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802.11b WiFi Compliant 2.4 GHz DSSS Wireless ModemIndustrial unlicensed Wireless  Ethernet High Speed  900 MHz OFDM radio modemprotocol to I/O and I/O to I/O Industrial 900 MHz Wireless modem: Master, Remote, Repeater or Repeater-remoteIndustrial 2.4 GHz  protocol to I/O and I/O to I/OWireless I/O extender as Master, Remote, Repeater or Repeater-remoteIndustrial 2.4 G low-cost Wireless protocol to I/O and I/O to I/O discrete/analog I/O extender as Master, Remote, Repeater or Repeater-remoteIndustrial 900 MHz low-cost Wireless discrete/analog I/O extender as Master, Remote, Repeater or Repeater-remote2.4 GHz license-free industrial Wireless FHSS Ethernet radio modem- low power, low cost2.4 GHz license-free industrial Wireless FHSS serial radio modem- low power, low costIndustrial Wireless Ethernet FHSS 900 MHz radio modemIndustrial Wireless Serial FHSS 900 MHz long-range radio modemIndustrial Wireless Ethernet chassis mount 900 MHz radio modem900 MHz Industrial unlicensed Wireless serial modem- low power, low costIndustrial Wireless Serial FHSS 2.4 GHz radio modemIndustrial Wireless Ethernet FHSS 2.4 GHz radio modem

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Wireless Modems

FastLinc FAQ

Smart Spectrum FAQ


Wireless FAQ

Antenna FAQ

See also

See also Technical Services:

Frequency Hopping Spread Spectrum (FHSS)


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Frequently Asked Questions

900 MHz & 2.4 GHz band
wireless modems
Antennas SRM FHSS modems

900 MHz and 2.4 GHz Wireless Modems

license-free serial radio modems

Data-Linc Group's SRM Family of wireless 900 MHz and 2.4 GHz license-free modems— serial, Ethernet, chassis mount and EU versions available

Q: I’ve been reading information about cordless phones that use the 900 MHz and 2.4 GHz band. These articles seem to say that 2.4GHz is better than 900MHz in terms of communication range and noise immunity. Is that true for radio modems as well?
Advances in consumer wireless telephones led to the marketing declaration that 2.4GHz is better than 900MHz. Although questionably true for them, it is not true for SCADA solutions. 900MHz offers longer distance communications than 2.4GHz because 900MHz antennas are larger than equivalent 2.4GHz antennas (termed aperture). Additionally, 900MHz signals pass through objects (trees, foliage, buildings) with less RF loss than 2.4GHz so again, for both indoor and outdoor applications, 900MHz is best. Some years ago the 900MHz band was noisy and the basically unused 2.4GHz, quiet. Today noise in either band is relatively equal.

Q: The application environment is exceptionally noisy electrically (arcing contacts). Will the radio modems be able to cope?
Noise immunity must be designed into the radio modem. Our SRM and PLR products, due to their design are extremely immune to these electrical noise sources.

Q: The radio modems are required to operate in the vicinity of moving cranes. Will they be adversely affected by the varying multiple paths?
All wireless radios are affected by multi-path, some more than others. Reflected (multi-path) RF signals follow longer paths to a receiving antenna than direct signals causing negligible to extreme phase shift and signal energy degradation. Changing the reflected path length or radio frequency changes the impact of multi-paths. Because frequency hopping radios continually change frequency they are much more immune to multipath problems than other radio technologies.

Q: Radio modems are generally known to time-out occasionally for some tens of milliseconds. Are Data-Linc's models immune to this?
The quality of your car’s ride is influenced by the road on which it is driven; the worse road (think RF path) the worse ride (more time-outs). Some cars consistently ride better. Data-Linc radios consistently perform better. They are not immune to time outs (bumps in the radio) but handle them better when they occur

Q: I have a precision real-time SCADA application. Can Data-Linc's radio modems handle this?
In most cases we can operate in precise real-time, as long as the radios throughput specification is not exceeded and the SCADA application can tolerate radio time delay of approximately 10 to 100 milliseconds, depending on RF path quality.

Q: I have an application in Europe. Does Data-Linc Group offer radio modems that can be used in European Union "EU" countries?
Yes, the SRM6100-EU serial radio modem and the SRM6310E-EU Ethernet radio modem are EU compliant. Data-Linc designed both of these SRM Family modems to meet European CE Mark and ETSI RF regulations. The SRM-EU modems combine advanced frequency hopping technology and a highly sensitive RF receiver to maximize transmission range and industrial performance while operating with the constraints of EU regulations.

