The Inverted L Antenna

The inverted L is a popular antenna for crystal set users. The analysis was done with EZNEC 3.0, written by Roy Lewellen, W7EL. Go to the link page on this site to get to Roy's page. The Inverted L, T, and Sloping Wire antennas can be analyzed with the free demo verstion. Just be sure to use a limit of 20 segments (the number of pieces that you slice the antenna into for analysis).

This particular inverted L antenna is 75’ in total length, with a 25’ vertical leg and a 50’ horizontal leg. In the plots the vertical section goes up the middle along the Z axis. The horizontal section goes above the Y axis at the 25’ level (points to the right in the plots). Ground losses can change the "gain" and affect the patterns. Nearby objects (such as trees) and sloping ground will affect the patterns, too.

See Figure 1a. The test frequency is 530 kHz. The 3D pattern is donut shaped, slightly squished and smaller toward the positive Y axis, i. e., the pattern is slightly reduced in the direction of the horizontal wire. Maximum gain is 3.28 dbi at 20 degrees elevation in the opposite direction that the horizontal wire is pointing. In the direction of the horizontal wire, the gain is 2.42 dbi at 20 degrees. Figure 1b is the elevation plot.

See Figure 2a. The test frequency is 1700 kHz. The 3D pattern is still donut shaped, but is a bit lossier in the direction of the horizontal leg of the antenna. Maximum gain is 2.68 dbi at 25 degrees elevation in the opposite direction that the horizontal wire is pointing. In the direction of the horizontal wire, the gain is 1.0 dbi at 25 degrees. Figure 2b is the elevation plot.

Figure 1a, inverted L at 530 kHz

Figure 1b, inverted L at 530 kHz, elevation plot

Figure 2a, inverted L at 1700 kHz

Figure 2b, inverted L at 1700 kHz, elevation plot