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1200 Baud Bell 202 Radio-Modem Replacement

radio modem replacement

1200 Baud Bell 202 Radio-Modem Replacement. There are few instances where technology deployed in the 1980’s is still around, compatible and even usable. 

In the 1980’s, 1200 Baud Bell 202 AFSK based modem systems were commonly deployed for Radio and Wireline Data Communication Systems in SCADA Systems. These systems were robust and long lasting. Many of the Bell 202 based Radio systems utilized mobile radios connected to external Bell 202 modems. Many of these systems are still in use, but they are aging and about to fail.  It is highly recommended to update them before they fail.

The following scenarios will inevitably play out: 1)The two-way radios may fail, and/or 2) the external modem may fail.

Due to product obsolescence there are no plug-in replacements available for the two-way radio or the external modem. So when a site fails, components will need to be repaired in the field or on the bench, however these repairs require expertise in analog electronics. Starting in the 90’s there has been knowledge loss due to retirement of old-time technicians specializing in analog electronics. It is now difficult to find a technicians available with the know-how to repair these legacy systems.

At SCADALink, we have had extensive experience in repair and troubleshooting of aging SCADA systems  – SCADA Communications Troubleshooting.

Emergency Field Repair

We have assisted in emergency field repairs of failing Bell 202 based systems where the 1) Radio Failed, 2) the Bell 202 Modem Failed, or 3) Modulation was out of adjustment.

Repairs were hampered by various factors including:

  • difficulty in compatibility of RF or Modulation levels with replacement equipment
  • lack of documentation of legacy equipment for maintenance
  • lack of availability of replacement equipment
  • connector problems

Network Upgrade Options

There are two ways to deal with this obsolescence problem:

1) Install New Modem Technology with 1200 Baud Bell 202 Compatibility

Systems can be replaced with integrated RF modems that have Bell 202 modulation.
… Modems with Bell 202 Compatibility

One challenge with the type of replacement is that in some installations, the higher RF output of the 25 Watt two-way radios was required to provide adequate fade margin in some data links.

2) Technology Replacement

Alternatively, the obsolete RF Systems can be replaced by new RF technology, either in the same RF band or different bands such as licensed free 900 Mhz, or cellular modem systems. 
..see Replacement Technology