Q: Without running wires to the pump or tank, what OPTIONS do I have if I need to turn on a pump motor and or read a tank level 5 or 10 miles away?
Data-Linc Group offers two wireless products that can perform these operations— the DDAA1000/SRM and the PLR580D. Please contact Data-Linc to discuss the specifics of your application. (Please see our DDAA1000/SRM and our PLR580D product lines.)

Q: Do exceptional weather conditions significantly impact operation of radio modems in the 2.4GHz band?
It is a scientific fact that RF energy loss in free space (atmosphere) during exceptional weather occurring anywhere on earth is negligible in either the 2.4GHz or 900MHz license-free ISM bands. That said, customers do experience weather related communications interference such as antennas flexing with wind, moisture penetrating a coax cable, antennas encased with ice, moisture on foliage, etc.

Q: What is EIRP and why should this concern me in an RF installation?
EIRP stands for “Effective Isotropically Radiated Power”. This is the amount of power transmitted to the air from the antenna. It is a concern because the FCC limits this to 4 Watts EIRP (+36dBM) for 2.4 GHz multipoint applications. Data-Linc will not supply any antenna package that violates this FCC rule.

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Q: I need to install an antenna on the top of a tower. Does Data-Linc Group provide lightning arrestors?
No but our coax cable assemblies are designed to accept a lightning arrestor, contact Data-Linc Group for a more detailed description of the coax cable assembly you will need for your application. Two companies lightning arrestors can be purchased from are:
Polyphaser Corp.
East Coast Lightening Equip 860-379-9072

They will need to know the "RF" frequency of the radio modems (902-928MHz or 2.4-2.4835GHz), if you use a Data-Linc Group standard coax cable assembly the lightning arrestor will need to have a female "N" connector on the modem side and a male "N" connector on the antenna side.

Q: I will need to use yagis. Should I set them up as vertical or
horizontal polarization?
In a radio network all antennas should use the same polarization. Omni directional dipole antennas are vertically polarized; therefore yagi antennas almost always use vertical polarization.

See also Antenna Installation.

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SRM Family of License-free Spread Spectrum Radio Modems

Q: Will information be secure when transmitted via SRM wireless modems?
The Data-Linc Group SRM series of modems are sophisticated devices that utilize complex technologies including adaptive frequency hopping, proprietary RF (Radio Frequency) packets, data compression and encryption, as well as a wide variety of configuration options. Unlike the 802.11 wireless radios designed for easy and universal access to which security can be applied, the SRM Series is designed for inherently secure and reliable communications. (For a more detailed explanation, read "Data-Linc Group SRM Series Wireless Security: Understanding Wireless Modem Data Transmission" in Articles and Technical Papers.

Q: How can the SRM be used on a DH+ or DH485 network?
A: T
he SRM supports asynchronous data formats in either a 10- or 11-bit word. In order to communicate DH+ or DH485, it is necessary to convert to DF-1 protocol. Allen-Bradley has several ways to do this and should be consulted as to the best method for a given application.

Q: Do I need an RF site survey before installation?
No. For most applications, as long as line-of-sight is maintained, the SRM RF technology will communicate without a problem. Sometimes it may be necessary to perform a visual survey to ensure line-of-sight by determining ideal antenna and Repeater locations. This procedure is certainly much easier— and considerably less expensive— than an RF site survey.

Q: What is the maximum number of Remote radio modems a Master can have on its network?
There is no limit to the number of Remote radio modems on a network. When an SRM is set as a multi-point Master, it will broadcast to any Remote. Only one Remote can talk to a Master at any given time, but the Master is not limited to the number of Remotes that it will talk to. Of course, the PLC protocol used may have a limit, but the SRM will in no way restrict network size.

Q: Why does the SRM6000 require line-of-sight?
It´s not a limitation of the SRM6000 but rather a limitation of the 900Mhz band employed by the SRM6000 Radio Modem. The higher a frequency, the less its ability to reflect off of or pass through obstacles. In some applications, where the range between modems is short, it may be possible to achieve very reliable communications without line-of-sight. Because there are many factors involved that can effect reliable communications under these conditions, it is our recommendation that the technical department at Data-Linc be consulted.

Q: Will the SRM interface with other Data-Linc Group modems?
Yes. All of Data-Linc´s modems have a standard RS232 interface port. Some are protocol transparent, and some require a 10- or 11- bit word. But they can all be linked to each other via their serial ports so that a network of wire modems with radio hops or radio modems with wire modem hops can be achieved.

