In a high frequency product, the antenna plays an essential role:
- A 1/4 wave antenna without its ground plane will behave almost like a wire, whereas if its ground plane is sufficient, its efficiency will be maximum.
- The antenna must always be placed high and clear of any metallic obstacle.
- The antenna cable is another important element that should not be neglected. Ddepending on the type of cable used, the loss will be more or less important [for lengths over 3m it is recommended to use the CFP10 cable (10mm diameter).]
Propagation of radio waves
Radio waves (RF for Radio Frequency) propagate in a straight line in several directions.
The speed of propagation of waves in a vacuum is 3.108 m/s.
In any other environment, the signal is weakened by
- The reflection
- The absorption
Absorption of radio waves
When a radio wave encounters an obstacle, part of its energy is absorbed and transformed into energy, part continues to propagate in an attenuated manner and part may eventually be reflected.
Reflection of radio waves
When a radio wave meets an obstacle, all or part of the wave is reflected, with a loss of power. The reflection is such that the angle of incidence is equal to the angle of reflection.
Properties of the media
|Air||None||Open space, interior courtyard|
|Wood||Low||Door, floor, partition|
|Glass||Low||Non tinted windows|
|Tinted glass||Average||Tinted windows|
Crowds, animals, humans, vegetation
Load-bearing walls, floors, pillars
|Armored glass||High||Bulletproof glass|
Reinforced concrete, mirrors, metal cabinet, elevator shaft
- Check if the power supply is properly connected to the modem
- Check if the modem has been registered to the network
- Check if the radio network coverage is available
- Check if the LEDs are blinking during a transmission
- Check if the meter wires are not reversed and well plugged in the terminal block
- Check if your reading head is well dimensioned for your use (liters, m3)
- Check that the output of your meter does not exceed 5V in the case of a push-pull output
- Check that the power supply is correctly connected to the modem
- Check that "Windows Update" is activated, that the PC is connected to the Internet and that the driver installation is completed. Also check that your version of the configurator is up to date (Menu File -> Update).
- Replace the USB cable
- If the configuration cannot be written, disconnect and reconnect the USB cable
- Check if the power supply is properly connected to the modem
- Configure the modem using the USB configurator
Spread spectrum technology was originally developed for military purposes and is very robust against interference.
We have carried out numerous industrial installations in highly disturbed environments: XI1510 wireless access points next to steel furnaces, overhead cranes, on-board systems, trucks, etc.
This is a point often neglected on many radio equipments: Since the new ABR6 version of the radio card (in 868MHz), we have put a TCXO (Temperature Compensated Quartz Oscillator), which allows to maintain an excellent frequency stability whatever the temperature.
We have applications on ovens for example where one of the radios is at more than 60°C while the other is at room temperature, it is the same configuration on racing motorcycles where the onboard radio modem is at more than 70°C between the exhaust pipes.
Previously without this TCXO, we lost data above 200km/h the Doplet effect making the frequency drift worse, now with the new version the operation remains correct even at high speed.
This indicates that the equipment connected to the ARM-SE is not at the right speed, in fact the ARM-SE supports a rate of 10Mbps max and this happens if it receives frames at 100Mbps for example.
In this case, you just have to set the speed of your equipment to 10Mbps or automatic. On a PC, you have to set the speed of the network card to AUTO.
The Unitelway protocol used on serial links allows communication between a master device and one or more slaves.
The dialogue is always initiated by the master and no slave can decide to speak without the master having given it to him.
The master thus cyclically interrogates each slave in order to assign them a speaking time.
If the slave does not respond to this type of request, the master passes the floor to the next slave after a timeout.
In the case where the communication takes place via a radio link by ARM, it is imperative to increase the timeout set on the master side because of the transmission delays of the radio modems.
As a safety measure, it is advisable to set this parameter to 100ms.
Setup on Windows Vista
Control Panel > Network and Sharing Center > Local Area Connection > Properties > General tab > Internet Protocol (TCP/IP) > Properties > IP address.
If you still cannot access it, check that no firewall ( Control Panel > Firewall ) is blocking the communication and make sure that it is not redirected to another network card (Wifi card for example, which can be deactivated ( Control Panel > Wireless Network Connection ).
Basically, to access the modem's configuration via web pages or to use its radio channel, the machine that connects to it must be configured in the same IP address class.
In the case of a link between two networks of different class, it will be necessary to modify the modem's subnet mask (the modem does not act as a router).
This also has the advantage of filtering a category of IP addresses and not overloading the radio channel, or defining a coverage area associated with a specific class of addresses.
To achieve complete transparency between different or unknown network classes (e.g. Internet) it is possible to set the subnet mask to 0.0.0.0.
Caution: you need a straight SUBD9 cable with all 9 wires connected.
Method for changing the baudrate
- The power supply must be switched off
Connect the HR1200 to the PC with this cable
- Launch the HR1200 software
- Choose the serial port of the PC
- Click on [READ]
- Switch on the power supply and exactly at the same time click on [YES]
- Wait for the end of the reading
- The software displays the radio modem settings
- Go to "Settings for transmission".
- Set the baud rate: 9600
- Click on [OK]
- Switch off the power supply
- Click on [PROGRAM]
- Switch on the power supply and at the same time click on [YES]
- Wait for the end of the programming
- Same for the other radio modem
- You can also change the radio channel in the "Channels" menu (It is advisable to leave the power on "Low" (1W) which is sufficient in most cases and consumes much less
Wi-Fi cannot be deployed everywhere...
Although Wi-Fi waves are less powerful than telephone network waves, they cannot be emitted in all places.
As a precautionary measure, the law on exposure to electromagnetic waves* prohibits the presence of Wi-Fi in places where children are cared for (nurseries or kindergartens) and in elementary school, a device must allow the deactivation of Wi-Fi.
The presence of Wi-Fi must be signaled...
In public areas, the presence of Wi-Fi networks must be posted at the entrance of these areas.
The user must be identified
Leaving one's Internet access open to all users without the possibility to identify them is against the law.
The authorities must be able to know who is using the Wi-Fi, which means that identification systems must be put in place, for example for Wi-Fi access offered to visitors.
The operator must provide electronic data on request...
The French Post and Electronic Communications Code stipulates that the operator offering Wi-Fi must collect certain information, such as the time of connection, duration, etc.
These obligations have been completed by the military programming law and the law on intelligence, introducing new channels of data communication with the authorities in charge of public security. Some data, such as the identity of users, must be kept or transmitted to government services in two cases: judicial requisitions and administrative requests.
And beware. With the tightening of regulations, the lack of response from an operator is no longer acceptable.
"A typical WiFi terminal has a maximum isotropic power of 100 mW.
This is the same order of magnitude as the base station of a domestic wireless phone (DECT), and ten thousand times less than a microwave oven, which uses the same frequency," explains Gilles Dixsaut, head of the new technologies unit at Afsset.
When you are 20 cm from the terminal Wifi, exposure is 0.2 W / m2, one twentieth of the limit value. At 50 cm, we fall to 0.03 W/m2, "well below the limit value of exposure," says Gilles Dixsaut.
"For comparison, a domestic wireless phone base exposes us at least as much to permanent radiation whose frequency is close," he continues. And unlike mobiles, "we know the frequency used by Wi-Fi. It was studied in depth about twenty years ago, for the microwaves.
The site of the AFSSET (French Agency for Environmental and Occupational Health Safety) does not give any information on the dangers of WiFi.