2.4kW High Power 4:1 Balun For Windom / OCFD Wire Antennas

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Note for Windom / OCFD Antenna Users

While a 4:1 balun is traditionally associated with Windom-style off-center-fed dipoles (OCFDs), it's important to know that this is based on old assumptions that don't hold up well in practice.

A Windom is not a balanced antenna, and a 4:1 balun — which tries to enforce current symmetry — is often inefficientin this application.

For significantly better performance and lower losses, we recommend using a:

• 4:1 UNUN (for impedance transformation)
• 1:1 line isolator (choke) placed at 0.05 λ from the UNUN (to suppress common-mode currents)

This approach splits the two functions — matching and isolation — allowing each component to do its job properly. The result is improved efficiency, reduced heating, and better pattern stability on all bands.

A 4:1 balun combines both functions on a single core and often struggles under asymmetrical, multiband conditions, especially at higher power or off-resonant frequencies.

Function

• 4/1 High Power Dual Core Current BALUN with two side installed eye bolts for strain relief of the antenna wires.
• Real Guanella type DUAL CORE current BALUN.

Mechanical Characteristics

• Optimized 61 mm diameter toroidal ferrites
• Heat resistant teflon coaxial cable with high breakdown voltage.
• Professional 50 Ohms N-connector or SO239 connector. (IP64 after sealing with self- vulcanizing tape or equivalent).
• Stainless steel M6 antenna connections and Stainless steel eye bolts. Stainless steel type 316 More info.
• Waterproof (IP64) and shock proof polycarbonate UV resistant enclosure. More info.
• Weight: +/- 500 g.

Electrical properties

• Conservatively rated 4/1 transmission line transformer.
• Operation principle: Coaxial Common-Mode Choke.
• Very high common-mode impedance. (Substantially higher than what’s obtainable with the “beads over coax” approach).
• Max. power:
• 2400 W PeP @ VSWR < 2.0/1 (ICAS)
• 1200 W PeP @ VSWR < 2.0/1 (CCS)
• 850 W PeP @ VSWR < 2.0/1 (DIGITAL FT8/FT4)
• For ICAS and CCS power definitions, More info
• Deployable frequency range: 1.5 to 30 MHz.
• Intrinsic VSWR : < 1.15 / 1 at the frequency range edges.

General BALUN user installation guide & safety instructions