Q: What advantage do I get by using the SRM6000 whose range is over 20 miles and a maximum port speed of 115.2 Kbps, when all I need to achieve is 2 miles or less at a port speed of, say, 9600 Kbps?
It is true that many applications do not require long range and/or high speed (115.2kbps). The SRM6000 uses frequency hopping spread spectrum technology. Each hop carries a data packet that is checked using CRC 32 bit error checking. If the packet is not correctly received and acknowledged, it is resent on the next hop frequency. This is all being done at the RF modem speed of 144Kpbs. At that speed, even if there is significant interference, the SRM6000 can pass data through accurately without jeopardizing the PLC communications speed of 9600bps or 19.2kbps. Because the SRM6000 can accommodate very long ranges at high speeds, all with a high level of reliability, when the modems are used at shorter ranges with lower speeds, operational tolerance margins provide an enormous safety buffer. This gives the system a level of reliability that is unmatched. Basically, with the SRM6000 you get the best of both worlds.

Q: Why does Data-Linc Group pre-configure the SRM? Is it too complicated to configure in the field?
No. Data-Linc Group does provide pre-configuration on all of its modems, but not because it would be too complicated to do in the field. We pre-configure the units so that the end-user or installer does not have to deal with yet one more task during the installation of an automation system. By providing this service, we increase our level of support to you, our customer - and that´s our number one priority. As to configuring the SRM, all it requires is a terminal program on a PC (or a terminal) set for 19.2Kbaud in a 10- bit word format. You simply push the configuration button and a menu screen is downloaded to the terminal where the changes can be made.

Q: Do I need separate units for Master, Remote and Repeater?
No. Any SRM can be configured as a Master, Remote or Repeater in point-to-point or multi-point systems. Configuration is performed at the factory for specific system applications, but can be as changed as needed in the field via a terminal program as described above.

Q: Do I need two radios and two antennas to make a Repeater?
No. A single SRM is all that is required for a fully functional Repeater.

license-free wireless Ethernet radio modems

Data-Linc Group's license-free wireless Ethernet radio modems

Q: Can Data-Linc Ethernet radio modems withstand harsh environments?
Absolutely. Just like Data-Linc's SRM6000 serial radio modem, the SRM6210E Ethernet radio modem can be used at -40° to +75°F. In addition, it provides the same exceptional data reliability with omni directional antennas (no expensive Yagi required) and has a range of up to 35 miles without Repeaters.

Q: What is the difference between Data-Linc's AE485 and AE422and RS485/422?
Data-Linc uses "AE485/422 2-wire/4-wire" that is compatible with RS485/422 2-wire/4wire. AE, which stands for Auto Enable, is a Data-Linc proprietary technology that is compatible with RS485/422. The default for RS485/422 is receive mode. The AE function allows the device to transmit when data is fed to it without the need for a separate enable signal. Auto Enable is particularly important and beneficial in multi-dropped two-wire 485 and some four-wire 422 solutions. When interfacing with our products, wire count is most important. Please check with non- Data-Linc product manufacturers for their specifications. For further clarification contact Data-Linc at (425) 882-2206 or email

Q: Is there a standard for Ethernet?
The Ethernet network concept was developed by Xerox Corporation in the mid-seventies. Ethernet uses the Carrier Sense Multiple Access/Carrier Detection (CSMA/CD) access method.

There are several types of Ethernet systems. The most popular is the 10BaseT standard for Ethernet networks which uses AWG24 Unshielded Twisted Pair (UTP) cable for connection to the node. The physical topology of the standard is a star, with nodes connected to a wiring hub, or concentrator. Concentrators can then be connected to a backbone cable that may be coax or fiber optic. The node cable has a maximum length of 100 meters; consists of two pairs for receive and transmit and is connected via 10 BaseT plugs.

Q: Where did TCP/IP originate?
TCP/IP (Transmission Control Protocol/Internet Protocol) was developed by the US Government to build a heterogeneous (supporting multiple platforms) network across a wide area of the United States. In the early 1960's, The US Department of Defense (DoD) needed a wide-area, cross-platform communication system. Initially, the TCP/IP suite of protocols was used to interconnect government, military and educational sites together. Later, this protocol suite became a standard for commercial use.

Q: What is "Smart SpectrumTM" technology?
For more information see FAQ Smart Spectrum.

Q: How can I get answers to some other questions I have about data communications and my application?
Email us at or call (425) 882-2206 during business hours Pacific Coast Time for a no obligation consultation.

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