Inexpensive OEM GPS Receivers

With PPS

Garmin GPS-18LVC

• Refclock Driver: Type 20
• PPS: +- 1us
• Cost: ~$70 - $80 (2007-11-10)
• Specifications: http://www8.garmin.com/products/gps18oem/spec.html
• Performance / Statistics
• Examples / HOWTOs:
  • Simple guide to using the GPS-18LVC on a spare PC with FreeBSD - DavidTaylor
  • Using a Garmin GPS 18 LVC as NTP stratum-0 on Linux 2.6

Without PPS

Globalsat BR-355, BU-353 and other modules using the SiRF chip sets.

• Refclock Driver: Type 20
• Cost: ~$50 - $70 (2007-11-11)
• Specifications: http://www.globalsat.com.tw/eng/product_detail_00000043.htm

These don't work very well. They have two problems.

1. First is that they have a lot of jitter/wander. (The jitter is too low frequency to easily filter out.)
2. Second is that they have a strange off-by-a-second bug if there is a leap second pending. This graph shows both quirks.