How to Make a Frequency Selection for Microwave Radio Communication
Select a microwave radio system to expand your computer network to another location up to 30 miles away. The main criteria include bandwidth and reliability. Select bandwidth for speed and density of your traffic, then select a suitable frequency. First select between unlicensed and licensed, and then a frequency band. For unlicensed frequencies, you may select from the available group. For licensed frequencies, after you choose a band, the FCC will assign a specific frequency with your license. You should not order equipment or begin construction of your licensed system until the FCC assigns the frequency and grants the license.
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Instructions
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Select an unlicensed frequency. Available frequencies are typically 2.4GHz, 5.3GHz, 5.4GHz, and 5.8GHz. All frequencies are exact and you may not alter them. All may reach 30 miles, but the 2.4 GHz is less affected by rain or snow. Since they are unlicensed, there are no records of which frequencies are already in use in your area. The more densely populated the area, the more likely the system will suffer interference. You are at your own risk. If you don't want to take the risk, apply for a licensed frequency.
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Select a general licensed frequency band. Typical available bands are 2GHz, 6GHz, 11GHz, 18GHz and 23GHz. 2GHz goes the farthest and is the least affected by weather, but may not carry the bandwidth needed for high-speed systems. 6GHz may reach up to 30 miles, but with some signal loss from weather. 11, 18 and 23GHz systems reach a maximum of 11 miles, depending on weather and other atmospheric conditions in the area.
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Purchase a frequency coordination study for your area. The FCC maintains a partial list of microwave coordinators at fcc.gov. Prices vary between companies and some give discounts for multiple studies. The FCC does not recommend or guarantee any company, but does require you to purchase a study before applying for a license.
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Apply for an FCC license. You may submit an application online at fcc.gov. You must include all relevant information including the band in which you're applying, your type of service, the geographical coordinates of the sites, the sizes, types and heights of the antennas and the proposed radiated power at each antenna. The FCC may grant your license, ask for modifications to your proposal or inform you that no frequencies are available. When they grant the license, they assign a specific frequency.
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Order your microwave radio from the manufacturer at the frequency assigned by the FCC. If you wish to change the frequency, you must apply to the FCC for a change.
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Tips & Warnings
Contact several microwave radio manufacturers for advice. Many will assist you in making your decision between unlicensed and licensed. Some will do a free path analysis in their cost proposal and provide you with information you need to apply for the license. Some will include all licensing services in a "turnkey" price.
If you have interference on a licensed system, the FCC will help you resolve the problem. With an unlicensed system, you're on your own.
Microwave radio antennas must have "line of sight," meaning a clear path with no obstructions.
An unlicensed radio always runs the risk of interference. Someone could install a new system at any time that interferes with yours. Interference is less probable in rural areas.
With a licensed radio, never transmit outside of your assigned frequency or above your assigned power level. You could be subject to fines or other penalties.
All microwave systems experience outage times, but the overall design of your system determines reliability. Consider antenna gain, transmitter power, distance between antennas and the atmospheric conditions in your area. A system designed for 99.999 percent reliability means it would be out of service only about five minutes a year; 99 percent, 3.65 days per year. Consult a microwave path transmission engineer for assistance in designing your system.
References
Resources
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