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Author Topic: HELP! PL-259/RG-58 coax jumpers keep failing!  (Read 4697 times)
AG4DG
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« on: January 09, 2008, 12:10:10 PM »

I follow the procedure described in the 2001 edition of the ARRL handbook (page 22.7, figure 22.18) for installing PL-259 connectors on RG-58 jumpers.

Unfortunately, my coax jumpers keep failing sooner or later for reasons I can't possibly fathom.  It may take a few days, a few weeks, a few months, or a few years, but my coax jumpers inevitably fail.  And it's not just because of moisture getting in, because I've had jumpers I never took outside fail on me.

Where am I going wrong?  I know to always make sure to verify the short between the inner elements, the short between the outer elements, and the open between the inner and outer elements.  But there must be some kind of flaw in the way I do things that causes something to deteriorate.

One problem is that I have no idea how to figure out what went wrong, especially when the failure is intermittent.  I have no idea how to figure out which end of the coax is the problem end.

Is anyone here a master of soldering PL-259 connectors on RG-58 coax?

PLEASE do NOT suggest I switch to a differnt kind of connector or different kind of coax.  I use RG-58 for short jumpers because it's flexible, the line loss isn't significant (due to the short length), and I can't work with any other kind of coax.  (Trust me, I tried to solder PL-259s on RG-213 once, and I couldn't do it.  Even a fellow ham who was very experienced at this found it difficult, though he was able to do it successfully.)  And don't suggest I switch to N connectors.  All my radios, antennas, and other accessories have SO-239s, and I'm not going to switch everything willy-nilly.
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WA3SKN
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« Reply #1 on: January 09, 2008, 12:20:23 PM »

Is it the center conductor or shield connection that is failing?  You can check this with a VOM (ohm meter) while you wiggle the wire (alligator clip jumpers can help here!).  One or the other is probably opening up... and probably due to a cold-soldered connection.

-Mike.
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WB6SSW
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« Reply #2 on: January 09, 2008, 12:38:50 PM »

Problems are usually with the coax braid solder connection.  Some suggestions:

Use a good quality coax with a real braided shield designed to be soldered to the PL-259.  Some RG-58  just won't work with soldered connectors.

Make sure you're using the right RG-58 adapter for the PL-259, the UG-175/U.  The RG-58 should fit somewhat snug into the adapter and the adapter should screw easily into the PL-259 (I've run across some PL-259's with oddball threads that won't properly take a UG-175/U).

Use good quality name brand PL-259's.  Some no names won't properly take solder on the barrel and the insulation between the tip and the barrel will melt before the barrel connection is properly made.

Rough up the area around the barrel soldering holes and the UG-175/U with emery cloth, etc.  This insures a good soldering bond.

Use rosin solder flux.  Yeh, I know that you use rosin core solder, but separate rosin flux really does help.

Use a hot iron;  that's a lot of metal in that barrel that you're heating up.

Hold the connector in a vise by the tip or the coax when soldering the braid, not by the barrel.

Good luck.
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W5JI
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« Reply #3 on: January 09, 2008, 12:40:05 PM »

Assuming you are using the correct adapter for the RG-58 with the PL-259 and following the handbook directions, most likely the issue is not using a soldering iron (no gun) with sufficient heat to bring the connector body and coax shield/center conductor up to proper temperature for soldering. You need a minimum of a 100 watt iron and I use a 300 watt iron myself.

The secret is to have a powerful enough iron to bring the connector/coax up to soldering temperature quickly. A small iron or gun will take so long to heat the connector/coax that you will most likely damage the coax by melting the insulation between the shield and center conductor.

Also, be sure you are using an old style 60/40 solder with tin and lead. The newer, politically correct solders will actually fail to wet the connection(s) correctly. Also, I suggest you use a good rosin flux (either a powder or liquid) on the shield before applying solder to help the solder flow.

If there is a ham club or you have access to an older Elmer, have someone construct a couple of jumpers while you watch to see if you can pick up some pointers. If it was easy, there would not be so many articles about how to do it correctly......

73.....Jim  W5JI
 
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AC5UP
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« Reply #4 on: January 09, 2008, 12:49:36 PM »

Intermittent is the word that jumped out at me and that makes me think cold solder joint or internal short. Any chance you're using a slaughtering gun (spelling intentional) or a 25-35 watt pencil iron? Might also check your solder to see if it's 60/40 and not 40/60. 60/40 solders much easier and both are common.

