The SparkFun GNSS L1/L5 Breakout board (SKU: GPS-24114) is a compact, low-cost (USD$41.50 Nov 2025) board built around the u-blox NEO-F10N dual-band GNSS module. This module has a 1 PPS timing signal suitable for use with the ultramsk VLF receiver software. SparkFun have done a great job with their breakout board for this module. You need to wire up the PPS signal to a suitable connector for input to one channel of your computer’s sound card. The device is powered via a USB-C connection.
Features & Specs
- 1x USB Type C Connector
- ESD Protection Diodes for USB Data Lines
- CH340C USB-to-Serial Converter
- Integrated SMA Connector
- Concurrent Reception of GPS, Galileo, and Beidou
- Receives L1/L5 Bands
- PPS Time Pulse Accuracy: 30ns
To use this module in an UltraMSK VLF receiver you need to bring out the PPS and GND signal to a suitable connector. You will also want an enclosure for the board. I used a small plastic box with a clear lid to allow the onboard power and PPS LED indicators to remain visible. I’ve wired the PPS signal, along with GND line, to a BNC connector. A short SMA extension cable was used for the antenna connection. For the USB-C connection, a suitable sized opening was made in the enclosure box. See photo below.
The 1 PPS pin is 3.3 V logic. You may need to attenuate the 1PPS signal to match the input voltage range of your soundcard. If so you will need to hold the “SAFE” pin high with a 6.2 kOhm resistor. See the ublox NEO-F10N documentation for more details on the safe boot mode of the module.
You’ll also need a suitable GNSS L1/L5 antenna. SparkFun has the u-blox Multi-band Active GNSS Antenna – L1, L5 (ANN-MB5)