths from 20mm PVC conduit pipe, as I cannot find 0.75" and 0.5" diameters of fiberglass tube anywhere. There may be some play when the 20mm is inserted into the 25mm, but I could wrap some tape around the 20mm to give it a snug fit. Questions is, can I use PVC or must it be fiberglass?

Many thanks
Adam - MM6HUT

It's really just a case of laying each dipole on the frame and adjusting until it looks "square". The "Centre-to-corner length" on my web site shows you where the wires for each band "sit" on the spreaders. That's a good starting point but don't attach the wires permanently at that stage. When you start tuning you might want to adjust them a bit. Nothing is very critical here - you're trying to get each dipole to sit symmetrically on the support frame, with end spacings not less than 3".


The first one I made used PVC tubing. It's just as good as fibreglass from an electrical perspective, but it has a tendency to sag when it gets warm in the sunshine. The antenna still works, but the tuning changes a bit and it looks a mess!

73,
Steve G3TXQ

Try Sandpiper antennas, I think they cater for CobWebb homebrew.

AMTOOLS UK from Wigan do cobweb parts.
full fibreglass pole set £24.45, inc control box pole.
centre plate kit complete £18.75.
he also does the ferrite toroids, price will depend on which ones you use.
The plastic hobby box to house the balun was more of a problem to find
than I expected, Got it from e-bay in the end £1.75
Amtools can be found on e-bay or http://www.amtoolsuk.com/joomla/
or amtools@ntlworld.com Its run by Les G4HZJ.

Rob G7SVW got one of these, a bit fiddly to tune, got there in the end with the help of an analyser.
2-3 's' points up on his Hustler vertical, lower noise floor too.
not sure where the claim of 2K power handling comes from, it's got RG58 in the box for Christ's sake!

all in all, he's ahppy with it for the money.

I bought one at the buy it now price - still can't see any £100 starting bid options.

Very happy with mine - when I used it. I don't get on HF much at the moment but it is a great antenna once up in the air and tuned.

2k power handling NO.400w in set it on fire,not so happy now

after steves advice when i had mine, i replaced the coil of rg-58 from inside the box and put an external one of rg-213 and it handled the legal limit with no problem.

If you haven't already seem it you might get some tips off my build http://www.hamradiodeals.co.uk/forums/viewtopic.php?f=43&t=19002 the 20m string as gone on mine ,its been like that a couple of months now ,dam weather.

Thanks everyone, finally built my 2m yagi, 6m dipole and my 1/4 vertical. So I suppose it's time for the Cobweb.

Having a look at the table posted in the link here from amtoolsuk, I was wondering about the number of poles which come with the kit.

http://www.amtoolsuk.com/joomla/index.p ... t&Itemid=1

It says 4 x section 4 and 5x section 5. Won't this be too many poles?

Each side of the cobwebb should be around 3.53m long, so you will need a little less fiberglass pole if using aluminium tubing for the middle support.

Would I be better just buying some of these, assuming they are the same diameter as the ones from amtoolsuk?

http://www.lathams-fishing.co.uk/latham ... pid12.html


Adam

The spreaders on my cobweb measure about 3850mm across the diagonal, or 1925mm from the centre to the tip. The two section need to overlap each other a bit, and they need to be inserted into tubing used as the centre support; so 2x1110mm for each "arm" is generous, but not excessive.

So, including the pole that holds the junction box, they are talking about the right number.

73,
Steve G3TXQ

I repaired mine last weekend and when taking it down the poles got jammed up in the guttering on the walls ,basically they got some hammer ,i was expecting the poles to break but easily survived it.
I got mine from hamtools ,they might be more expensive but at least you get the right thing for the job.
I replaced all the strings with strimming line and for some reason the swr is better especially on 12m where it was way off, i even got it a little higher and its working great.