HOW-TO GUIDE
How to Solder a Coaxial Cable Connector With a Soldering Iron
By the OhmSavvy Research Team ·
Safety: the connector body stays hot long after the iron leaves
- A PL-259 body is a solid lump of metal. After the shield joint it can stay hot enough to burn for a minute or more, so hold the cable in a vise or clamp, never in your fingers, and let it cool before handling.
- The iron tip commonly runs at 350°C or more for this job. Return it to its stand between joints and keep the cord clear of the hot connector.
- Melting cable dielectric and flux both give off fumes. Work with ventilation or a fume extractor, and wash your hands after handling leaded solder.
Solder-type vs crimp and compression connectors
Not every coax connector is meant to be soldered. The classic PL-259 is soldered at both the shield and the center pin. Many BNC, N and SMA connectors come in several versions, and the same connector name can be a crimp, clamp or solder design depending on the part number. F connectors for TV and satellite cable are normally compression or crimp only. The table is a general guide; the instruction sheet for your exact part number is the authority.
| Connector | Common attachment methods | Where solder is used |
|---|---|---|
| PL-259 / UHF | Solder (crimp versions also exist) | Shield through the body holes, plus the center pin |
| BNC | Crimp, clamp or solder versions | Often the center pin only; depends on the version |
| N type | Clamp or crimp, varies by version | Center pin on some clamp versions |
| SMA | Crimp or solder versions | Center pin, and the shield on some solder types |
| F type | Compression or crimp | Usually none |
Crimp and compression connectors need the matching crimp or compression tool, and when they are made correctly they are reliable. Solder-type connectors suit people who already own a capable iron and only make the odd cable.
The process at a glance
01
Ring on
Coupling ring and reducer onto the cable
02
Strip
Jacket, braid, dielectric to the sheet's sizes
03
Fit body
Screw on until the pin pokes through
04
Shield
Solder braid through the body holes
05
Center pin
Solder, trim, file flush
06
Test
Continuity both ways, no short
1Gather your tools and set up enough heat
The shield joint is the hard part. You are heating a brass body that is far heavier than any circuit board joint, and it pulls heat away from the tip as fast as the iron can supply it. It sounds backwards, but a bigger, hotter tip is kinder to the cable: it brings the body up to temperature in a few seconds, while a small iron sits there for a long time and slowly bakes the dielectric.
A capable iron
A temperature-controlled iron with power in reserve. Large chisel tip for the shield holes.
Vise or clamp
Holds the cable so both hands are free and nothing touches the hot body.
Sharp stripping tools
A coax stripper or sharp knife, plus flush cutters. Nicked conductors break later.
Flux and solder
Rosin-core solder, plus extra flux for the braid and plated body.
Small file
Takes excess solder off the outside of the center pin.
Multimeter
For the continuity and short checks at the end.
Setpoints vary with the iron, tip and solder, but the shield joint typically needs a higher setting than board work; check your solder's recommendations and our soldering iron temperature guide. Plating also matters: silver-plated connector bodies generally take solder much more readily than nickel-plated ones. If solder balls up on a plated body instead of flowing, see why solder beads up instead of flowing.
2Fit the coupling ring and any reducer first
Slide the threaded coupling ring onto the cable, threads facing the end you are working on, before you strip anything. Forgetting it is the most common PL-259 mistake, and the only fix is to cut the finished connector off and start again.
A standard PL-259 is sized for thick cable such as RG-8 and RG-213. Thinner cable needs a reducing adapter that screws into the back of the body; UG-175 (commonly for RG-58) and UG-176 (commonly for RG-59 and RG-8X) are the usual part numbers, but confirm the match for your cable. The reducer goes on the cable straight after the coupling ring.
3Strip the cable to the connector's dimensions
Every connector has its own strip lengths, printed on its instruction sheet or the manufacturer's website, and they differ between connector makers and between cable types. Use those figures, not a number from memory or another brand's diagram. Each cut has its own job and its own way to go wrong:
| Cut | What it does | What to avoid |
|---|---|---|
| Outer jacket | Exposes the braid that will be soldered to the body | Scoring the braid; cut strands weaken the shield joint |
| Braid (if trimmed) | Sets how much shield sits under the solder holes | Loose strands that later touch the center pin |
| Dielectric | Exposes the center conductor for the pin | Nicking the center conductor; it can snap when flexed |
| Center conductor | Trimmed flush with the pin tip after soldering | Leaving it proud, which stops the connector mating |
If the center conductor is stranded, twist the strands tight in their original lay direction so they slide into the pin without splaying. Cut the dielectric square: an angled face leaves a gap or a bulge inside the connector.
4Protect the dielectric from heat
The dielectric is the insulating core between the center conductor and the braid, and its spacing sets the cable's impedance. Many common cables use solid or foamed polyethylene, which softens at temperatures far below a soldering tip, and foam types tend to deform more easily than solid ones. PTFE dielectric tolerates much more heat. Check your cable's datasheet if you are unsure what it uses.
- Keep dwell time short. Several quick joints beat one long one. If a joint will not flow within a few seconds, stop, let it cool and fix the heat supply rather than holding the iron on longer.
- Tin the braid lightly and fast if your connector's instructions call for it, using flux so the solder flows at once.
