WiFi frequency ranges: 2.4GHz, 5GHz, 900MHz
WiFi Antennas operates at different frequencies to suit different applications.
900MHz：
900 MHz frequency is mostly used for outdoors fixed wireless application , such as SCADA and RFID use the 900MHz .
Advantage :
*Reliable connectivity and signal strength.
*Large range： 900 MHz wireless connection typically has a larger range than a 2.4GHz Wi-Fi connection.
*Greater physical barrier penetration：900 MHz operates on a lower frequency range that allows it easily pass through dense materials such as water, animals, people and tree line between sites etc.
Disadvantages:
*Data Rate availability：The higher the band the greater is the transfer speed.The 900 MHz band is very narrow and this limits the maximum data rates.
*Signal Interference: Compared with 2.4GHz and 5GHz, 900MHz is susceptible to both broadcast as well as tall physical objects on a long range.
* Large Dimension: 900MHz has a much longer wave length that limiting how small the antenna can be
2.4 GHz
Almost all commercial Wireless DMX systems operate in the 2.4GHz band, so it is the most widely used frequency worldwide in some case may be crowded. 2.4GHz is the primary band one uses for WiFi, cordless phone, bluetooth, keyboard, printer and mouse applications. Compared with 900 MHz, 2.4GHz carries larger data packets and increase transfer rates .
Advantages：
*Lowest worldwide harmonized band ,providing best RF performance
*Smaller Dimension
Disadvantages:
*2.4 GHz is more cluttered with signals than 5GHz
* Can not penetrate physical barriers
* Maximum allowed RF power is lower than 900MHz band.
5GHz
The 5 GHz frequency is often used in commercial WiFi applications. Many times it is deployed as a back-up band for systems primarily operating at 2.4GHz.
Advantages：
*Transmit data at faster speeds：The higher the frequency, the higher is the speed ， 5GHz allow data to be transmitted faster than 2.4GHz and 900MHz
*More Non Overlapping Channels
*Less congestion than 2.4GHz
*Very short antenna length
Disadvantages:
*Cannot penetrate solid objects like walls and floors as well as lower frequency signals
*Maximum allowed RF power is lower than other bands, further reducing propagation and range
Design considerations and frequency
The 900 MHz frequency is excellent at passing through trees and walls . 900 MHz is often used in Non-Line-Of-Sight (NLOS) applications.
The 5GHz provides faster data rates at a shorter distance. The 2.4GHz offers coverage for farther distances, but at slower speeds. If faster speeds are most important to you, 5GHz is usually a better choice than 2.4 GHz.If the wireless range is more important to you, 2.4 GHz is usually a better choice than 5 GHz.
But 2.4GHz is a fairly crowded frequency. Most of the current popular standards operate at this level creating a fairly congested environment. In some cases it’s best to use 5 GHz backhaul links to connect 2.4 GHz WiFi networks since 5 GHz is a less crowded frequency.
