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Garmin 18x LVC GPS Navigator Unit
|Price:||$64.51 & FREE Shipping. Details|
- High Sensitivity LVC Sensor with Bare Wire Connection
- WAAS Enabled High Sensitivity GPS Receiver
- Comes w/A Connector End that Can Attach to a CMOS for OEM Applications
- Non Volatile Memory for Storage of Configuration Information
- Raw Measurement Output Data for Sophisticated Customer Applications
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Top Customer Reviews
But the 18x models with connectors DO NOT output the precision measurement pulse, so they are useless as reference clocks. You may wonder why anyone would need a clock accurate to within 1.0 microsecond. The clocks inside computers are notoriously inaccurate, sometimes up to an hour off per day. So, the Internet is peppered with reference clocks. People interested in time keeping will place a reference clock server online, and thousands of Desktop PCs also connected to the Internet can poll these servers to accurately set their clocks. The reference clocks need to be accurate, because of dispersion in distribution (i.e it takes a small bit of time for the client PCs to receive the time from the time server. Having microsecond accurate time servers insures no client will ever drift past 1/2 second from UTC.
It's all automated. The user doesn't do anything. It just happens. So that is what this particular unit is for, from a retail perspective. There is a web page, [...] , explaining in very simple terms how to make a time server. Soldering skills are required for individuals to make use this unit. The 18x USB, not the 18x LVC, is handy for navigation via a laptop.
As the LVC model is a "barewire" model meant for OEM integration, it requires a little bit of soldering to get setup the way one wants. I opted to connect the GPS to a small circuit board that supplies power to the GPS, has a fuse, and has indicator LEDs to show the state of the GPS: one LED shows that power is applied, with another LED shows when the PPS signal is transmitted. The circuit board has a DB-9 serial connection to the computer. Other people I know have connected the PPS and data wires directly to a DB-9 serial port and the power/ground wires to a male USB-A plug without any LEDs. Either way works fine -- the GPS draws about 60mA by itself (mine draws 75mA with the LEDs) and so can be powered easily off of a USB port (which can supply 100mA without the device needing to ask for more power).
It's difficult to rate the GPS unit itself as it's so simple and there's not a whole lot of features: supply it with power, let it see the sky, and it starts outputting data. It managed to find an initial lock and output PPS signals within about 3 minutes of when I turned it on for the first time. Since then, it's able to reestablish a lock within about 5 seconds after being powered down and turned back on again. For testing purposes, I have it inside my apartment on top of a box placed next to my northeast-facing window and it is able to see between 5 and 9 satellites depending on the time of day.Read more ›
USB based GPS units are useless for accurately setting the time.
The 18x LVC GPS unit requires 5 volts of power (red wire), and for this I use a specific serial card, the StarTech.com 1 Port PCI RS232 Powered Serial Adapter Card (PCI1S650PW). The card can be configured to supply either 5 or 12 volts (or none) on pin 9 of the RS-232 DB-9 connector, and can draw power either from the PCI bus itself or from the PC power supply directly via the onboard Molex floppy power connector. (I used the latter option). Once the jumpers had been set and the card installed no drivers were required for Debian, Setserial recognizing the card as having a 16550A UART with a baud base of 921600.
The GPS unit itself is mounted externally on the chimney, as the GPS satellite signals are fairly weak, so installing outside is the best option as the GPS itself is weatherproof. For me, this location gives the GPS a clear view of the sky, but the 5 meter (16 feet) cable would not be long enough to reach the computer inside the house, so I replaced almost all of the original serial cable (which is molded onto the 18x LVC). The wires (especially the three signal wires, which includes the PPS) are also *VERY* thin. So, I cut the original cable close to the GPS unit itself and extended it with my own cable which runs all the way back to the computer and is terminated with a serial DB-9 connector. If you do this, remember to use a shielded cable.Read more ›
Most Recent Customer Reviews
Locks on strong from a window, but is weatherproof for mounting outdoors. A good choice for a DIY GPS-synched Network Time Protocol (NTP) clock on a budget. Read morePublished 28 days ago by Robert Levandowski Jr.
Great price and a very good unit. Delivery time was quick! Good job Amazon!Published 6 months ago by Chester Curtis Gill
This unit works perfectly. I'm using it purely for its 1 PPS output for time synchronization and for the price it can't be beat for that purpose.Published 14 months ago by Matt Hornsby
Purchased this unit to use as a GPS disciplined NTP network time server. Added a DB9 serial connector on end of cable, plugged into a Debian-based NTP server and I am in business... Read morePublished 17 months ago by jabit