- Let the body cool between shield holes if the jacket or dielectric starts to soften.
- Clip a heat sink on where the layout allows; the same technique is covered in soldering wires without overheating insulation.
A melted dielectric can test fine and still be faulty
5Solder the shield through the body holes
Screw the connector body onto the prepared cable until the jacket bottoms out inside it and the center conductor comes through the pin. Look through the solder holes (a PL-259 usually has four): you should see braid, not jacket. If you see jacket, the strip length is wrong; take the body off and correct it now.
Put a little flux into each hole. Press a large tip firmly against the body right next to one hole, wait for the body to heat, then feed solder into the hole until it flows onto the braid and fills the hole flush. Move to the next hole. A good shield joint looks smooth and shiny; a dull, lumpy blob sitting on top of the plating means the body was not hot enough for the solder to wet.
6Solder the center pin, trim and file
Hold the iron against the side of the pin tip and feed solder into the end of the pin, where the center conductor emerges. A small amount is enough to fill the gap and bond the conductor. Too much runs down the outside of the pin, and a bead there can stop the connector mating or spread the socket in whatever it plugs into.
Once it cools, cut the conductor flush with the pin tip and file off any solder on the outside of the pin. Screw the coupling ring forward over the body. The cable is now finished mechanically, but not proven.
7Test the cable with a multimeter
With nothing connected to either end, run three checks with the meter on resistance or continuity. Touch the probe tips together first and note the lead resistance; on a short cable the conductor itself adds very little, so the reading should be close to that figure. If you need a refresher on the ranges, see how to use a multimeter.
| Test | Probe between | Good result | Bad result means |
|---|---|---|---|
| Center continuity | Center pin at each end | Low ohms, near the lead resistance | OL: open pin joint or broken conductor |
| Shield continuity | Connector body at each end | Low ohms, near the lead resistance | OL or high: shield joint not wetted |
| Short check | Center pin to body, same end | OL (open) | Low ohms: braid strand or solder touching the pin |
Test with the cable disconnected. Some antennas, matching networks and dummy loads show a DC path between center and shield by design, which would make a good cable look shorted. A meter that beeps unreliably on the continuity checks may be the meter or the probes rather than your joints; see why a continuity beep is intermittent.
Common coax connector mistakes
- Coupling ring left off. Always the first thing on the cable; check before every joint.
- Underpowered iron on the shield. Long dwell, a cold joint on the body and a softened dielectric all come from the same cause.
- Stray braid strands. One strand bent toward the center pin is enough to short the cable. Trim and inspect before screwing the body on.
- Solder on the outside of the pin. File it off; it can stop the plug seating or damage the socket.
- Skipping the test. A shorted cable fed with transmit power can damage a radio's output stage. Test every cable you make.
The same heat-and-wetting skills apply to any cable joint; our guide to soldering stranded wire without solder wicking too far covers the stiff spot solder leaves behind a joint, and a clean, tinned tip transfers heat far better than an oxidized one, as explained in soldering iron tip care.
Which iron suits coax connector work?
The center pin is easy for any iron. The shield joint is what separates them: you want enough power to recover quickly when a large tip meets a cold brass body, and adjustable temperature so you can turn it down again for board work. Bench stations with digital control are the natural fit. Compare the full field in our best soldering irons roundup, or read the soldering iron buying guide first.
Bench stations in our reviews
100W station with ±1°C idle stability and five presets; ESD safe, and it also drives Hakko's larger irons for big connector bodies.
85W digital, ESD-safe station (70W iron) with a heat-up time of about 28 seconds, built for dedicated workbenches and professional use.
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Frequently asked questions
What wattage soldering iron do I need for a PL-259 connector?
More than a small pencil iron. The shield joint heats the whole brass connector body, which draws heat away fast. A temperature-controlled iron of around 60 to 70W or more with a large chisel tip usually manages it, and many people use a 100W iron or larger. A weak iron forces long dwell times, which is what melts the dielectric.
Can you solder a BNC or F connector instead of crimping it?
Only if the connector is designed for it. Many BNC connectors come in crimp, clamp and solder versions, and some solder only the center pin. F connectors for TV and satellite cable are usually compression or crimp types with no solder joint at all. Use the method the connector was made for and follow its instruction sheet.
Why does my SWR reading look wrong after fitting a new connector?
Check the cable with a multimeter first. A short between the center pin and the shield, an open center conductor or a stray braid strand touching the pin all upset the reading. If the cable tests clean, look for a deformed dielectric, a center pin that is not seated, or a coupling ring that is not tightened onto the radio or meter.
Should coax connectors be weatherproofed after soldering?
Outdoors, yes. Water that gets into the braid travels along the cable and degrades it over time. Once the cable tests good, a common approach is self-amalgamating tape over the joint, often with a layer of electrical tape on top for UV protection. Keep the tape off the mating face so the connector can still be undone.
Can I use lead-free solder on a coax connector?
Yes, but it makes the job harder. Lead-free alloys melt at a higher temperature than 63/37 or 60/40 leaded solder and wet more slowly, so the connector body needs more heat and longer contact, which is exactly what softens the dielectric. Use a powerful iron with a large tip, good flux and a clean connector, and keep the heat on only as long as the joint needs it.
