Inverted L Multi Band Antennas
The Inverted L is one of the most effective and practical antennas for getting a strong signal on the low bands when you don’t have the real estate for a full-size vertical or a towering dipole. By bending a quarter-wave monopole so that it runs partially vertical and partially horizontal, you get a highly capable antenna that works exceptionally well for both local NVIS (Near Vertical Incidence Skywave) and DX communications.
How It Works
The Inverted L is essentially an unbalanced quarter-wave antenna. It relies on two distinct sections to radiate your signal:
- The Vertical Section: This is the primary radiating element. It provides low-angle radiation, which is essential for working DX on bands like 160m and 80m. You generally want this section to be as high as physically possible.
- The Horizontal Section: This section acts as “top loading” for the vertical element. While it does radiate at higher angles (which is useful for regional contacts), its main job is to bring the antenna into resonance without requiring massive, heavy loading coils at the base.
Because the highest current point of the antenna is at the feedpoint (the base), keeping the vertical section clear of obstacles ensures the bulk of your RF energy is radiated efficiently, making the most of a 100W signal.
Key insight: The longer the vertical section relative to the horizontal section, the lower your take-off angle will be and better the DX!
Achieving Multiband Operation
A standard Inverted L is cut for a single band (usually a quarter wavelength of the lowest desired frequency). To operate it across multiple bands, you need a matching strategy.
| Method | How it Works | Pros & Cons |
| Remote Base ATU (Recommended) | A wide-range auto-tuner is placed exactly at the feedpoint (the base of the vertical wire). | Pros: Maximum efficiency; tunes almost any band. Cons: Requires running control lines and DC power to the antenna base. |
| Traps | LC (inductor-capacitor) circuits are inserted into the wire to electrically isolate sections for higher bands. | Pros: Can be fed with standard 50-ohm coax; no moving parts. Cons: Traps add weight, reduce overall efficiency, and limit bandwidth. |
| Parallel Wires (Fan) | Multiple inverted L wires of different lengths are connected to a single feedpoint and spread apart. | Pros: Cheap to build; provides resonant operation on multiple bands. Cons: Tuning one wire affects the others; physically difficult to rig cleanly without tangling. |
The Ground System
An Inverted L is only half of the antenna—the ground is the other half. Because the feedpoint impedance of a quarter-wave Inverted L is naturally low (often around 15 to 20 ohms), ground losses can easily consume a massive percentage of your transmit power if the radial system is inadequate.
- Ground-Mounted: You need radials. A lot of them. Laying down 16 to 32 wires (each roughly 1/8 to 1/4 wavelength long) on or just below the grass will drastically improve your radiated signal.
- Elevated Radials: If you can elevate the feedpoint just a few meters off the ground, you can achieve excellent efficiency with only 2 to 4 tuned (resonant) radials per band. This is often the preferred method for homebrewers with limited yard space but some vertical clearance.