There are several ways you can consider cutting your system over from an old wireless system to a new one. Significant thought and effort should go into the process well in advance. Here are a few options for you to consider, but if you have any concerns or questions please feel free to contact the SCADA and Telemetry team, or leave a response here.
1) Two serial port option
Install the new Master site radio and an antenna for it. Keep the new antenna some distance from the old one, but preferably in an as-good or better location. They don’t have to be too far apart if vertical, eg approx. 3 metres (10 ft), but if horizontal perhaps 30 metres (100 ft). Only one will transmit at a time. If the new antenna is not in as good a location as the old one, after all radios have been switched to the new system, move the new antenna to the better location. The SCADA Host computer will need a second serial or LAN port, and will be re-configured so that as new sites are added they are polled on the second port, which is connected to the new Trio master radio. Add sites beyond any necessary repeater only after that repeater radio has been added and tested. Until all old radios are removed, they will continue to be polled via the old master radio on the first comm port.
2) Two-channel option
First thing to do in this option is to apply for a new SCADA license to the FCC. An agency such as National License or Enterprise Wireless Alliance can help with the application for a fee. Tell them that the old license will be relinquished after the cut-over. Request a new frequency at least 5 MHz away from the existing channel assignments. This can take a few weeks. Install a new Master site antenna near the old one. Preferably directly above it, with as much vertical separation as possible. If you can’t do that, get as much horizontal separation as possible. Physical separation (vertical is better) combined with a wide frequency separation, ensures that both systems can operate at the same time without interfering with each other. If using serial communication, add a serial port splitter (eg from Black Box) so both master radios get all messages. Both will send all messages at the same time.
3) The “Hail Mary” option
Configure all of the radios in advance, and test them as fully as you can on the bench. A Trio 4, 6 or 12-port attenuator can be used to keep signals contained while testing. After you’re as sure as you can be that the configurations are right, physically install the radios at all sites, but leaving the old radios operational. Make sure that you’ve got the correct power, antenna and serial cables ready to go. Then (on a Tuesday morning!) you swap out the Master radio to a Trio Q. After that you go around to each of the remote sites in turn, and if all is prepared correctly all you should have to do is swap the radios and cables. If you have some sites that are more critical than others, do the most-critical sites first. If carefully done, this option can be the least work and quickest, but it’s critical to get the radios configured, tested and installed properly in advance. And be ready to swap back to the old system if something isn't working right.
4) Antenna-Sharing with a Duplexer
This is similar to option 2), where two wireless channels are needed. It requires, however, that your original license be a Simplex license. (one frequency for both Transmit and Receive) If it’s a Duplex license (two separate frequencies) this won’t work. Rather than install a second antenna, which may possibly be very difficult to install in a good location, you install a duplexer so both the new and old Master radios can share the existing antenna. As long as the two frequencies are (approximately) 5 MHz apart, a duplexer can keep the signal from one radio out of the other radio, while both share the antenna. After the old radio is de-commissioned, the duplexer can be removed and re-sold. An example of a duplexer is Trio's model TBUMDUPLX4XXCOA.
Communication Port Upgrading
One further item to note is that if the original system operates with serial ports rather than Ethernet, Trio's Q and J data radios are able to transport both serial and Ethernet. Serial messages may be encapsulated in a UDP or TCP transport layer. After old end devices such as RTU's or PLC's are replaced with new Ethernet-capable models, the new devices can simply be connected to the radio's LAN port with no further configuration.
Joel Weder Telemetry Solutions Specialist Schneider Electric