Ever since the two way radio was invented and available for sale to the public, the burning question that has always been asked has been:
“What sort of range will I get with this?”
Well that question is a lot like “How long is a piece of string?”. It just depends upon a whole lot of different considerations.
And it doesn’t help when you have a raft of websites and product brochures making exaggerated claims about their respective products. This one will say you are guaranteed to get 5 miles, while the other promises 30 miles. Who do you believe? And based on what?
The simple answer to the question of “How far do two way radios work?” depends upon the following 5 issues:
1. Height of the antenna from the earth’s surface
3. Weather factors
4. Power Output
Let’s first introduce the concept of a radio wave. The most important factor to realize is that radio waves travel in what is known as line of sight. The wave or signal must be able to “see” where it is intended to go. Of course we are not talking about being completely free from any obstructions, but the signal has to be able to see its destination in order to reach it.
And if you didn’t realize it, the curvature of the earth and the fact that the earth is round makes a huge difference on the range of radio waves, depending on where you are standing. Without getting into the maths of it, if 2 people were standing on the earth and not impacted by being on a mountain range or in a deep valley, then the maximum range you could hope to expect is about 3 miles.
That’s because once you get past 3 miles, the curvature of the earth causes a loss of line of sight between the 2 users. The radio wave is simply not big enough to make it over the hump of the earth’s surface and hence get’s lost and never reaches the other side.
This also tells you that the higher up you can get, the better chance you have in getting your signal across. It’s not unheard of to get ranges of 25-30 miles if you are transmitting and receiving from different mountain peaks.
The second consideration is obstructions. Radio waves have the ability to pass through the majority of objects, with the exception of metal. They can also bounce off certain substances and also get lost and the signal never be received.
This is where you must take your environment into consideration. If you are using it in forests then depending upon where you are transmitting from, you would experience a higher rate of signal carry than you would if you were using them in a city centre where the size of the buildings and the metal content would play havoc with the reception.
The third consideration is weather. It has been shown that the impact of thunderstorms and lightning can have a impact on radio signals. So be aware if you are heading into a storm that you may get interference or static when using your two-ways until the storm passes.
The fourth consideration is power output. This is where the wattage of the radio can make a huge difference to its range.
The best way to understand this is to realize that a radio signal needs power so it can be pushed into space and reach a receiver.
Now your simple handheld radio may have a power wattage of 1-4 watts. A car radio will have a range of 4-120 watts. So the more watts you have, the further the signal can be carried.
It’s also important at this point to understand the concept of resistance and how it applies. In physics, resistance is the term that’s used when a signal faces an obstacle that either stops it or slows it down. Similar to how friction slows a ball down if its travelling on a concrete path. Eventually it will slow down and stop.
The same thinking can be applied with radio waves, in that radio waves constantly face resistance from the external environment. And here the wattage of the radio can make a major difference on the range, because the higher the watts, the further it can both travel and also pass through any resistance it faces.
This power also comes at a cost, because with handheld radios, the higher the wattage, the greater the drain on the battery which then means the life of the radio can be severely impacted.
The last important consideration is that of frequency. It’s at about this time when people start to get confused because we need to introduce certain terms like VHF (Very High frequency band) and UHF (Ultra High frequency band) into the conversation. And the reason is that depending on what you will be using them for will make the choice of VHF or UHF a very important consideration.
Before we get into specifics, we need to highlight an important fact about the wavelength of a radio signal.
What you need to remember is that the longer the wavelength (a sign of a lower frequency), the further the signal will travel, depending on the wattage required.
Key points of VHF or Very High Frequency band -VHF passes through object better than UHF signals. Less deterioration of signal when it passes through objects
-Require less power to get a VHF signal to travel distance-Do not need a license to use VHF-Better for wider open spaces-More prone to line of sign issues-Battery life in VHF radios is much better than VHF
Key points of UHF or Ultra High Frequency band
-UHF has a smaller wavelength so is better in smaller, confined spaces-Uses more power to transmit radio signals-Require a license to use UHF band
In summary, from what you would expect to be a simple question is in fact one that requires you to place a lot of thought and consideration into the exact reasons for why you need your two way radios. And if you take the time to consider the above key points, you will go a long way towards getting the best range out of your radio for your specific needs.