3
$\begingroup$

I came across this article about torch soldering PL-259 coax connectors. It seemed like a good idea since the body needs a lot of heat to get solder to flow into the holes.

It's a little vague when describing the soldering technique for soldering the braid. It says to heat the area between two holes and after about 10 seconds the solder will flow. The problem is I can't get the solder near the holes before the flame of my little butane torch melts it away. So then I tried pulling the torch away just before bringing the solder in. But the solder won't melt unless the barrel is super hot. And then it only flows for a second. Afterwords I'm left with an overheated barrel.

It seems like a catch 22. In order for the barrel to be hot enough to flow solder it also has to be hot enough to melt coax.

A large iron directly on the hole seems a little more focused. But then the solder won't flow very far past the immediate opening of the hole.

Maybe I'm missing something about the technique.

$\endgroup$
8
$\begingroup$

Our friends in the UK and other parts of the world are now wondering how you could even begin to solder a PL259 connector with a torch (aka flashlight)! But in their vernacular, you of course are referring to a burning torch.

In general, when you heat a metallic object with the hopes of applying solder, the heat will cause oxidation to form on the metallic surfaces. This will frustrate the application of solder. A better technique is to prepare the mating surfaces with a paste type electronics flux prior to heating the surfaces. Make certain to use a flux rated for electronic components to avoid conductivity, contamination or future corrosion.

The general issue of how to heat a PL259 connector body has been a topic for decades. There is a delicate balance between applying sufficient heat so as to allow the solder to flow into the holes and the braid without using so much heat so as to melt the dielectric material or the pin support insulator. It is a skill that takes practice to perfect. Be ready to sacrifice some coax and connectors to the learning process. I have had better success soldering silver plated connectors.

One technique to avoid overheating the connector is to apply heat away from a hole while touching the solder to the hole area. As soon as the solder starts to melt, remove the heat and continue to apply solder. There is generally enough residual heat in the body of the connector to allow the solder to flow.

Some people, including me, have had success with not soldering the braid at all. Instead the braid is folded back over the outer jacket of the coax and then the connector body is forcibly screwed on so as to pinch the braid between the outer jacket and the inner threaded part of the connector. This may not be a good solution if the braid is subjected to moisture or high humidity that would promote oxidation of the mating surfaces.

More recently, crimp type coaxial connectors have overtaken most coaxial cable applications. These have the same or better reliability than solder type connectors. But the key to a successful installation is to have the correct tool, including the right die set, for the job. Here is a picture of such a tool from DX Engineering for the larger size coaxial cables:

enter image description here

There are several vendors of these types of tools. The quality tools are of a ratcheting design with changeable die sets. The connectors that are used with these types of tools look like this:

enter image description here

Once you are equipped with the right tools, you will never want to go back to soldered PL259 connectors again.

$\endgroup$
  • $\begingroup$ Hi Glenn. Yes it seems crimp type connectors are a lot more user friendly. Normally I use those, but I happen to have these solder type connectors on hand and gave them a try. I suppose I should just admit defeat and stick with the crimp types. But there's a certain sense of achievement when using the solder type. Perhaps it was an issue of not enough flux. I added some drops of liquid RA flux to the holes. Maybe a slathering of paste flux is more in order. Have you made any connectors with a burning torch before? $\endgroup$ – Paul Feb 18 at 19:50
  • 1
    $\begingroup$ @Paul It is not my first choice but I have used it before when putting connectors on outdoors during winter. It works but it is quite easy to overheat things. I added a bit to my answer. $\endgroup$ – Glenn W9IQ Feb 18 at 19:57
  • 1
    $\begingroup$ Heating the opposite side with the torch as mentioned above while applying solder to the other side. Once the solder starts to flow, remove the torch. This also works with a soldering iron. $\endgroup$ – Jim Feb 18 at 21:31
  • $\begingroup$ @GlennW9IQ sounds like "don't use PL259 but N-Type" to me; there's pretty standard crimp tools for N, too, so buying / lending one of these and using N-Connectors for outside cables (BNC for inside typically suffices) + adapters to PL259 where strictly necessary sounds the easiest and potentially cheapest way. $\endgroup$ – Marcus Müller Feb 19 at 10:05
  • 3
    $\begingroup$ @MarcusMüller I too use N connectors whenever possible. I particularly like the integral weatherproofing features. $\endgroup$ – Glenn W9IQ Feb 19 at 14:45
5
$\begingroup$

I've often used a propane torch to quickly preheat PL259s, but seldom for the actual soldering.

Once the connector is preheated, it is a quick and simple matter to flow solder into the holes and the pre-tinned braid using a 50 watt soldering iron.

(These days I use a Steinl heat gun instead of the torch flame for preheating, as it gives much better control over the temperature.)

This method minimizes the damage to the plastic dielectric and outer jacket.

$\endgroup$
  • $\begingroup$ I've heard mention of pre-heating to make soldering with an iron faster. I wonder, however, what the advantage of pre-heating is over just holding the iron to the first hole a little longer. Won't that pre-heat the body in the same fashion? Or is there a concern about overheating a focused section of the body- or perhaps sucking to much heat out of an iron with limited thermal mass? $\endgroup$ – Paul Feb 19 at 20:49
  • $\begingroup$ @Paul It will not preheat the body in the same fashion. It is my long-time (over 40 years) experience that doing it that way has a much greater potential to overheat the dielectric. $\endgroup$ – Mike Waters Feb 19 at 23:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.