Do you know the secret about Watts in your PMR radio? (Nobody else will tell you)
Do you believe that a more powerful PMR radio enjoys better coverage? If so, think again.
Many people have the wrong idea about how powerful their PMR radios need to be. Sure, walkie-talkies need high power to transmit and receive signals between radios, because they operate without a network.
But PMR radios are completely different. They use a powerful network to communicate so they don’t need a high output power to get through to each other directly. The only exception is if they are switched to Direct Mode (DMO).
Ah, you say, vehicle radios are more powerful and they enjoy better coverage. Yes, it’s true, mobile radios do have more output power - but that’s not why they get service in places where handhelds struggle. That’s mainly because vehicle radios have a long antenna that is in just the right place. It also helps that signals are not blocked by the user’s body, which can seriously affect handheld radios.
Some base stations are just good listeners
PMR radios and base stations communicate back and forth with each other. A good, sensitive base station, such as the TB3-series TETRA base station, listens well, especially when equipped with the recommended antenna solution. TB3-series base stations can “hear” radios transmitting with lower power.
That’s important because the less power that a radio uses, the longer its battery will last. It can make a critical difference to professionals in the field who don’t want to be let down by a flat battery when they most need their radio.
On balance, 1 W is enough
The radio network should have a balanced uplink and downlink - there is no point in one being stronger than the other. A TETRA radio network, for example, often uses base stations transmitting at 25 W. To find the radio’s optimal output power we need to know the sensitivity figures of both the radio terminal and the base station.
Let’s say the radio has -105 dBm sensitivity and the base station has -112 dBm sensitivity. It turns out that a typical 25 W base station, with diversity and panel antennas for uplink, requires the device to transmit at 1 W. This guarantees maximum coverage.
Any more power in the radio brings no benefit, except if the radio is used in DMO.
So beware of claims that you need very powerful PMR radios to get the coverage you need. It’s not true and can actually degrade your operational efficiency.
Don’t worry about power – your radios will have all they need.
Check this infographic which explains the truth about Watts in PMR radios - or download the same infographic in printable format:
You can also download the infographic in printable format:
Here's the same infographic in French: "La vérité sur les Watts des radios PMR"
You may also be interested in another blog post which deciphers the IP classification ratings of PMR radios: Do you have this wrong idea about IP protection ratings?