Time2–3 hours

DifficultyBeginner to Intermediate

Cost$20–35

Skills NeededPipe soldering, drilling

📋 In This Guide

Materials & tools you'll need
Step 1: Calculate your dimensions
Step 2: Cut the pipe sections
Step 3: Solder the T and elbow joints
Step 4: Cap the open ends
Step 5: Build the adjustable feedpoint
Step 6: Connect the coax & add a choke
Step 7: Mount on a non-conductive mast
Step 8: Tune by sliding the feedpoint
Common mistakes
Frequently asked questions

🧰 Materials & Tools You'll Need

Copper plumbing pipe is the classic J-pole material — durable, self-supporting, easy to solder, and entirely sourced from the plumbing aisle of any hardware store. A single 10-foot length of 1/2" pipe covers an entire 2m build with material left over.

Pipe & Fittings

1/2" copper pipe — a 10 ft length is enough for a 2m J-pole
1/2" copper T-fitting — joins the radiator, stub, and mount section
1/2" copper elbow fitting — connects the stub to the T
1–2 copper end caps — weatherproofs the open top ends

Feed & Connectors

SO-239 panel mount connector
2 stainless hose clamps with machine screws — your adjustable feedpoint
Coax with a PL-259 connector
Ferrite toroid or clip-on beads for a feedline choke

Solder Supplies

Propane torch
Plumber's solder and flux
Heavy grit sandpaper or steel wool — for cleaning joints before soldering

Mounting & Tuning

Non-conductive mast — PVC or fiberglass, not metal
Power drill + small bits
Tape measure
Antenna analyzer or NanoVNA — for Step 8

📐 Step 1: Calculate Your Dimensions

Use our J-pole calculator to get the radiator length (468 ÷ f × velocity factor) and stub length (234 ÷ f × velocity factor) for your target frequency. For copper pipe specifically, a velocity factor around 0.95–0.97 is typical.

Example — 2m J-pole at 146 MHz, copper pipe:
Radiator: ≈ 36.5 in
Stub: ≈ 18.3 in
Starting feedpoint distance from the shorted crosspiece: ≈ 3–4 in (you'll fine-tune this in Step 8)

✂️ Step 2: Cut the Pipe Sections

Cut the radiator and stub

Cut your radiator and stub pieces from Step 1, leaving a small amount of extra length — a fraction of an inch is enough margin for a VHF/UHF build, since these antennas are much shorter than HF wire antennas and don't need the large trim margin a dipole does.

Cut a short crosspiece

A short section (roughly 2 inches) connects the bottom of the stub to the bottom of the radiator through the T-fitting, forming the shorted base of the J.

Cut a mounting stub if desired

Many builders leave extra pipe below the T-fitting to serve as the mast attachment point — this can come from the same 10-foot length with material to spare.

Sand all the ends

Clean every pipe end and the inside of every fitting with sandpaper or steel wool — solder won't bond properly to oxidized or dirty copper.

🔥 Step 3: Solder the T and Elbow Joints

⚠️

Use a Torch Safely, Away From Anything Flammable

Work on a non-flammable surface, keep the flame away from any plastic parts you've already test-fit, and have a way to handle hot metal — pipe stays hot longer than you'd expect after the torch is off.

Dry-fit everything first

Assemble the radiator, T-fitting, elbow, stub, and crosspiece without soldering to confirm spacing and alignment. Some builders use a scrap wood spacer between the radiator and stub to hold them parallel while soldering.

Apply flux to every joint

Brush plumber's flux onto each cleaned pipe end and the inside of each fitting before assembly — this is what lets the solder flow into the joint properly.

Heat and solder each joint

Heat the fitting (not directly the solder) until it's hot enough to melt solder on contact, then touch solder to the joint and let capillary action pull it in around the full joint.

Let everything cool, then clean off flux residue

Leftover flux can corrode copper over time and turn it green — wipe every joint down with a solvent once it's cooled.

🧢 Step 4: Cap the Open Ends

Solder a copper end cap onto the open top of the radiator (and the stub, if its top end is also open) to keep moisture out. This is a small step that meaningfully extends how long the antenna lasts outdoors.

🔧 Step 5: Build the Adjustable Feedpoint

This is the detail that makes tuning a J-pole far easier than soldering the coax directly to the pipe. Use hose clamps with machine screws instead of permanent solder connections — this lets you slide the feedpoint up and down the stub during tuning without re-soldering anything.

