About Transmission Distance Specifications

Author: Randy Owen, President & CEO of ThermoWorks

Transmission distance specifications are a complicated thing. Actual real-life experience with transmitted temperature readings depends on many factors. Normally, the specified “line of sight” transmission range is the “best case” range assuming no physical barriers between the transmitter and the receiver and no interference from other radio signals. It would be impossible to print a specification that covered “normal” home-user conditions because of the infinitely variable circumstances under which a transmitting thermometer might be used.

Differences in home construction and wall composition is a good example. Concrete, masonry, aluminum siding, metal studs, and metal lathe underneath stucco or masonry are all good inhibitors of radio signals. Interference from other radio signals is also variable (microwaves, cell phones, radio communications, networks, etc.), so the only reliable way to compare device specifications is to give a specification for maximum transmission distance under ideal conditions. If you want to evaluate whether a manufacturer actually meets their literal “line of sight” distance claims you should test the device in a rural area with no physical barriers between the transmitter and receiver and little or no interference from other radio signals.

Another option in comparing devices is to look at transmission frequency. 915MHz is normally better than 2.4GHz at penetrating walls and physical barriers.

If you trust the manufacturer, you can normally rely upon a comparison of “line of sight” specs and the transmission frequency for making a relative comparison of products. If the maker has a sterling reputation for specmanship and build-quality, you should be able to rely on their claims for transmission distance as a means of determining which product will have the best range for you, even if in actual use you don’t get the maximum range in their specification.

Remember that the more walls and the greater the radio interference the greater the negative impact on your actual transmission distance. Comparing devices in your actual location is the best way to be assured the signal will work for your conditions.

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