Beware Range Reduction – Audio Accessories and Low-Profile Antennas.

Two way radio users have many different accessories at their disposal to enhance the system functionality. Speaker microphones, lapel microphones, and low profile – or stubby – antennas are an appealing option for many. When used properly, both accessory types can enhance the usability and functionality of a two way radio system. But, like most things in life, that enhancement comes at a cost – usable radio range. The use of low profile antennas and audio accessories must be taken into account at the outset of a system design to ensure adequate signal in present and can overcome the attenuation introduced by the involved accessories. When you perform your live coverage test before you purchase – you do test the proposed radio system before you initially buy it, right?? – make sure your test mimics how the radios will be used when deployed.

What affects radio range?

Radio waves are part of the electromagnetic spectrum, just like visible light. And just like visible light, certain materials allow the wave to pass relatively unimpeded (clear glass), certain materials diminish the intensity of the wave (waxed paper) and certain materials block the wave altogether (cardboard). How a material affects the wave is based on the molecular structure of the material and the frequency/wavelength of the wave. That simply means that not all waves are affected in the same way by the same material. For example, a piece of cardboard will block all visible light from passing though, but has relatively no affect on radio signals. Conversely, some energy efficient windows utilize a metallic coating that only slightly affects visible light, but has a severe attenuating affect on radio signals.

How do audio accessories affect the radio waves?

One of the primary purposes of an audio accessory, or at least a major result of their use, is that the two way radio is kept on the user’s belt. The human body presents a very large impediment to radio signals. At low levels, it is not dangerous, it just simply absorbs the radio signal. In many cases, the reduction can be 1, 2 even 3 orders of magnitude (10x, 100x, 1000x). That can really shrink the range of your radio communications. Additionally, the antennas on the two way radios are designed to be in free space, with no objects directly touching them. The effect of an object (like your waist) touching the antenna is that the antenna becomes detuned – or less efficient at the desired frequency. This all adds up to reduced range.

How do low-profile or stubby antennas affect range?

This can get a little heady, but here goes… All radio antennas’ dimensions are related to the frequency or frequencies, at which, the antenna is designed to radiate. Antennas, again, are a compromise. They’re good at a wide range of frequencies, but not great at any one frequency – at least any one frequency of consequence to the end user. The most common two way radio antenna is the 1/4-wave whip. Other antennas employ different polarizations or loading techniques reduce antenna height (but not width) or to “fool” the radio’s transmitter into see the proper loading. Just like a car engine, if there is no load attached to a two way radio, bad things can happen. Just because these low-profile antennas have fooled the transmitter into seeing the right load, it doesn’t mean the signal isn’t negatively affected. You can put a car on a dyno, but you ain’t goin’ anywhere.

Ultimately, the affect of low profile antennas is less than keeping a radio on your hip. Signals may be reduced by 2-times to maybe 10-times.

What can be done?

In some cases, moving to digital modulation (NXDN, DMR, P25) can provide the necessary “oomph” to make up for the shortcomings of losses introduced by these accessories.

The best course of action is to make sure you test your proposed radio system before you buy it. In most cases, a very similar radio system can be temporarily set up at your facility to provide a proof of concept. During that test, use stubby antennas and audio accessories if you plan on using those accessories now or in the future. As the radio system matures and new people come into the purchasing fray, the prospect of using these accessories is appealing, to the new folks, but nobody has every talked to them about the potential drawbacks of these accessories. Remember to plan for the future.

In almost any case, Viking Communications can provide you with a proof of concept system that will ensure your final system provides you with the coverage you need and expect.

CONTACT VIKING COMMUNICATIONS!

We have demonstration equipment available for our products and services and are very excited to meet with you and your team to see how we can improve your organization. Contact Viking Communications, we have been in the business since 1964, always maintaining the consistent goal of helping our clients to communicate more effectively and efficiently. We are locally owned and operated, this allows us to provide professional service in two-way communications systems, with a personal approach for each client.

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