What is this LoRa technology?
Transmitting measurement data in an uncomplicated manner and from anywhere if possible - that is the idea behind the Internet of Things (IOT). This requires radio technology with good range and low power consumption. These two features are the core idea behind LoRa technology or LoRaWAN networks.
LoRa stands for Long Range and initially refers only to a special type of modulation for radio signals. This modulation has the benefit to achieve large ranges at low power, even penetrating buildings. However, the amount of data is very limited, only very low speeds are available. This is therefore not a technology for voice or video transmission. But for machine data such as filling levels of containers, soil moisture or temperature, we only need a few bytes of data per measurement. For such signals a low speed and also a high latency are not problematic.
From LoRa to LoRaWAN
The LoRa signal always originates from a sensor. The next element in the chain – the gateway - then relays the data to a larger network. A gateway can be as simple as a receiver that covers a certain region. The gateway forwards the data received by LoRa radio via a network (LTE, WLAN, Ethernet...) to a server, where the operator of the sensor can then retrieve and evaluate it. This entire infrastructure of sensor (also called 'node'), gateways and one or more servers is called LoRaWAN, i.e. Long Range Wide Area Network. There are several operators of LoRaWAN networks, some of which serve closed user groups, but some of which are open to everyone. Examples are "The Things Network (TTN)" or "The Peoples Network" (aka Helium, more on this below). Other operators are some of the well-known mobile phone providers. If you only want to cover a small area of your own, you can also set up the entire infrastructure privately. In this case, you do not have to rely on a provider.
Antennas improve the range
LoRaWAN technology currently uses only the licence-free frequency range at 868 MHz. As with any radio technology, you can drastically increase the range with the right antennas and suitable accessories such as good cables. That is what WiMo is all about – providing solutions for a good range with the right antennas.
The antenna on the sensor
On the sensor, you are limited with what you can do with the antenna. Usually omnidirectional antennas are the simplest solution, because the direction to the next gateway is unknown. However, you can always use a better omnidirectional antenna and attach it with a cable in a position with better radiation properties.
The antenna on the gateway
Since the general LoRaWAN technology and the widespread Helium network do not differ in this respect, here are our tips for the Helium network. However, they generally apply to all LoRaWAN networks on 868 MHz.
Which antenna is best for Helium?
As always - it depends. However, it is not complicated at all.
If you want to cover the whole area around your location, place the antenna at an unobstructed location, if possible. In this situation, a normal omnidirectional antenna is probably the best choice. Not too high, a little away from the wall, the roof or other massive structures such as walls or air-conditioning units. It is also important that the antenna has a clear view of the area to be illuminated. You can check this, for example, here https://explorer.helium.com.
A Specific Area
If you want to cover only a certain area, for example because you live on the edge of a village, a directional antenna is a good choice. It is important to remember that the back of the antenna emits almost no signal. Do not expect to pick up any sensor signals from the back of your directional antenna, at least not beyond a distance of a few meters. On the other hand, the signal is better and reaches farther towards the front, in the direction of the target area.
What gain should an antenna for helium have?
First of all, some fundamentals: An antenna does not work miracles, it is not a 'perpetuum mobile', it does not generate energy from nothing. An antenna takes the provided energy from the cable and radiates it as completely as possible. The simplest antenna in the world, a perfect omnidirectional antenna, radiates evenly in all directions, in the shape of a sphere. Such an antenna would have '0 dBi' gain. All other antennas with gain > 0 dB deform the radiation field and concentrate the energy in a certain direction, nothing more. How much stronger the measurable energy is in this preferred direction is indicated by the gain of an antenna. The gain of an antenna just says that the signal in the preferred direction is stronger by a certain factor in comparison to the perfect omnidirectional antenna.
A simple comparison: A candle radiates weakly but in all directions, a lighthouse also radiates all around in all directions, but not upwards or downwards. For this, the light is all the brighter exactly in the plane of the lighthouse's light source.
An omnidirectional antenna with gain deforms the spherical field more in the direction of a 'donut', i.e. into a strongly flattened sphere. The more gain, the flatter this shape becomes. Too flat (too much gain) is not good either, because the radiation field can become very flat and, if the antenna is placed in an elevated location, you may be radiating over the heads of the receivers. In this case, distant antennas will receive the signal better; they just have to be at the same height. So if this is your intention – fine.
A simple comparison: The candle radiates everywhere, the car headlight only in a cone-shaped area and only a little up and down.
A directional antenna with gain deforms the field in both the vertical and horizontal directions. In other words - the directivity results from bundling the field in a certain direction. The higher the gain of an antenna, the stronger the bundling. But beware - this means that too much gain can be counterproductive. A directional antenna with extremely high gain has a pencil-thin directional beam, which can easily reach a distance of 10 km. Such systems are used everywhere, but only in point-to-point links for networks. That is not what we need. After all, Helium is supposed to supply an area, not a single, distant point. Sector antennas are a good choice in many cases. They have a wide but fairly flat field, ideal for large areas.
Now let's get down to business: How much gain should an antenna for helium really have?
with large height difference to its counterpart (church tower, mast)
with little height difference to its counterpart (Small mast in the garden, at the side of the house)
in various heights
Which installation height is best for a Helium antenna?
That is a question of geometry. In any case, it should be high enough to prevent thieves from accessing the antenna or cables. 3 m above the ground would be the minimum height. You can also mount an antenna in the light well of the cellar window, but then it will hardly reach beyond your own garden.
Mount an omnidirectional antenna with moderate gain at a higher elevation if you can find a suitable place for it. The details always depend on the terrain, so it is difficult to give general suggestions. Check where your 'customers' are located, i.e. the sensors and the other gateways that I want to witness in the Helium network.
If there is only one location available at high altitude and a you want to use a directional antenna, it may have to be tilted downwards in order to cover the desired region with its radiation.
The fine art of antenna construction starts when one wants to join several directional antennas, for example to reach separate areas with only one gateway. Here you can combine antennas quite easily with a distributor (a so-called splitter or 3dB divider). There are a few rules to follow, and our antenna specialists will be happy to advise you on these.
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LoRa Helium Antenna Set #1 - Omni
The perfect set for a Helium/LoRa omnidirectional antenna - everything included! Antenna, wall mount, cable. Ideal for open areas or streets where the antenna can be placed in the middle at a height of a few metres.
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LoRa Helium Antenna Set 2 - circular polarisation
Want to illuminate a specific spot at a greater distance? No problem - with this bundle it works perfectly. Everything is included - antenna, wall mount and cable for Lora/Helium gateways.
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LoRa Helium Antenna Set #3 - linear polarisation
Linear polarisation, ideal for the open field. You can also use it to illuminate a specific corner at a greater distance. Everything included - antenna, wall mount and cable for Lora/Helium gateways.
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