If so, you might want to consider soldering only the center pin. Prep the coax as normal, make sure you have enough braid folded over the reducer that it will make a reliable compression contact with the PL-259 shell, tighten securely, solder the center pin. On small coax like '58 I've been known to trim the center conductor long and fold it over so I have some extra metal inside the sleeve. Makes it more likely the solder will bond the two together.

It's very easy to get a cold joint with a soldering gun, very easy to melt the dielectric with a small iron that takes forever to bring the shell up to temperature. That will get you an internal short.

I've also come across cheap PL-259's that are solder resistant. Started buying the Amphenol nickel plated jobbies at Hamfests as they're not that expensive when you buy a dozen at a time. The QC is consistent and I've had good luck with them.
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DA2KI
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« Reply #5 on: January 09, 2008, 12:53:06 PM »

What type of RG-58 coaxial cable are you using?  The basic RG-58 cable has a solid center conductor.  RG-58A has a stranded center conductor.  I prefer a stranded center conductor because they tolerate flexing better.  RG-58 cable with a solid center conductor can suffer a break in the center wire that is not noticeable from the exterior of the cable.  The problem can be detected using a multi-meter / continuity tester connected to the center pin of both PL-259 connectors.  Flex the patch cord and see if the continuity is intermittent.  This condition will also cause flakey SWR problems (again, flex the cable while watching the SWR reading.  It should not change.)

Also use only quality connectors.  There are a lot of junk PL-259's out there.  Stop by a 2-way radio shop and see if they sell PL-259 connectors made by Amphenol.  They will cost more than the cheap Radio Shack versions, but their center insulators will not melt as you try to solder them.  Amphenol is to RF connectors as Belden is to coaxial cable (both are very well known and respected names in the business).  Various Amateur Radio dealers (AES, HRO, etc.) also carry Amphenol brand connectors.  Ask for them by name! (or end up with the cheap stuff!)
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K4JSR
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« Reply #6 on: January 09, 2008, 01:20:53 PM »

John, DA2KI, has it 100% correct! If you are using regular Rg-58 with the solid wire center conductor you are begging for failures.  The solid conductors in
RG-58 will break due to metal fatigue after a certain
amount of flexing has occurred.  Short patch cords by their nature do lots of flexing.  
There are at least two ways of approaching a remedy:
1. Make the patch cords long to allow for some stress relief at the flexing radii.
2. In addition to the above start using RG-58-AU or CU
which has a stranded center conductor that is more conducive to flexing
Of the two methods above, I heartily recommend going to RG-8X. It is cheap and much sturdier than RG-58.
Life is too short to be continually making and breaking patch cords!

73 and good luck!   Cal  K4JSR
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AG4DG
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« Reply #7 on: January 09, 2008, 01:39:34 PM »

Thanks for the suggestions, everyone.  The RG-58 coax I use has stranded wire for the inner conductor.  My soldering iron is a Weller temperature-controlled kind (around 50W, I think).  I'm going to first try the suggestions that do NOT involve buying more equipment.

Some more questions:
1.  AC5UP: You suggested soldering ONLY the center pin.  Would the coax cable last if I neglect to solder the braid to the connector through the 4 holes on the side?  I thought you're SUPPOSED to fill those 4 holes with solder so that the braid bonds with the connector.  Why would these holes be provided if they're so inferior?
2.  K4JSR: How long should my cables be to avoid flexing?  What should the minimum length of my jumper cables be?  3 feet?  5 feet?  10 feet?
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AC5E
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« Reply #8 on: January 09, 2008, 02:34:36 PM »

If you do not find a way to get enough heat to your PL-259's it would be a really good idea to budget for premade jumpers.

It takes far more heat than a 50 Watt iron of any sort can supply to heat both the shell and the shield enough so the melted solder can wet the surface of both. If the solder does not wet both the shell and the shield you get a surface contact situation, where you have a mechanical solder bridge between the two that is not a solid electrical contact.

Much like sticking a screwdriver in there. Sooner or later a bit of corrosion will lift the solder off the shield or the shell - and you have an open connection.

The soldering iron I use here is a 150 Watt American Beauty I picked up at a yard sale for five bucks. It normally takes six to ten seconds to achieve wetting.

The "Iron" I use for production work is a 1 KW Hexacon resistance soldering rig that does the job in less than two seconds.

I also have a 500 watt resistance rig I bought off the big internet auction for thirty bucks that does the job in about five seconds. As well as several other "big irons" ranging from a 250 watt "hatchet" style Hexacon to a 3 pound "soldering copper" that I heat with a blowtorch. Any of these will get the job done properly and more or less rapidly.

