A question we are often asked by our new customers purchasing their first Trimble GPS system for use in land surveying, construction and mining applications:
Is an FCC license required for transmitting RTK corrections over UHF (450 MHz)?
Radio type: UHF (ultra-high frequency) Frequency range: 403-473 MHz
YES – REQUIRED – including all power levels.
It’s a misconception that transmitting at lower power (under 2 watts) does not require a FCC license. Per the FCC, any transmission - at any power level in the UHF spectrum requires a license within the United States. That includes the low power internal radios integrated into receivers like the R8, R10, R12...etc.
Is an FCC license required for GPS receivers that utilize a 900 MHz radio?
Radio type: 900 MHz (902-928 MHZ)
No. A license is not required within the US, Canada, Australia and New Zealand.
Note: In ANZ and AUS Trimble 900 MHz radios are restricted to a portion of the 900 MHz spectrum by regulations in those countries. For this reason, Trimble 900 MHz radios are limited to a smaller frequency range and number of channels, but still offer the same performance.
Is 900 MHz license free everywhere?
No. 900 MHz for GPS / RTK use is restricted from use in some countries, including: South Africa, Thailand, South Korea, and the UAE.
Why choose 900 MHz vs 450 MHz?
900 MHz radios are popular with most construction applications as they do not require a license and because the provide excellent coverage up to 3 miles away from the base station receiver. It's the same technology used in most cordless home phones (remember those?).
Land surveyors tend to choose UHF radios over 900 MHz because UHF radios are capable of transmitting at high power (35 watts), which can travel longer distances - as far as 20 miles away from the base station.
Why do you need a radio for GPS systems (RTK)?
If you need GPS accuracy, you need RTK technology. Real-Time Kinematic (RTK) is the technology used by GPS / GNSS receivers that enable real-time, centimeter-level accuracy. RTK correction data is sent to your GPS rover over the air by either radio, cellular, internet or satellite.
Without RTK corrections, your GPS / GNSS receiver’s accuracy is 3-feet / 1-meter at best. That’s right, even the most advanced “survey-grade” GNSS receivers like the Trimble R12i, SPS986 and R780 can only provide 3-feet of accuracy when RTK corrections are not available.
How RTK works (the basics):
RTK requires two GPS / GNSS receivers that are simultaneously tracking satellites – a base station receiver and a rover receiver. The base station receiver is fixed at one location, typically on a tripod. The base station takes continuous measurements from satellites as they fly overhead. As mentioned before, any GPS receiver by itself is only accurate to roughly 3 to 10 feet. The genius of RTK technology is by tracking the base station’s actual fixed position (on the tripod), while simultaneously measuring the distance and direction of it's position error, it can instantly calculate and “correct” for its true position. It then broadcasts its corrected position to your GPS rover receiver(s). The GPS rover then applies the corrections to calculate its own position, providing centimeter-level, real-time accuracy in 3 dimensions.
One base station can transmit RTK corrections to multiple rovers - as long as they are within radio range and less than 25 miles (RTK accuracy limitations).
Where to apply for an FCC license for RTK?
The FCC (Federal Communication Commission) is a department of the US government tasked with managing all radio communications within the United States.
The FCC uses Frequency Coordinators to assist customers with applying for an obtaining their FCC license. There are several Frequency Coordinators listed on the FCC’s website (link provided below).
Recommended Frequency Coordinator:
FOREST INDUSTRIES TELECOMMUNICATIONS (FIT)
FIT helped us and many of our customers obtain our FCC license quickly.
Link to: FCC application on FIT's website >>
How long will it take to get my FCC license for RTK?
It took roughly 45 days to process and receive our FCC license.
What is the cost to obtain your FCC license for GPS / RTK:
At the time of writing this article, we paid $475.00 to obtain our FCC license which included two channels / frequencies.
I have my FCC license - Now what?
Once you have your FCC license we can program your assigned frequencies into your radios and GPS receivers. Depending on your application you will typically receive 2 frequencies specific to you and your location. Additional frequencies can be requested at the time of your application.
Programming transmit frequencies requires special software that only authorized Trimble resellers have access to. Your frequencies are assigned to the serial number of your radio or GPS receiver and can be emailed to you in what's called a ".set" file. You can then install the .set file into your GPS receiver or radio.
With your own assigned frequencies, you shouldn't have any trouble getting mixed signals from other surveyors in your area. However, it's good practice to use the "listen" feature built into your radio before transmitting. If someone is transmitting on your assigned frequency, you should select another frequency to transmit on.
Helpful Links:
- Trimble – What is RTK
- Trimble Support Bulletin: FCC Narrowbanding Requirement for UHF radio (2013)
- FCC license information for UHF radios (FCC website) >>
- Trimble - What is RTX