If you are looking to get active on the “Magic Band” without spending a fortune on commercial aluminum, the 6m Delta Loop antenna is one of the most effective and forgiving antennas you can build. It offers a low noise floor and a slight gain over a standard dipole, making it perfect for catching those unpredictable sporadic-E openings.
The 6-metre band (50 MHz) is often called the “magic band” because it can behave like both HF and VHF—offering local line-of-sight communication most of the time, yet occasionally opening to long-distance propagation through sporadic-E and other atmospheric effects.
The design shown in the diagram is a classic “apex-down” configuration. This setup is particularly clever because it keeps the heavy matching section and feedline connection near the bottom, reducing strain on your support structure.
The antenna uses about 6.10 m of wire, forming a large triangular (delta loop) shape that is supported along the top by a 2 m plastic conduit crossbar. A full-wave loop like this typically has a feed impedance in the region of 100–120 Ω, which does not match directly to standard 50 Ω amateur radio equipment.
To achieve proper matching, the design incorporates a quarter-wave transformer made from 75-ohm coaxial cable (such as RG-6). The 99 cm length of this 75-ohm coax is coiled around the PVC drain pipe and connected at the loop feed point. Electrically, this section transforms the higher loop impedance down to approximately 50 Ω, allowing efficient power transfer to the transmitter without the need for an external tuner.
Construction Tips 6m Delta Loop Antenna
The Boom
Use about 2 metres of sturdy plastic conduit as the top support. To keep the loop wire from sliding inward, drill small holes near each end of the conduit and pass the wire through them before tensioning the loop.
The Matching Transformer
The design calls for 99 cm of 75-ohm coaxial cable. When this section is wound around the 40 mm PVC pipe, it not only forms the quarter-wave impedance transformer but also acts as a simple choke (often called an “ugly balun”).
Coiling the coax helps suppress RF currents on the outside of the feedline, improving feed balance and radiation efficiency.
Connections
Join the loop wire to the matching section using good-quality block connectors (choc blocks). These connections should be enclosed in a small waterproof housing or thoroughly wrapped with self-amalgamating tape to prevent moisture ingress and corrosion.
Weatherproofing the feed point is essential for long-term stability on VHF antennas.
Once assembled, the 6m Delta Loop Antenna can be attached to a mast using a standard pipe clip on the conduit boom. Because the structure is lightweight, it can be supported easily by a telescopic fibreglass pole or even a modest wooden mast.
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