But what will NOT get the job done is any of the assortment of Weller and Wen soldering guns and any of the 15 to 75 watt temperature controlled rigs I have in the shop. With enough time and patience you can get an acceptable appearance - but that is all.

For more information on soldering in general, let me suggest you borrow a copy of "Solder and Soldering" by Howard Manko from your library. Manko is the recognized expert on the subject.

73  Pete Allen  AC5E

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KZ1X
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« Reply #9 on: January 09, 2008, 02:38:44 PM »

W5Ji must be able to read my mind.  His response was truly great and comprehensive.
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AG4DG
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« Reply #10 on: January 09, 2008, 02:51:45 PM »

How do you tell if your coax jumper is PROPERLY soldered together?  How am I supposed to do a good job when I can't tell if I did a good job or a lousy job?

I don't think buying premade jumpers is such a great value.  There are SO MANY accessories you can have in a shack (switches, tuners, noise cancellers, relays, meters, etc.).  The only premade jumpers I buy are the long low-loss lines since the RG-213 and other low loss coax is much more difficult to work with, and I only need a few of these.
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KE4DRN
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« Reply #11 on: January 09, 2008, 04:18:52 PM »

hi jason,

you test your coax connections with ohm meter,
you are doing the task properly, your solder iron
is the problem, it is wrong tool for the job.

search on ebay for  weller 100* iron
you will find many available for about $ 50 plus s/h.

Invest in this tool and your connector problems will disappear !

Weller 100W (or equal) is the difference between a
HEAT SOURCE and a HEAT SINK.

After you make your first connector with the Weller,
you will not be disappointed !

Good luck with the projects.

73 james
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AC5UP
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« Reply #12 on: January 09, 2008, 04:26:49 PM »

If you don't have a large iron capable of generating enough thermal mass to go in hot and get out quick you will melt the dielectric. Yes, you are supposed to solder through at least one or more holes in the PL-259 shell but with a lightweight coax like RG-58 the chances of damaging the coax from heat are greater than the risk from a bad compression contact with the braid.

That's why I suggested you try it. Make up a jumper with only the center pins soldered and see if it holds up. If not, you can always solder the shell later. Twist the braid around the reducer in the same direction as the shell will tighten and make sure there's enough of a 'wad' to crunch down when tight. You might also consider a light tinning of the braid to add a bit more mass inside the shell, but not so much that it can't squish down easily.

I use a Weller 85 watt iron with a chisel tip ($25 at Lowe's last time I looked) and if you have a local store catering to stained glass hobbyists they will have big irons in stock. I've had very poor luck with foam RG-8X on a PL-259 as it melts much too easily and haven't soldered the braid with 8X for a few years because of that. No problems so far.

BTW: If someone hasn't mentioned it yet, always solder the center pin first. With RG-213 in particular the connector will try to unscrew itself when heated if the pin isn't soldered first.

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AC5E
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« Reply #13 on: January 09, 2008, 04:42:25 PM »

A 100 Watt soldering iron, NOT a soldering gun, is barely adequate for the job. It will take far too long to transfer enough heat to do the job and you run the risk of melting the dielectric and possibly shorting the coax.

A 150 Watt iron is only a couple of bucks more and will get the job done much more rapidly. A 185 or 200 is even better. Locally, builders supplies, plumbing supplies, and hardware stores stock them or can get them. I seldom visit a flea market, estate sale, or a major garage sale without seeing at least one well used iron for sale. And as a last resort there is always that big internet "auction."

If you have enough heat on the "work" the solder will flow pretty much like water. If you take it easy with the solder for a half second you can see the solder flowing through the hole in the shell and wetting the braid. The  shield wires will be "tinned." At that point you can step  up the amount of solder to fill the interstice between the shell and the braid. As soon as the hole is filled to nearly flush to the top - stop. Leave everything alone for 30 seconds or so to give the solder a chance to cool without crystallizing.

It will take a little practice to get it perfect. But it's not hard if you have the right tools.

73  Pete Allen  AC5E
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WA9SVD
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« Reply #14 on: January 09, 2008, 05:01:10 PM »

Interesting perspective.  The "OF's" have a solution that has served well, and they don't have problems.  
Newbies have problems, and have other newbies giving advice about "short cuts" and easier ways around those of the OT's, and the newbies, and those giving the newbies short cut suggestions have problems with coax connectors.

    IS there a pattern here?
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