15m Magloop repair.

Some spare time to attend to a repair of a parallel 4-loop array for the upper HF bands today, prompted by some screen-burningly strong WSPR signals on 12 and 10m.

The loops had been soldered together onto lengths of round copper tube.  I had rushed the build and not made a very good job of it.  My failures were:

(1) Round copper tube doesn't offer much surface area to solder onto another round tube.  It's better to flatten everything and make a better joint.

(2) I hadn't paid enough attention to putting it all together in one go, with all the copper cleaned and soldered at the same time.  The soldering was, predictably, not very good.

(3) I didn't use any additional mechanical securing system.  Bolts help to keep everything stable whilst soldering, and help strength when complete.

Rushed into operation, but not very well made.

 

So, I flattened the end of the tubes, all cleaned to perfection with a rotary tool with abrasive wheel attached, and fixed these to a flattened, cleaned 15mm copper strip on either side, initially using 4mm stainless bolts.  Make sure you don't use 'Nyloc' locking nuts at this stage, because the plastic will melt and contaminate your soldering later on!

All I had to do now was solder it all up.  The key to this kind of job is to use soldering flux and keep the flame on the joint being soldered.  You can do it without flux, but if you remove the flame even momentarily, oxides will form immediately on the surface of the metal, and you won't get a good - or any - joint.  

Soldered and bolted.  Back in operation, soon!

After the whole thing had cooled down, I removed the nuts and replaced them with self-locking 'Nyloc' nuts.  Whole thing now nice and secure, with good electrical joints as well!