Wireless Antenna Selection and Etiquette

December 6, 2017 by Ben Stowe, CTS

One of the challenges with reliable wireless signal transmission is that it’s invisible, so it’s difficult to see issues. Even solid, quality radios can be handicapped by poor antenna selection or placement.

One critically key element is to provide a line of sight connection between your transmitting and receiving antennas whenever possible. Basically, you should have a clear path between those antennas as much as possible. Two things that dramatically affect radio waves are metal and water. People don’t like it when point this out, but we are essentially giant walking bags of water. It varies from person to person, but on average we are 60% water by weight. Try to limit the number of people and metal surfaces between your antennas.

Also, it’s important to choose the best antenna for the job. Most wireless systems ship with ¼ wave antennas (about 6” in length for a UHF system). These are monopoles, and as such require the ground plane from the receiver chassis. The most important take-away from this is that these antennas should not be remotely mounted, which means achieving line-of-sight can be harder.

A larger “stick” shaped antenna, called a ½ wave dipole can be used and this provides a couple meaningful benefits. The first of which is that they can be remotely mounted and do not have to be attached to the receiver’s ground plane. The second is that they have greater antenna gain and provide a stronger signal from the radiated energy of the transmitter.

Even better yet is a directional antenna, called a Log Periodic (LPA), sometimes also referred to as a shark fin or batwing antenna. These are made up of an array of antennas on a solid surface that increases antenna gain in one direction, while not another. This allows us to focus our reception towards our transmitter while reducing the likelihood of interference from areas we don’t’ need coverage. These can be mounted on stands to get them up high to provide excellent line-of-sight also.

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