What Is a Wireless Communication Modem? Types and Selection Criteria
A wireless communication modem carries a control signal or serial data between points where cable cannot be run, over the GSM network or an RF/LoRa radio link.
A wireless communication modem is a device that carries a control signal or serial communication data between points where cable cannot be run, over the GSM network or an RF or LoRa radio link. It is used for pump control between a well and a tank, for reading remote meters and analyzers, and for connecting RS-485 devices spread over a site to a central system.
Types
| Type | How it communicates | When to use |
|---|---|---|
| GSM well-tank set | Transmitter and receiver over the operator network | When the points are far apart or the terrain between them is rough; both points need coverage and a SIM line |
| RF well-tank set | Transmitter and receiver over a direct radio link | When the distance is within the product's range; no SIM and no line fee |
| 4G GSM modem | Over the cellular network | To reach a device on site from a central or remote location |
| Wireless serial converter (RF, LoRa) | Carries a serial line over radio between at least two paired devices | To link two RS-485 points where cable cannot be run |
Well-tank sets usually carry the state of the level switch in the tank, that is the float switch, to the pump control at the well; check the wiring diagram in the product manual.
Selection criteria
- Communication path: If there is a clear line of sight between the two points and the distance is within range, RF or LoRa works without running costs. If the distance is long, or there are hills or buildings in between, choose GSM; check operator coverage at the installation point with a phone beforehand.
- Range: The product data includes models rated for transmission distances of up to 5 km and up to 10 km. Actual range depends on terrain, buildings, trees and antenna placement; mount the antenna high and clear of obstacles.
- Serial interface: The converter's interface must match the device it connects to. The G-LORA-485-D10 is for RS-485; the product data for the G-9921 gives RS-232, RS-485 and RS-422 options. Baud rate, data bits and parity must be set the same at both ends.
- Number of devices: RF and LoRa converters do not work alone; each link needs at least two paired devices. Well-tank sets come with the transmitter and receiver together.
- Antenna: A modem enclosed in a metal panel loses signal. Bring an external antenna outside the panel and check that the antenna connector matches the modem.
Common mistakes
- Treating an RF or LoRa converter as a GSM modem: These devices use no SIM card and do not connect to the operator network or the internet; they communicate only with their paired device.
- Installing a GSM set without checking coverage: Wells are often far from settlements; with weak coverage, control is delayed or lost.
- Leaving the antenna inside the panel: The metal enclosure blocks the signal and range drops noticeably.
- Expecting the catalog range over rough terrain: The stated distance is for open ground; with hills and buildings in between, the range is shorter.
Wireless communication modems in the catalog
The Wireless Communication Modems category has 5 active products: Tense 3, GMT 2.
| Model | Brand | Type |
|---|---|---|
| GSM-MOD-SET | Tense | GSM well-tank communication set |
| RF-MOD-SET | Tense | RF well-tank communication set |
| GSM-MOD-4G | Tense | 4G GSM modem |
| G-9921 | GMT | Wireless communication converter |
| G-LORA-485-D10 | GMT | LoRa RS-485 wireless communication converter |
External antennas for mounting outside the panel are in the Communication Antennas category: the Tense HA-5 (5 dBi) and HA-9 (9 dBi); the GMT 4G and Wi-Fi antennas in the category are for GMT HMI panels, so check connector compatibility on the product page before fitting them to a modem. Where wired Ethernet reaches the site, the Tense ETH-GTW Ethernet modems that connect an RS-485 line to the network are in the Industrial Gateways category.
Frequently asked questions
Should I choose a GSM or an RF well-tank set?
If the well and tank are within range with no major obstacle between them, the RF set works without a line fee. If the distance is long, the terrain is rough or there is no line of sight, the GSM set is chosen; it needs operator coverage and a SIM line at both points.
Does a LoRa modem need a SIM card?
No. LoRa and RF converters do not use the operator network; they set up a direct radio link between two paired devices. For the same reason they do not provide remote access over the internet.
What does the range of a wireless modem depend on?
On line of sight, terrain and buildings, the antenna type and the antenna height. Values such as 5 km or 10 km in the product data are the upper limit achievable on open ground.
Which model connects existing RS-485 devices wirelessly?
Between two RS-485 points, pairs of G-LORA-485-D10 or of the G-9921, with RS-232, RS-485 and RS-422 options, replace the cable. If the central system must be reached over the operator network, a 4G GSM modem is chosen.