ANTENTOP- 01- 2017, # 021

The Three L-Antennas

Figure 3

Summarizing the Results as the Feedpoint of an L-Antenna is Changed by 0.05 (5%) Increments Around the Center 0.50 ratio

It is clear that an L-Antenna is easy to tune at any up-bend ratio between about 0.35 and 0.65; and with effort, out to a 0.25 or 0.75 ratio.

For hams wishing to fine-tune their L-Antennas, 0.40 and 0.60 are the magic points.

 Note that there is an impedance effect caused by ground coupling as the horizontal arm gets longer. The Wide L-Antenna cannot quite get to a 1:1 SWR.

 Of particular interest is that L-antennas have both vertical and horizontal polarization. The ARRL Antenna Book says:"Some immunity from fading during reception can be had by using two receivers on separate antenna, preferably with different polarizations" (Reference 9).

 In this case there are different polarizations on one antenna. The resulting effect of reduced fading can be heard on DX signals by switching between an L-Antenna and a conventional dipole. For nearby communications, an L-Antenna makes all the difference in hitting repeaters and talking to hams with verticals, dipoles or yagis.

The Tall-L Antenna

When the vertical arm is tall, the length of a 90 degree side arm can be adjusted to resonate the antenna to the desired frequency. The SWR match of a Tall-L antenns can be better than the Equal-L Antenna. Depending on elevation, ground and diameter of the wires or tubes used, there will be some ratio between the length of the vertical and horizontal arms that will give the best match to a 50 ohm coaxial cable. Anywhere up to a 2/3 up-bend ratio works. Understanding this you can easily tune any vertical radiator. The total length will always be about ½ wavelength.

This tall L-configuration has the distinct functions of a vertical in that it is generally quieter than a dipole and performs well for DX. It can be a good choice when listening around the band.

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