This article explains how to optimize the range of your remote control. Tyro Remotes is happy to explain about what can negatively affect radio waves in turn influencing the range of our system and provide you with some suggestions for getting the best results out of your setup.
- What determines the range of my remote control system?
- What influences radio waves?
- How can I optimize the range?
- 433 MHz or 868 MHz or 2.4 GigaHerz? Narrowband or Broadband?
- Testing and verification
Good to know:
- The maximum indicated range is always an indication based on a measurement with line-of-sight without interference. The range cannot be guaranteed as this is always subject to various environmental factors.
- The illustrations have been added as an indication and do not give an exact representation of the reality.
1. What determines the range of my remote control?
The range of radio frequency (RF) systems can be limited by factors such as shielding, reflection and shadowing. Interference sources present between the transmitter and the receiver have an unpredictable influence on the range. If there is a line of sight between the transmitter and the receiver, there is a high chance of optimal range, but it is still not 100% sure that signals will arrive.
Radio waves have only limited strength, which decreases after a short distance. The decrease in the energy of the radio waves is inversely proportional to the square of the distance. In addition to external factors, frequency and bandwidth also affect the range of the remote control.
Four factors that determine the range
If we disregard absorptions and reflections for a moment, there are four factors that determine the range of radio frequency (RF) communication systems.
- The power of the transmitter
- The sensitivity of the receiver
- The antenna gain factor
- Attenuation of the radio signal (by air or obstacles)
The transmission power of the transmitter and the reception sensitivity are two factors that determine the range. The receiver requires a minimum level signal to isolate (demodulate) the source signal from the signal to be received. To achieve this, a high transmit power is ofcourse advantageous.
The above four factors are summarized as the link margin. The link margin adds transmit power and gain by antenna and subtracts reception sensitivity and attenuation.
|Link Margin =||+ Transmitted power|
|– Receiver sensitivity|
|+ Amplification by the antennas|
|– Attenuation of the radio signal|
|Link Margin =||+ Transmitted power|
|– Receiver sensitivity|
|+ Amplification by the antennas|
|– Attenuation of the radio signal|
If the power of the transmitter (TX) – the sensitivity of the receiver (RX) is greater than the signal attenuation, this means a positive link margin, and thus radio communication is possible.
The type of material determines how the radio waves are affected. The damping can vary enormously per material. A plastic housing or control box hardly absorbs any signals. The antenna can even be mounted inside the cabinet. On the other hand, a reinforced concrete wall of 20 centimeters’ thickness does not transmit any RF signals.
The most difficult obstacle for radio signals is metal. Metal reflects the signals and does not let anything through. That is why we recommend that the receiver, or at least the antenna, should be mounted outside the cabinet when using a metal switch box.
Interference sources are not always visible (e.g. humidity or electric fields). Depending on the interference sources in your area, the choice of the correct frequency and / or modulation can also have an effect on the range of your RF system. You can find more information about this in strong>chapter 4. 433 MHz or 868 MHz?.
Take reflections into account
In addition to damping, reflection of radio signal also requires attention. Reflections can contribute negatively and positively. It is almost never the case that a signal goes directly from the transmitter to the receiver without being reflected anywhere; not even if there is “visual connection” without any obstacles.
The signal from a transmitter antenna spreads like a donut. It is reflected from the ground and arrives at the receiving antenna. Between buildings, the signal also reflects through the facades. If there is a building or steel wall between transmitter and receiver, the signal will use these reflections. Through reflections on surrounding structures, it can reach the receiver without a visual connection. Keep in mind that the signals do get first muted before they are reflected.
Our ‘Safe’ systems are equipped with an out-of-range function. The receiver switches off when it no longer receives a continuous signal from the transmitter. This means that in practice, the range of these systems is often less than systems without this function.
2. What influences radio waves?
How strongly the signal is affected depends on various environmental variables. There is a large number of interference sources that negatively affects the range of RF systems.
