Sub-GHz Wireless

Governments around the world allow certain wireless frequencies to be used 'license free'. You are probably familiar with the most crowded band, the 2.4GHz  band, which is where most wifi, Bluetooth, ZigBee, and small devices like remote controllers operate. The 2.4GHz band offers a good balance of speed and range, and has a wide 100MHz bandwidth that is available globally, so it is no wonder why this band is so popular for consumer electronics, Bluetooth, and WiFi. But much like having a conversation in a loud room, wireless networks are affected by interference from other wireless devices, and the 2.4GHz band is a very loud room. 

2.4GHz is the go-to band

Whether you are developing a WiFi enabled device, a baby monitor, remote controlled toy car, or a Bluetooth enabled device, the 2.4GHz band is the go-to band because of the high availability of low cost wireless chips and global accessibility of this band without regional restriction. But that ease of use comes at a cost. The 2.4GHz band is quite noisy and is therefore less suited to industrial applications. The issues don't end there - 2.4GHz wireless is absorbed by water, humidity, and water vapor - humid environments and water containing plant canopies can block 2.4GHz signals. Finally microwave ovens use hundreds of watts of 2.4GHz microwaves to cook water-containing food, and stray radio emissions from microwave ovens affect the performance of any wireless device relying on the 2.4GHz band. 

Lower frequency = longer range, lower speeds

Have you ever noticed how low pitched (bass) sounds can easily penetrate through walls, while higher pitched (treble) sounds are muffled through walls? Wireless frequencies are similar. As the wireless frequency increases, the wireless signal tends to become more directional and suited to 'line of sight' operation. Likewise, higher frequency bands can carry more data than lower frequency bands. 

A modern WiFi router has both 5GHz and 2.4GHz bands - this allows for devices that are in a line of sight to communicate at higher speeds at 5GHz, while devices that are separated by walls to communicate at slower speeds at 2.4GHz. But you have probably noticed that your WiFi signal has trouble getting through to the other end of your house, or through multiple walls, floors, and concrete. 

A lower frequency band is available in most regions at 900MHz (or 0.9 GHz) that offers much longer range, more penetration through walls, and no interference from water, weather, humidity, and water vapor. In some point-to-point wireless applications (like pipeline monitoring, electrical grid monitoring equipment, etc), 900MHz devices achieve 20+ mile range with directional antennas. 

One tradeoff to using the Sub-GHz band is that these frequencies are not capable of high speeds, and sub-GHz networks are slower for applications like imaging and video. This speed limitation is the primary reason the Sub-GHz band is not crowded today and will likely remain so. For high reliability automation purposes - such as sending schedules, sending real time control data, and sensor data - the Sub-GHz band provides more than enough speed for essentially instantaneous response times.  

GrowFlux's unique implementation of 900MHz wireless

GrowFlux uses industrial wireless microprocessors and the GrowFlux Mesh firmware stack to enable reliable wireless communications in our devices. We design-in high efficiency omni-directional internal antennas and avoid the use of internal RF connectors to prevent quality control issues that can affect wireless performance. We also tune our wireless circuitry with simulations, precision vector network analyzers, anechoic RF chambers, and real world testing to push as much performance as we can get from our devices.

Finally, we use high performing RF components (such as high Q inductors, discrete baluns rather than integrated baluns, specialized circuit board materials) to optimize the efficiency of our RF circuits as much as possible. All together, this results in real world line-of-sight range of up to 2.5 kilometers between our Access Point and Universal Dimmer, and over 1 kilometer range for many of our smaller devices. 

Taking Sub-GHz a step further

In addition to using Sub-GHz wireless frequencies, GrowFlux Mesh also utilizes channel hopping to dynamically adapt networks to noisy RF environments, ensuring reliable communications regardless of the wireless environment. 

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