Choosing a good wireless channel

The 2.4GHz frequency band is used by many wireless devices these days, from Bluetooth headsets, to WiFi base stations, to our Opal movement monitors. Because of this, it is increasingly possible to experience wireless interference between these devices. This can result in poor behavior when using our Opals in the wireless streaming mode.

There is actually a range of frequencies around 2.4GHz, and most devices only use up a relatively small slice of this. You can therefore often resolve wireless interference issues by finding a slice, or channel, that is not currently in use or at least not heavily in use. Radio frequency scanners are not very common and can be expensive, but there is an easy way to find what parts of the spectrum are being used by the biggest offenders - WiFi base stations. Here are some steps you can take to help resolve :

• Use a wifi scanning tool. We recommend "WiFi Analyzer" for the Android platform, because it is free and works well. There is not a similar app for iPhones/iPads due to App store license restrictions, but there are options for both Windows (Acrylic WiFi) and OSX (WiFi Scanner) PCs. They all basically work the same, by providing information about which channels are being used and the strength of the signal at which channel.
• Note that WiFi channels do not correspond to Opal channels. Opal channels are relative to the absolute frequency, where WiFi channels are not so. Our channel 2, for example, corresponds to 2.42GHz (WiFi channel 2/3), and our channel 6 corresponds to 2.46GHz (WiFi channel 10/11). See the plot below for the relationship between WiFi channel and frequency.
• Find a location in the spectrum where there is not an existing wifi signal or where it is least crowded. Note the corresponding Opal channel. This will be the channel you configure the Opals to communicate on.
• Note that each 3 Opals require their own channel, and additional Opals will be configured to record on a channel 7MHz higher. For example, if you configure a set of 6 Opals on channel 30, 3 of the Opals will use channel 30 and the other 3 will use channel 37. If you configured 8 Opals instead, the last 2 Opals will be configured on channel 44.