Loop Construction

[gazza]

Hi
Does anyone have a method for bending 15mm copper tubing to make a 1m diam loop?
I can make this in two pieces but have still not found a satisfactory method of achieving a perfect radius.

Gazza

[steve314]

You want a 'ring roller'. It is possible to make one if you have some engineering skills/equipment. But it would probably be easier/quicker/cheaper to find a local engineering company that has one and get them to bend your tube.

There are videos about ring rollers on YouTube if you want to see how they work.

[g1hbe]

Gazza, is this for a tuned loop with a capacitor at the top or a wideband untuned (active) loop? If it's for an untuned loop, I use a plastic hula-hoop with a turn of thick wire inside.

[gazza]

Thanks for the replies.

I have now come to the conclusion that I need to find a local engineering company who can roll tubing.

It is actually for an untuned loop but of the shielded variety described by Daveb on this forum, and credited to PA0FRI, so a non metal loop will not do.

I have built a small prototype and the results without a pre-amp are very impressive, especially the low noise performance. When I have built a larger version, I will be using a well known LNA from ebay.

If anyone reading this posting, would like to try this design, I would refer you to Daveb's posting earlier on this forum.

Cheers,

Gazza

[Mike2459]

The article at PA0FRI's website has some photos of the loop being laid out along a chalked line on a piece of plywood. The results appear pretty good.

loop.JPG (51.33 KiB) Viewed 47028 times

http://www.pa0fri.com/

[gazza]

Hi,
That looks like its 10mm and easily bent. For outside use, I think you would need minimum of 15mm tubing.
I have been able to locate a local engineering company who roll in aluminium not copper and they can do it but their smallest tooling diameter is 25mm, which looks to be about the same size as some of the proprietary loops on sale. Downside is they quoting around £65 for a one off.

Cheers,


Gazza

[John6kjk]

Hi Gazza,

I have recently designed & made a Loop Antenna for TxRx on the Amateur Bands 40m to 12m. It is made from 15mm copper pipe and I rolled it myself using a home made Rolling Jig. It is very simple and uses a B&D Workmate type of Workshop Woodwork Jaws and some rollers. Let me know via the Forum if you are interested in making one and I'll post my email address. Hope this is some help.

John6kjk

[someYguy]

Another method which works well is to bend said tubing around a 55 gallon barrel, preferably an old one so that you don't mind putting a small hole in it.

Attach one end of the tubing to the barrel with a small screw or ?, and then gently walk around the barrel, bending the tubing around the circumference of the barrel. If you can't put a hole in the barrel to attach the beginning end of the tubing, then you could get a helper to hold it in place.

Works well and makes diameter about right

[gazza]

Many thanks for the ideas guys, just demonstrates the ingenuity shown by members of this forum and or my own lack of imagination.
Unfortunately I dont have access to a large barrel to use as a template or anything similar, and dont possess a workmate, however since approaching my local engineering company, they have referred me to a competitor who has agreed to roll me a loop for the price of the tube so I have accepted that offer.
I am sure that your inputs may have given other readers of this forum, food for thought in tackling construction of their own loops.

So grateful to all members who have contributed to this post.

Gazza

[Fractal1]

I used the spare wheel from my 4wd to shape my copper loop as i had no other form..lol