One of the most common two way radio questions suppliers receive is, 'how far can two way radios communicate?' This is not an entirely simple question to answer as there are so many variables that can disrupt or affect the communication distance.
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Two Way Radio Power Output
It is always beneficial to understand the differences between licence free and licenced radios. The power output of handheld radios ranges from 0.5 watts (licence free) to 5 watts (licenced). Fixed mobile two-way radios such as those found in vehicles usually have a power output of between 25 and 45 watts. The more power your radio has the further it will transmit.
Two Way Radio Frequencies
There are two main frequencies used, which are radio and Very High Frequency (VHF) and Ultra High Frequency (UHF). There are pros and cons to both frequencies and selecting the correct one will depend on your application. But to understand, how far can two way radios communicate, we need to know a little bit more about these frequencies.
Very High Frequency (VHF)
VHF frequency waves are wider than UHF and are often used where the distance to be covered is further and more open with few buildings.
Ultra-High Frequency (UHF)
VHF frequency waves are narrower than UHF and are often used in built-up areas, where the distance to be covered is less but with buildings to transmit through.
Detrimental Factors to a Two Way Radio Signal
Two way radio signals can penetrate through plasterboard, humans, furniture, masonry, wall panelling, and other solid objects but all these objects will reduce the signal strength. The radio signal requires a line of sight to the receiving radio therefore it is worth noting that the radio signal cannot pass through the earth.
Tunnels are another area where two way radio signals suffer. If you are planning to use two way radios in a tunnel you will need need to consult a specialist company. They will be able to help provide a site survey and discuss the infrastructure required, such as leaky-feeder cabling.
Licence-Free Two Way Radios
You may have seen manufacturers claiming that a licence-free radio with a power output of 0.5 watts, using UHF frequency, can transmit over a distance of 10 kilometres. While this information is correct, based on how they tested the two way radios, it does not give a real-world communication distance or given an answer to the question, how far can two way radios communicate?. The tests are often performed in perfect atmospheric conditions from a valley hilltop to a valley hilltop 10 kilometres away in the perfect line of sight. Naturally, if you are operating in this type of environment then the distance stated will be of use. More often than not these two way radios are used at ground level, in and around small buildings. Because buildings affect the distance of the two way radio signal you may find that 10 kilometres may be reduced to 500 meters or less.
The only way to determine how far the two way radios that you would like to use will transmit in your given area of use, is to test them.
Licenced Two Way Radios
Handheld two way radios come with maximum power outputs of 5watts for VHF and 4 watts for UHF. Fixed-mobile two way radios have maximum power outputs of between 25 watts and 45 watts depending on the model you purchase. Licenced radio equipment will need an Ofcom radio licence to legally operate in the UK.
The distance that these two way radios can cover will be dependent on all of the factors discussed above. It should be possible over flat open ground, using handheld licence two way radios, within line of sight to get 3km and up to 1km in a built-up area. If there are any obstructions or the area is heavily built up, such as in London these distances can be reduced further. Therefore, we always recommend contacting a two way radio supplier for them to come and provide a site visit.
Repeater Base Stations
If you are looking to increase the distance that licenced two way radios can cover, you can always add a repeat base station. The repeated base receives the two-way radio signal and re-transmits the signal through a strategically placed antenna.
Repeated base stations are used on large sites, sites with basements, and general sites with hard-to-reach areas of use.
Although not as common as in the past there are still many aerial masts available to use and are largely found on high ground. Traditionally used by taxi companies, and councils although they can be used by anyone requiring to have two-way radios cover the area they provide.
As you will realise from reading the above text, there isn't a simple method of determining the question; how far can two way radios communicate? We can only advise, either purchasing and testing a pair of two-way radios in the intended area of use or contacting a a two-way radio supplier for support.