Cobwebb Mk2

Since having the stroke I have plenty of time on my hands recovering. So I'm going to make another Cobweb Antenna but cheat slightly with the frame as it will already be made up, this is because my coordination is not so good at the moment so I'm having ago at cheating! But if you want details my blog will supply plans for potential builders! The cobweb will be that of Steve Webb's design a G3TPW. Although a little heaver in the frame is design, I have used it with strength in mind, especially up here where I live at windy ville hill!

So watch closely now as I begin the build.......You'll need two terminal blocks each 12 spaces long, plus one Junction box about 150x 80x50mm. See how I start with interlinking the links of one the terminal blocks 2,4,6,8,and 10 with some bent wire. Links 3 ,5,7, and 9 are linked via a straight piece of wire. You need to do both terminal blocks so you end up with something like the below:

Terminal blocks are connected via some copper wire

Offer up the box to the terminal blocks

Terminal blocks now fixed in to the box by 4 screws.

Now you'll need some sort of pole to take junction box on the frame, I chose a fibreglass pole I picked up off Ebay a while back, see below.

Now I start on The Element wire, cutting out the tapped points,here's one I prepared earlier:

Notice how I marked up the measurement first and then cut out half an inch of the cover. Then I cross over the wire so it's touching each other and then solder. Complete all of the tapping for the elements like this.You should now have the junction box made together with the elements cut and tapped. so the whole completed box elements and bar should look like this:

Excuse the rug its old and very 1970s colour!

Once you're happy that the junction box has the correct contacts and all is tightened up you can make waterproof by adding some sort of silicone base paste or grease to the box,after adding the coax which has 6 winds around the box and acts as the reducer to 50 ohms you can then place the lid on the box, the junction box is now completed.

Now on to the frame, it is a fixed metal plate with 4 retractable legs made out of fibreglass tubes that slot in to each other.The legs are fixed on to the frame via bolts and it is fixed to the mast from the central position. 

Well I have taken a look at the frame and it will just not right, It's just too heavy and it sags in all the wrong places, the designer had the right idea but couldn't put it in to practise. 

So I have ordered some parts off ebay and am waiting for them to arrive which will be some more lighter fibreglass poles and an aluminium plate 200mm x 200mm. I will re-build the frame to my specifications. I don't think I'm being a pain, but I know what works and what doesn't and the original frame works!

So there you go it's that simple, even someone who has recently had a stroke can build a G3TPW cobweb ! And as a present to myself I've bought a new radio to go along with the antenna! A Kenwood TS 570D nothing special, but will make a good 2nd radio!

SOMETIME LATER:

Well I have checked the G4TPW SWR measurements and they seem slightly out most because I'm using a larger frame, to be honest in the present state I'm in with the stroke recovery process in full swing I' not really in the mood for fixing the problem at the moment far better to wait until I feel more like doing it. |Hey ho that's the way it goes I'll store the G3TPW for the moment and work on a G3TXQ version, a slightly easier design for me at the moment.

I'm still waiting on the balun for the G3TXQ but the frame and some of the elements are looking good.

OK the Balun arrived a day later and I've sorted it in a new junction box and I've added the 10 bolts on top of the box so the junction box is now complete. So much easier than the G3TPW junction box!

The elements have been made up and are ready to be placed on the junction box.

On to the frame now;

The plate I got from ebay and is 200mmx300mm a good size that provides plenty of room with the poles. You'll notice in the end I went with wooden poles from previous versions this was set up with the eyelets from the last project I was completing. At last its beginning to resemble a cobweb antenna 

With the frame in place I wired in the elements and then did a quick check on the MFJ Meter the readings were not bad but the wooden poles looked shabby and unprofessional so I changed them for the new fibreglass ones I had just got off ebay, the antenna looked much better.

Once the antenna was set up ready on my test pole I completed the tuning. The strange thing is that when I switch from my old Cobweb and to the new one there is little difference so I did a quick check of the old antenna with the MFJ to see it was still set up correctly, it was perfect! so it must be location of the testing pole. Still, I must admit it's not a bad project to do whist recovery from the stroke!