RFD-CLD40, Capacitance Hats Loaded 40m Rotary Dipole.

RFD-CLD40: Capacitance Hat Loaded Rotatable Dipole (40m)

The RFD-CLD40 is a rotatable dipole antenna for the 40-meter band, uniquely designed with 32 capacitance hats constructed from short lengths of aluminum spokes. Unlike many commercially available 40m dipoles that rely on loading coils or a combination of loading coils and capacitance hats for size reduction, the RFD-CLD40 exclusively uses capacitance hats.

Why Capacitance Hats Instead of Loading Coils?

Loading coils are often used to shorten the physical length of dipole antennas. While effective for compactness, loading coils introduce resistive losses, which can significantly reduce antenna gain and efficiency. In contrast, capacitance hats allow for physical shortening without the same level of compromise in performance.

Although capacitance hats can't make the antenna as short as loading coils can, they provide a better trade-off: slightly more length, but superior performance in terms of gain and SWR bandwidth.

Performance Comparison

For example, with loading coils, a 40m dipole might be reduced to about 42 feet, but at the cost of substantial performance loss. In comparison, the RFD-CLD40 may be around 52 feet in length, but thanks to the capacitance hat design, it maintains higher gain, better efficiency, and broader bandwidth—all critical parameters for real-world operation.

In short, while loading coils may offer a shorter antenna, the RFD-CLD40 chooses performance over extreme compactness—because in the end, performance matters.

Electrical Specifications

Mechanical Specifications