When it comes to lightweight, portable antennas for VHF and UHF operations, few designs are as clever or practical as the FBK Sleeve Antenna. Originally popularized by Eric J. Methven (G1SLP), this antenna makes ingenious use of a single length of coaxial cable to form a dual-band radiator, providing excellent performance on both 2 meters and 70 centimeters.
The FBK Sleeve Antenna is a coaxial-based antenna that requires minimal materials and can be quickly assembled for field use, emergency communication, or portable operations. Unlike a traditional whip or dipole, the FBK design hides much of its structure inside the coax itself, using precise sections of the braid and dielectric to act as radiating and matching elements.
This simple yet efficient design delivers good gain, low SWR, and a clean omnidirectional pattern, all while maintaining a slim profile ideal for backpacking, field day, or portable repeater setups.
The Basic Structure
The FBK Sleeve Antenna consists of six main sections — labeled A through F in the diagram — built from a continuous piece of RG213 coaxial cable.
Each section plays a specific role:
- Sections A and C: The coaxial braid and cover are removed, leaving only the insulated center conductor. These act as the radiating elements for 2m and 70cm.
- Section B: A sleeve of braid connects the two radiators, acting as a coupling element and providing proper impedance transition between the bands.
- Section D: Forms part of the grounded shield section of the coax.
- Section E: Contains the stub, an important part for matching and fine-tuning resonance.
- Section F: Represents the total length from the connector to the top end of the antenna.
The BNC connector (female or male, depending on the feed line) attaches directly to the lower braid and center conductor, forming the feed point.
FBK Sleeve Antenna – Construction Details
According to G1SLP’s variation, the typical measurements are:
| Section | Length (cm) | Function |
|---|---|---|
| A | 36 cm | Radiator (2m band) |
| B | 23 cm | Sleeve coupling |
| C | 36 cm | Radiator continuation |
| D | 28 cm | Grounded braid |
| E | 3.5 cm | Matching stub |
| F | 128 cm | Overall antenna length |
The construction is surprisingly simple:
- Remove the outer braid and sheath on sections A and C, leaving only the insulated center conductor exposed.
- Keep the braid intact on sections B and D, soldering the appropriate joints as indicated.
- Join the inner conductor and braid properly at the feed point near the BNC connector.
- Seal exposed areas with heat-shrink tubing or self-amalgamating tape to ensure waterproofing.
The matching stub (E) helps in fine-tuning the SWR across both bands. During setup, trimming section A slightly can help achieve better resonance if required.
Performance and Applications
Once assembled, the FBK Sleeve Antenna performs remarkably well for its simplicity. It provides solid omnidirectional coverage and can handle reasonable power levels (up to 50W safely when properly constructed).
Operators have successfully used it for:
- Portable VHF/UHF field operations
- Emergency go-kit antennas
- Backpack or SOTA activations
- Temporary repeater setups
Even with a small handheld transceiver, the antenna can outperform most stock rubber duck antennas by several S-units.
FBK Sleeve Antenna – Practical Tips
- Test SWR on both 144 MHz and 430–440 MHz before sealing.
- For quick field construction, a butane soldering iron helps with braid joints.
- Always keep solder joints short and solid to prevent flexing failures.
- Use heat-shrink tubing or self-fusing tape for weather protection.
Even though the antenna looks like an ordinary coax cable from the outside, its internal geometry allows it to resonate cleanly on both amateur bands.
The FBK Sleeve Antenna demonstrates how elegant antenna engineering can emerge from simplicity. With just a piece of coaxial cable, a BNC connector, and some patience, you can create a high-performance dual-band antenna that rivals commercial options in efficiency and portability.
It’s a perfect project for experimenters, field operators, or anyone who enjoys building practical, low-cost antennas with proven on-air results.
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