Two way radios are essential pieces of equipment for busy, dangerous building sites, and choosing radios that are fit for purpose is vital for safe and effective communications. One very important choice to make is whether to go for Very High Frequency (VHF) or Ultra High Frequency (UHF) radios, as the frequency band you and your colleagues use can dramatically affect the performance of your radios.
What are the advantages and disadvantages of using VHF radios?
VHF radios have advantages over UHF radios that can be particularly useful for construction work:
- Range: As the names would suggest, VHF radios operate on lower frequencies than UHF units. Since (as a general rule) lower frequencies travel further than higher frequencies before terminal signal degradation, VHF radios can have significantly longer ranges than their UHF counterparts, a great boon on large industrial and commercial building sites. This range can be extended further with the use of static antennas.
- Battery life: VHF radios tend to use less power than UHF equivalents, useful for isolated sites where finding power points for battery charging can be difficult.
However, using VHF also comes with a few disadvantages:
- Signal loss: VHF signals are more badly affected by obstructions than UHF signals, and any solid object from a concrete wall to a human body can cause signal problems. As such, VHF may not be suitable for infrastructure-heavy building sites, particularly when workers are communicating over several storeys.
- Limited channels: Available VHF channels can be limited, particularly in urban areas. While this can make finding open channels difficult, it can also lead to another problem:
- Interference: Because of this channel limitation, signals operating on slightly different frequencies can often overlap to cause unacceptable distortion. The long range of VHF radios means that interference can come from mysterious sources miles away, so tackling the issue can be problematic.
What are the advantages and disadvantages of choosing UHF radios?
UHF radios boast a number of features that their VHF counterparts lack:
- Signal strength: The short wavelength of UHF signals mean they can pass through solid objects relatively easily, and can propagate through small gaps in walls and other structures. This makes them much more useful for crowded building sites and multi-storey projects, or sites with particularly rugged and uneven terrain.
- Low interference: Many more channels are available to UHF users than VHF users, allowing plenty of 'space' to keep channels from overlapping. UHF radios are also less susceptible to static interference caused by electrical equipment and generators.
- Compact size: High frequencies and short wavelengths mean that portable UHF radios do not require large antennas to function; as such they are generally small and compact, with less chance of antenna breakage.
There are, however, also distinct drawbacks to using UHF two ways:
- Licensing: Depending on the power of your UHF radios and the length of time they will be used, you may need to apply for a license from the Australian Communications and Media Authority before they can be used legally -- these licenses can be expensive, particularly for large-scale sites requiring powerful UHF transmitters.
- Distortion: While UHF radios are not as vulnerable to interference as VHF models, signal distortion can still take place -- the short wavelength of UHF carrier waves means that they can be reflected by certain surfaces and objects in unpredictable patterns. This can cause conversations to become notably out of sync over time, and may lead to signal duplication and other forms of distortion.