I’m looking into using the SparkFun LoRaSerial Kit - 915MHz (Enclosed) for GNSS data transmission/reception, but I noticed something peculiar. Most commercial GNSS devices with integrated radio modems operate in the 410–470 MHz range.
Is there a specific reason why the SparkFun kit uses the 915 MHz frequency instead of the more common GNSS radio modem bands? Could it be related to regulatory constraints, performance considerations, or something else?
915 MHz is an ISM band approved in the U.S. for use by unlicensed radio operators, subject to certain restrictions. Band allocation and usage rules differ between countries.
Yes, I understand that there might be a regulatory issue depending on the country. Even so, globally recognized brands like Trimble, Leica, Topcon, South, CHCNav, and others mostly share frequencies in the 410-470 MHz range.
The question is relevant because I am evaluating setting up a reference station with NTRIP and UHF data transmission. However, neither I nor my associates have GNSS devices with radio modems capable of reading the 915 MHz frequency of the SparkFun LoRaSerial Kit
If you want to use Pacific Crest or CalAmp radios, with RS232 and specialize cables, you CAN choose to do that.
The Semtech SX12xx series radios do LoRa modulation in 900/890 and 433 type unlicenced bands, but the packet datagrams, and checksuming methods get to be very different, and this stuff, and Si1000/SiK often used for UAV telemetry is also different, and markedly cheaper.
In the US the 915 MHz is a “junk band” like 2.4 GHz, but with significantly further throw than WiFi at 2.4 or 5.8 GHz. It’s where home/consumer cordless phones, and home WiFi live.
The SparkFun RTK with uBlox, or whatever, just needs a transparent transport, ie the data going in one end comes out the other, no data added or lost, or any added headers and packet size limitations of the underlying transport be it Ethernet, WiFi, Cellular, UAV telemetry radios, or whatever.
In the US, the 410-470 MHz range generally requires an FCC license. The 900 MHz ISM band (again, in the US) allows for unlicensed operation within certain parameters.
The 433 MHz band does turn up in the US sometimes on things like older garage door openers and wireless doorbells. However, they’re very low power/range and can’t carry much data.