11.0 GHz Band
Understanding the 11.0 GHz Band
If an Internet Service Provider (ISP) or cellular company needs to bridge a 15-mile gap across a valley, they face a severe physics problem.
- They cannot use 5 GHz Wi-Fi. The band is completely ruined by unlicensed interference from home routers, and the channel sizes are too small to push true Gigabits.
- They cannot use 80 GHz E-Band. The 80 GHz wave is so fragile it will be entirely absorbed by rain after just 2 miles.
The global solution is the 11.0 GHz Band.
The Engineering Sweet Spot
Operating at a wavelength of roughly 2.7 centimeters, the 11 GHz band provides the exact physical characteristics required for long-haul, high-capacity infrastructure.
| The Requirement | The 11 GHz Reality |
|---|---|
| Rain Fade Resilience | While 11 GHz is affected by torrential downpours, its 2.7cm wave is physically large enough to "step around" standard raindrops. With proper antenna sizing, an 11 GHz link can guarantee 99.999% uptime (only 5 minutes of downtime per year) over a 15-mile shot. |
| Channel Capacity | The band is allocated in massive chunks, commonly utilizing wide 80 MHz or 112 MHz channels. By injecting 4096-QAM into an 80 MHz channel, a single 11 GHz radio can push over 1 Gigabit per second full-duplex. |
| Interference Protection | It is strictly licensed. An operator must apply to the FCC (or local government) to rent the specific frequency path. Once licensed, the government legally guarantees that no one else in that city is allowed to point an 11 GHz radio in the same direction, ensuring a completely flawless, noise-free link. |
The Hardware: 2-Foot and 3-Foot Dishes
To achieve the required gain (often 35 to 40 dBi) to push an 11 GHz signal 15 miles, engineers must mount massive parabolic dish antennas to the tower. The standard sizes are 2-foot (0.6 meters) and 3-foot (1.0 meter) diameters. These dishes require incredibly rigid, heavy-duty mounting hardware, because if the wind blows the tower and knocks the dish off-axis by even 1.5 degrees, the pencil-thin 11 GHz beam will completely miss the receiving tower on the other side of the valley.
Key Equations
The 11.0 GHz Band (typically encompassing 10.7 to 11.7 GHz) is an internationally harmonized, heavily licensed slice of the microwave spectrum serving as the foundational...
Key specifications:
11.0 GHz | 11.7 GHz | 11 GHz | 20 m | 5 GHz
Power: P(dBm) = 10log(PmW), 0dBm = 1mW
Comparison
| Band | Range | Wavelength | Application | Standard |
|---|---|---|---|---|
| 11.0 GHz Band | 11 GHz region | 27.3 mm | Primary use | ITU allocation |
| Adjacent lower | 9.9 GHz | 30.3 mm | Related band | Shared spectrum |
| Adjacent upper | 12.1 GHz | 24.8 mm | Related band | Guard band |
| Harmonic 2f | 22.0 GHz | 13.6 mm | Spurious | Filter required |
| Sub-harmonic | 5.5 GHz | 54.5 mm | LO option | Mixer design |
Frequently Asked Questions
How much does an 11 GHz license cost?
In the United States, obtaining an FCC Part 101 license for an 11 GHz microwave path typically involves a one-time frequency coordination fee (around $1,000 to $2,000) and a small government licensing fee. The license is usually valid for 10 years. It is incredibly cheap insurance to guarantee a gigabit backbone link never suffers interference.
Can you use 11 GHz indoors?
No. The FCC explicitly restricts 11 GHz hardware to fixed, outdoor point-to-point operations. The massive power output and highly directional nature of the dishes make it entirely unsuitable and illegal for omni-directional indoor Wi-Fi networks.
What happens if a bird flies in front of the dish?
A single bird will not drop the link. The 11 GHz beam is slightly wider than the bird by the time it leaves the radome of the dish. While the bird's watery body will scatter a tiny fraction of the microwave energy (causing a brief, microscopic drop in signal strength), the receiver's error correction (FEC) will easily catch the missing bits. However, a flock of large birds roosting directly on the feed horn will destroy the VSWR and crash the link.