Carolina Windom Antenna in Amateur Radio

The Carolina Windom is a popular, multi-band wire antenna that takes the traditional Off-Center Fed Dipole (OCFD) and gives it a specific twist: it intentionally uses a section of the coaxial feedline as a vertical radiator. This hybrid design gives you the high-angle radiation of a horizontal wire (great for local NVIS contacts) combined with the low-angle radiation of a vertical antenna (excellent for DX).

Anatomy of a Carolina Windom

Unlike a standard dipole that is fed exactly in the middle, or a standard OCFD that just tries to find a good impedance match for multiple bands, the Carolina Windom relies on four specific components to shape its radiation pattern:

1. The Asymmetrical Horizontal Wire: The main wire is fed off-center, usually at a 37.5% / 62.5% split (sometimes 33% / 67%). For an 80m version, this means one leg is roughly 45 feet and the other is about 88 feet.
2. The 4:1 Matching Transformer: An off-center feedpoint has a higher impedance than a center feedpoint (closer to 200–300 ohms). A 4:1 voltage or current balun at the feedpoint steps this down closer to 50 ohms.
3. The Vertical Radiator: This is the “secret sauce.” A specific length of 50-ohm coaxial cable (often 10 feet for a 40m version, or 22 feet for an 80m version) drops straight down from the 4:1 balun. The shield of this coax is intentionally allowed to carry common-mode current, turning it into a vertical radiating element.
4. The Line Isolator (1:1 Choke): Placed exactly at the bottom of the vertical radiator, this heavy-duty RF choke stops the common-mode current cold. It prevents the RF from traveling any further down the coax shield and entering your shack, keeping your audio clean and preventing “RF in the shack” bites.

Why the Vertical Radiator Matters

When you put up a standard horizontal wire antenna, especially on lower bands like 80m or 40m, it’s very difficult to get it high enough (at least half a wavelength) to achieve a low take-off angle. Most of your signal goes straight up, which is great for regional chatter but poor for working DX.

By forcing a vertical section of the coax to radiate, the Carolina Windom artificially injects a vertically polarized, low-angle signal into your overall radiation pattern. You get a complex, omnidirectional “blob” of RF that gives you the best of both worlds without needing a massive tower.

Carolina Windom vs. Standard OCFD

Feature	Standard OCFD	Carolina Windom
Primary Radiation	Horizontal (Mostly high-angle on lower bands)	Mixed (Horizontal + Vertical low-angle)
Feedline Route	Can be routed away at an angle	Must drop perfectly vertical for a specified length
Required Chokes	One (At the feedpoint)	One (At the bottom of the vertical drop)
DX Performance	Average (dependent on height)	Superior (due to the vertical element)

Installation Considerations

Because the vertical section is an active part of the antenna, you cannot route the feedline away at an angle or let it lay on a metal roof right out of the balun. The coax must drop straight down from the feedpoint for its designated length before hitting the line isolator. From the isolator onward, you can route the rest of the coax to your radio however you like.