The most common sources of interference are:
- rain / snow
- electric fields (eg transformers, motors, light poles)
- other RF systems
On its way from the transmitter to the receiver, radio waves may have to deal with various influences. A radio frequency signal can:
- change directions
- increase in strength
In contrast to light, for example, it is possible for radio waves to penetrate to solid material. The mentioned sources of interference do attenuate or absorb a signal, but in most cases it does not resolve completely. The amount of energy lost is highly dependent on the nature and density of the material.
A radio signal can resolve if the signals have not been able to reach the receiver because the distance is too large. Signals can also dissolve when they are absorbed or as a result of the composition of the outside air.
To change direction
Radio waves can also change direction, or reflect. Reflection occurs with all products that contain metals such as mirrors, metal door frames, metal cabinets and construction steel. Insulating glass or insulation incorporating metal foils also reflects radio waves.
Reflective material causes a “dead spot” with only a few very small radio waves or without radio waves. This is also known as radio wave shadow. The power of the signal can therefore be greatly weakened or fully reflected.
Water surface reacts almost the same as metal. That is why it is highly advisable to test the range over water, from ships or at locks, in advance.
Good to know:
- Steel plating almost always has a bad influence on the range. If the receiving antenna is mounted close to steel sheeting, the range can even be minimized. Also, when mounted in a metal container or cage, it may happen that, contrary to the specifications, the systems cannot be operated simultaneously. This is because the reflections cause interference. In this extreme environment, for RF signals, it is not possible to work side by side simultaneously. Timely testing prior to final assembly is not only advisable in such an environment, but really necessary.
Increase in strength
If two signals (from the same source or from two different sources) come together, they could amplify each other. However, the signals can also weaken each other.
3. How to optimize the range?
In addition to the correctly selected remote control and the prevention of interference sources, the location of the receiver and antenna is very important for the range. Therefore, keep the following points in mind to optimize the range of your system:
- In case of multiple receivers, place them at least 50 cm apart.
- Never place the receiver or antenna directly against or on a metal object, at least 50 cm away from it.
- Mount the receiver or antenna a maximum of 3 to 4 metres above the working level; higher or lower than the working level reduces the range.
- Place the receiver at least 50 cm away from motors or other equipment capable of generating a force field.
- Never place the receiver with antenna in a control cabinet, cabin or similar (metal) housing.
- If the receiver has to be placed unfavourably, the antenna can usually be mounted in a different location by means of an antenna extension cable.
- If possible, ensure that there is a line-of-sight connection to the receiver during operation. (check picture 6).
- In applications where work is carried out at the same height, such as winches or shaft control, it is best to mount the receiver and antenna vertically.
- In applications with large differences in height, such as in elevator technology, it is sometimes better to mount the receiver with the antenna positioned horizontally.
Positioning of the transmitter and receiver
Position transmitter: In general, the hand-held transmitter should be positioned vertically in order to have as wide a range as possible. This also depends on the antenna position of the transmitter in the housing.
Receiver antenna position: Always position the receiver vertically unless the receiver is far above you, in which case it may be better to position the antenna horizontally.
Example: Many users place a receiver with a vertical antenna high up in the ridge of a production hall, preferably right above the machine to be operated. The reasoning is as follows: there is always a visual connection to the hand-held transmitter. However, this will not have a positive effect. If you draw the signal around the transmitter and receiver antenna like a donut, you will see that the range is not good everywhere. The transmitter cannot reach the receiver on the ground where you normally walk and work. The advice is therefore, to place the receiver at a height of 2 meters or to place the antenna horizontally.
Devices on the same frequency
Make sure that no wireless equipment is operating on the same frequency in the vicinity of the receiver; this may adversely affect the operation and range of the system.
Extreme sources of interference
Because radio signals are affected by electromagnetic fields, we recommend shielding or remotely placing transmitters and receivers. Think of frequency converters, inverters, transformers, light poles and household equipment such as a microwave.
There are two basic types of antennas:
- the receiving antenna that receives radio frequency energy and converts it into an alternating current.
- the transmitting antenna that is supplied with an alternating current and converts it into a radio frequency field.
