Important tips for home brew stuff

Important tips for home brew stuff

Postby Notion » Wed Mar 03, 2004 4:41 pm

Having read loads of articles about making your own antennas from trying to improve transmitting and receiving better signals, I wanted to write this article as very few of all the designs out there actually emphasise the importance of good soldering and having a sound electrical connections.

Its all very well having lots of pics and details on dimensions and calculations which say solder this bit to this and that bit to that, but without a good connections it ...well really means nothing.

I have seen so many pictures from links that are supposed to the be best designs and antennas (which Im sure they are) but if you see some of the soldering that has been done on these home brew designs, its a wonder they actually work at all.

The idea when soldering two metals of the same material together is to form one continuous piece. That is when a good soldered joint is achieved, there is also a good electrical connection also.

As an example if you were to take a small piece of copper plate and solder another to it, it should take considerable effort to break the soldered joint if the original joint was soldered properly.

When using solder to join two pieces of the same material together (i.e. copper) there is no excuse for globules, lumps and bumps and dry or 'cold' joints.

<b>Dry or Cold joints</b>

A dry or sometimes called a 'cold' joint occurs when the two materials to be joined have not been sufficiently prepared before making the joint, or the two materials have not been sufficiently heated.

The solder may look as though it has 'joined' the two materials together but in fact all that has happened is the solder may have looked as though it has flowed but actually all that is holding the join together is the sticky flux, and therefore making little if not any electrical connection.

<b>The right type of heat</b>

A lot of the 'home-brew antenna' designs on the net say use soldering irons to 'solder the joins' but rarely state that soldering irons come in different wattage's. It would be fine to use a low wattage soldering iron to join a fine wire to a circuit board on a bug, but totally useless to use this for such things as making a biquad with copper pipe and plain copper or circuit boards. In order to join a copper pipe to a copper plate you basically need more heat.

<b>Using a blow torch</b>

This article is based upon the design of Trevor Marshalls biquad antenna constructed from the design found here:-

I will say at this point that I design websites and not antennas, so don't ask me how it all works...but I do understand how to solder.

Trevor Marshalls website has all the deatails for that. I am just concentrating on the actual construction techniques.
So back to the blow torch... when I made my Biquad (Based upon the link above) I found that the easiest way (for me that is) to join a copper pipe to a circuit board, was to use a blow torch.....Nothing fancy but just something that can give that extra little bit of heat.

But... there is a technique that you must employ.
Once you have your copper pipe in place ready to join to the circuit board...make sure it is very clean and totally free of grease. You can do this by spraying the join to be soldered by using a solvent or 'degreaser' this will evaporate leaving a clean and grease free area to join.
With the pipe and circuit board in place heat the pipe and NOT the circuit board.....there will be enough heat transmitted to the circuit board from the pipe to form a perfect join.

Its all a matter of experience, but you can tell when the join is ready for the solder to be applied. The copper will dull slightly and may change colour. The best thing to do is to test this by using some scrap pieces to work on first.

If you have a clean area to join...the right heat... and solder that has flux in its core, then when the solder is applied the heated joint.... it should flow like magma out of a volcano ... sticking to everything in its path and forming seamless joins.

One other tip.. if you know before hand where you are going to have to make a join, by applying solder to the area first, (this is sometimes called tinning) this will make it much easier when it actaully comes to solder two materials together.Image

Soldering is a bit like surface tension with water, you can have globule of water on a dry table that will just sit there, but if you put another drop next to it and carefully using a pencil or something slowly drag one globule to the other... they will suddenly merger together froming one big globlule.

I know this is a lot of text and not a lot of pics.... but if you want me to make a detailed page about this subject then leave a post.

The picture here is a biquad I made from the the design shown at the link in this article, (above), but I have changed it slightly from Trevors design in that I have used much thinner coax cable and so had to solder the outer coax cable directly to the main copper pipe. The basis is exactly the same, but note that the INNER cable of the coax is ONLY attatched to the bent copper wires, and NOT the copper PIPE... very important that!!

I have not tested this set up as of yet, but once I have given my laptop a go with and without the the biquad, I will post the results here.

The results will not be about db's or gain, but about distance and if I got a signal or not... as I mentioned before Im not a guru on data and antennas..... I just want results ... :)
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Postby digiital » Thu Mar 04, 2004 7:51 pm

It's really called a cold solder joint. Atleast thats what we call it at work.

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Postby lincomatic » Tue Apr 27, 2004 8:02 am

good tips but i have some comments:

1) for electrical connections, a blowtorch is really not the optimal soldering tool because it's so hard to control where the heat goes. a soldering iron allows you to more easily direct the heat away from stuff that melts, such as the wire's jacket. A 50W+ iron w/ a fat tip should work ok.

2) the outer braid connection looks cold-soldered to me.
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