Hello,
The problem I’m seeing, as listed in the title, is twofold. First, I’m seeing relatively unstable Signal to Noise ratio. It will often range from an SnR of 17 to an SnR of 30 for both of my NEO-M9N GPS units, usually sitting at around 25. These values seem lower than what I would expect from the performance of this hardware. The second issue is that during operation my GPS units often take a long time to lock when first turned on, especially if moved to a new location. This wait time can be as short as 15 seconds and as long as 30 minutes.
I’m currently working on integrating two NEO-M9N GPS units (Found here:https://www.sparkfun.com/products/15712) on an off-road application. The Boards themselves are mounted on top of each other inside of the vehicle as displayed in the attached file “GPS_Mounting.png”
These exterior of the vehicle is plated with steel, fully encasing the GPS modules. There is wire routing to the antennas on the exterior.
These units each utilize a 8" UFL to SMA cable converter as well as a 3m Magnetically mounted SMA antenna (Found here: https://www.sparkfun.com/products/14986).
My configuration settings are as follows:
SBAS: * num search channels: 1
- All the rest stay the same
RATE: * measurement period: 500ms
PRT: * targets: UART 1 & 2
-
Protocol Out: 1 - NEMA
-
115200 Baud Rate
NMEA: * Permit COG if frozen ENABLED
NAV5: * Portable
MSG: * NEMA GxGGA
UART1 ON
UART2 ON
USB ON
- NEMA GxGLL
Blank
- NEMA GxGSA
UART1 ON
UART2 ON
USB ON
- NEMA GxGSV
UART1 ON
UART2 ON
USB ON
- NEMA GxRMC
UART1 ON
UART2 ON
USB ON
- All the rest blank
Are the SnR values I’m seeing typical of units like this? Are the long lock times also to be expected, or is there something suboptimal about my configurations and my setup?
Thanks for any feedback that can be provided.
-Casey