Loop Construction

Useful information regarding antennas for SDR products.
gazza
Posts: 4
Joined: Mon Oct 01, 2018 12:16 pm

Loop Construction

Postby gazza » Mon Oct 01, 2018 12:23 pm

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
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steve314
Posts: 2
Joined: Thu Sep 21, 2017 10:14 pm

Re: Loop Construction

Postby steve314 » Mon Oct 01, 2018 9:16 pm

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.
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g1hbe
Posts: 367
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Loop Construction

Postby g1hbe » Mon Oct 01, 2018 10:21 pm

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.

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Andy

gazza
Posts: 4
Joined: Mon Oct 01, 2018 12:16 pm

Re: Loop Construction

Postby gazza » Tue Oct 02, 2018 7:48 am

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
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Mike2459
Posts: 124
Joined: Mon Jul 24, 2017 8:24 pm

Re: Loop Construction

Postby Mike2459 » Tue Oct 02, 2018 7:56 pm

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
loop.JPG (51.33 KiB) Viewed 2956 times


http://www.pa0fri.com/

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gazza
Posts: 4
Joined: Mon Oct 01, 2018 12:16 pm

Re: Loop Construction

Postby gazza » Thu Oct 04, 2018 8:36 am

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
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John6kjk
Posts: 1
Joined: Fri Oct 05, 2018 8:45 pm

Re: Loop Construction

Postby John6kjk » Fri Oct 05, 2018 8:59 pm

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
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someYguy
Posts: 93
Joined: Sun Apr 10, 2016 7:12 pm

Re: Loop Construction

Postby someYguy » Fri Oct 05, 2018 10:36 pm

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 :)

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gazza
Posts: 4
Joined: Mon Oct 01, 2018 12:16 pm

Re: Loop Construction

Postby gazza » Sat Oct 06, 2018 8:39 am

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
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Fractal1
Posts: 58
Joined: Sun Feb 21, 2016 6:06 am

Re: Loop Construction

Postby Fractal1 » Sun Oct 14, 2018 3:25 am

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

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