Use this tool to calculate how far a UHF radio can transmit.
Enter the antenna height and pick the units (meters or feet).
Formula
d = 4.12 * √h
where h is the antenna height in metres and d is the distance in kilometres.
Example Calculation
For a height of 6 feet, the range of a UHF radio system is 4 miles or 6 km. Note that this assumes no obstructions and no radio interference from other UHF systems. These two impairments would reduce the range.
Background
What is UHF?
UHF (ultra high frequency) is the name for radio frequencies in the range between 300 MHz and 3 GHz (3,000 MHz).
The UHF band is used for various applications including public safety radio systems, land mobile radio communication, amateur radio, and 2-way radio communication.
One of the major applications of the UHF band is in public safety, where it enables efficient and reliable communication for emergency services, law enforcement, and other public safety agencies.
Additionally, the UHF band is utilized for wireless communication services such as cellular networks, Wi-Fi and wireless data networks. UHF television channels are also allocated within this band, providing high-quality television broadcasting. To receive and transmit signals within the UHF band, specialized antennas that are specifically designed for this frequency range are required. These antennas allow for efficient and reliable communication over various distances.
Pros and Cons of UHF
UHF radios, or Ultra High Frequency radios, have their own set of advantages and disadvantages.
Pros
One of the greatest advantages of UHF radios is their small size and portability. Recall that the dimension of an antenna is inversely proportional to the frequency at which it operates. The antennas are therefore easy to carry and install. Similarly the dimensions of electronics components inside a radio decrease with increasing frequency. As a result, the overall size of a UHF radio is smaller than a VHF one.
The UHF band is large (300 MHz to 3 GHz) relative to the VHF band (30 MHz to 300 MHz) for instance. The band therefore comparatively offers a wider range of frequencies and channels, providing
- higher bandwidth and throughput (for example in the 2.4 GHz Wi-Fi bands)
- interference rejection
- enabling multiple voice conversations to occur simultaneously.
UHF radios are better suited for indoor use where long ranges are not as critical as for outdoor applications. Environments such as schools, manufacturing floors, indoor construction, museums, galleries, hospitals, etc. are better suited with UHF radios.
Wi-Fi systems operating in the UHF band at 2.45 GHz have an outdoor range of 6 km or 4 miles. However this is under ideal conditions. For a more realistic estimate of distance with an indoor Wi-Fi network try this calculator.
Cons
One of the main disadvantages of UHF radios is their limited range compared to VHF (Very High Frequency) radios. VHF radios have longer range and signals in this range are not as badly impacted by buildings and trees.
UHF radios require a clear line of sight between the transmitting and receiving antennas, and their range can be affected by buildings, hills, and other obstacles. However, this limitation can be overcome at extra cost by using radio repeaters or by placing the UHF antenna at an elevated location.
References
[1] Line of Sight Propagation on Wikipedia