In its simplest form, an antenna is a conductive thin wire. The antenna uses the phenomenon that electromagnetic waves in conductors generate an alternating current (when receiving) and vice versa that alternating current generates (transmitting) electromagnetic waves.
The length of the antenna depends on the desired frequency range. With the 433 MHz frequency this is 16.5 centimeters (from the base) and with the 868 MHz frequency this is 8.2 centimeters (from the base) or 13.5 cm (SMA). In principle, there are no differences between a transmitting and receiving antenna. The length of the antenna does not determine the range of the remote control.
A good and undisturbed operation of the antenna is of essential importance for the range of the radio signal. Things such as corrosion of the wire or a connector, cable breakage or incorrect antenna placement have an immediate negative effect on the range.
Installing the antenna at control cabinets
If you are installing a receiver in a control cabinet, we recommend that you mount the antenna outside via an antenna extension cable with the coupling piece. A metal control box works like a Faraday cage, so no signal penetrates. However, an extension cable also has a certain attenuation. That’s why it always applies: as long as necessary, but as short as possible.
Antenna mounting on a steel surface
If a steel surface is applied underneath the antenna, this will benefit the antenna performance. It has been shown that for a monopole antenna vertically on the ground plate acts as a surface to reflect radio waves. To function properly, the antenna ground plate (conductive surface) must be at least the size of one quarter of a wavelength (calculated from the base of the antenna).
4. 433 MHz, 868 MHz or 2.4 GigaHerz? Narrowband or Broadband??
433 MHz vs 868 MHz
Because many different types of equipment are allowed on the 433 MHz frequency band, this frequency is more sensitive to interference than the 868 MHz frequency band.
As for the transmission of signals with longer wavelengths, they generally cover a greater distance and have better permeability than signals with shorter wavelengths. Higher frequencies result in shorter wavelengths. Technically, 433 MHz can cover a greater distance than 868 MHz. However, 433 MHz and 868 MHz can have the same radio frequency (RF) -transmission performance, because there are many other factors that determine this performance.
In the “Open Field”, there is technically no difference in the range of 433 MHz versus the 868 MHz frequency band. However, the 433 MHz frequency band suffers less reflections and has better permeability.
Bandwidth – narrowband vs broadband
In radio communication, the band is referred to as the range of frequencies (bandwidth) used in the channel in question. Depending on the size of the band (in terms of kHz, MHz or Ghz) and some other properties, they can be categorised as narrowband or broadband.
Broadband communication uses – as the name indicates – a wider part of the spectrum. This has some advantages and disadvantages:
Broadband communication provides a higher bandwidth and therefore faster communication. This communication makes it possible to filter out narrow noise sources in the spectrum. It is more difficult to transmit and detect broadband signals; it requires a high signal-to-noise ratio. The energy of the signal is distributed over the width of the spectrum, making the signal weaker as it widens (assuming a certain power level).
Narrowband communication uses a narrow bandwidth. These signals are often used in a slower form of communication where mainly voice or slow data streams need to be transmitted. Narrowband signals usually have a much wider reception range because narrower filters can be used and therefore eliminate unwanted broadband noise. The transmitted energy also concentrates on a smaller part of the spectrum. Narrowband technology is used for a good connection at a longer distance or in disruptive conditions (e.g. a metal rich environment).
The world is full of remotely controlled equipment operating at 2.4 GHz. That seems convenient, because the 2.4 GHz can be used anywhere in the world. Moreover, it is the only radio free bandwidth that can be used in all countries worldwide.
This bandwidth is very popular and is used for many (mostly non-professional) applications such as modelling for boats, cars and planes and for drones and WiFi routers.
LBT and AFA
Various narrowband systems use LBT / AFA (“Listen Before Talk” / “Adaptive Frequency Agility”) technology. With these techniques we first check if the channel is free. If this is the case, the connection is set up on this channel. If this is not the case, the next channel is selected.
5. Testing and verification
All our systems have been developed to have an optimal range under normal circumstances.
As described, there are quite a few external influences that can influence this range both positively and negatively. Therefore, in situations where reflections, damping or external sources of interference are present, we recommend that you first test whether the range is sufficient for your application in these cases or not.