The J-Pole antenna using 300 Ω TV Ribbon line is a simple, lightweight, and very effective antenna for VHF operation, especially for the 2-meter amateur band. With no ground radials required and an easy feed arrangement, this antenna has become popular for portable use, emergency setups, apartments, and antenna-building events. The attached diagram illustrates a proven design that has been successfully built and tested by many amateurs.
J-Pole Antenna Concept
A J-Pole antenna is essentially a half-wave radiator fed by a quarter-wave matching stub. In this design, both the radiator and the matching section are formed from a single length of 300 Ω twin-lead. The balanced nature of the ribbon line helps keep construction simple while providing a convenient way to tap the feed point for a 50 Ω coaxial cable.
Unlike a simple dipole, the J-Pole can be fed at the bottom and mounted vertically without a ground plane, making it very practical for temporary or indoor installations.
Construction Details
The antenna is made from a continuous length of 300 Ω twin-lead. The top end is sealed and may include a small hole for hanging the antenna from a string or nylon cord. Near the lower section, a short cut is made in one conductor to form the matching stub gap, as shown in the diagram.
The feed point is created by soldering the coax center conductor and shield across the twin-lead at the specified distances. These dimensions are important because they determine the impedance match. Once soldered, the twin-lead wires are folded over each other at the bottom and soldered together to complete the stub.
The antenna can be fed using RG-58 or RG-8X coax, and no external balun is required for most installations.
J-Pole Antenna Dimensions
The total length of the twin-lead radiator is approximately 1405 mm. The matching stub section measures about 420 mm. A small gap of 3 mm is left in one conductor to form the J-Pole structure. The coax feed point is tapped roughly 28 mm above the bottom, with the coax exiting at an angle for strain relief.
These dimensions are optimized for the 2-meter band and typically provide a good SWR across most of the band without adjustment.
Performance and Use
In real-world use, this twin-lead J-Pole performs very well for both FM and simplex operation. Mounted vertically, it provides a low take-off angle suitable for local and repeater contacts. Because it lacks radials and uses lightweight materials, it is ideal for:
- Emergency communication kits
- Portable and backpack operation
- Indoor or balcony installations
- Field Day and antenna-building workshops
When installed clear of metal objects, users often report performance comparable to commercial vertical antennas.
Weatherproofing Tips
For outdoor use, it is recommended to seal the top end and solder joints with heat-shrink tubing, liquid electrical tape, or silicone sealant. This prevents moisture from entering the twin-lead and affecting performance.
Credit and Original Sources
This article and the attached diagram are based on material originally published by EMRG (Edmonton Microwave Radio Group).
Original documentation and antenna party resources can be found at:
Full credit goes to the original authors for sharing this practical and well-documented antenna design with the amateur radio community.
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