Attach a hose clamp to each stub leg

Position both clamps at roughly your calculated feedpoint distance from the shorted crosspiece — close enough to start, since you'll slide them during tuning.

Add a machine screw to each clamp

A small machine screw and nut through each clamp gives you a solid terminal to attach the coax leads to, without needing heat anywhere near the final tuning area.

🔌 Step 6: Connect the Coax & Add a Choke

Connect center conductor and shield

Connect the coax center conductor to one clamp's screw terminal (typically the longer radiator side) and the shield to the other (the shorter stub side).

Add a choke near the feedpoint

Wind several turns of the coax through a ferrite toroid, or slide on a string of clip-on ferrite beads, as close to the feedpoint as practical. This addresses common-mode current — a separate problem from the impedance matching the stub itself handles.

📡 Step 7: Mount on a Non-Conductive Mast

Mount the finished antenna on PVC or fiberglass, not a metal mast. This single choice prevents most of the inconsistent-SWR and pattern problems J-poles are known for — a J-pole bonded to a grounded metal mast is a well-documented source of exactly those issues.

📏 Step 8: Tune by Sliding the Feedpoint

This is the part that's genuinely different from tuning a dipole. On a dipole, you trim wire length. On a J-pole, the primary tuning control is the feedpoint position along the stub — sliding the clamps up or down changes the impedance the antenna presents to the coax.

Sweep with your NanoVNA

Calibrate for your band, connect at the feedpoint, and sweep to see your current SWR curve.

Loosen and slide the clamps

Move both feedpoint clamps a small amount up or down the stub together, keeping them at the same height as each other, then re-tighten and re-sweep.

Repeat in small increments

Small movements make a real difference at VHF/UHF — go slower than you would with an HF antenna. Most builds converge on a good match within several small adjustments.

If sliding alone isn't enough, trim the stub slightly

Stub length is a secondary adjustment — only reach for it if feedpoint sliding alone won't get you to a good match.

Lock it down once you're satisfied

Once SWR is acceptable, tighten the clamp screws firmly and consider a small dab of weatherproofing sealant on the screw heads.

❌ Common Mistakes

Soldering the feedpoint connection permanently before tuning: You'll lose the ability to slide the feedpoint, which is your main tuning control — use hose clamps until you're done tuning.

Mounting directly on a metal mast: The single most common cause of "my J-pole's SWR keeps changing" — use PVC or fiberglass instead.

Trying to tune by trimming the radiator: The radiator length sets your general frequency range; the feedpoint position is what actually dials in the match.

Skipping the flux: Solder won't flow properly into a joint without it, leading to weak, leaky connections.

Expecting one antenna to cover 2m and 70cm: See our J-pole calculator's harmonic section for why this doesn't work without a dedicated dual-band design.

← Browse all antenna calculators & build guides

❓ Frequently Asked Questions

Do I need to solder the feedpoint, or can hose clamps be permanent?

Hose clamps with machine screws can absolutely be the permanent connection — many published builds use exactly this method rather than soldering the feedpoint at all. The advantage is being able to retune later if needed, without any heat near the finished antenna.

What size copper pipe should I use?

1/2 inch is the standard, most commonly published size for 2m builds, and it's widely available at any hardware store. Larger diameter pipe is more rigid and self-supporting but changes the velocity factor slightly — if you size up, re-check your calculator's velocity factor setting.

Can I build this without soldering, using all hose clamps and fittings?

The T and elbow joints are typically soldered for a permanent, rigid structure, but the feedpoint connection itself doesn't need solder. If you'd rather avoid soldering entirely, threaded copper fittings exist, though they add cost and bulk compared to a soldered joint.

How do I know when my J-pole is properly tuned?

Sweep with a NanoVNA or antenna analyzer and look for the SWR dip to land on your target frequency, ideally under 1.5:1 at the center of your intended use. If SWR changes noticeably when you touch the coax, that points to a common-mode current issue rather than a tuning problem — check your mast material and choke placement.

Is this a good first antenna-building project?

It's a reasonable second project. The pipe-soldering and feedpoint-sliding tuning process is a different skill set than a dipole's screw-and-trim approach, and J-poles have more documented quirks (common-mode current, harmonic mismatches) than a basic dipole. If this is your very first build, our dipole build guide is the gentler starting point.

How to Build a J-Pole Antenna