Electronic – the purpose of a battery on a GPS receiver

batteriesgps

My GPS receiver has a small MS621FE battery:

GPS receiver PCB

Any ideas what might be the purpose of a battery on a GPS receiver?

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VBAT

This is the battery backup power for the SRAM and RTC when main power is off. Without the external backup battery, ET-662 will always execute a cold star[t] after turning on. To achieve the faster start-up offered by a hot or warm start, a backup battery must be connected. The battery voltage should be between 2.0V and 3.5V

As mentioned in the comments, the main reason this saves time is that it avoids having to wait for the "almanac" of GPS satellite positions to be downloaded.

Related Solutions

Electronic – GPS Units – Weather Balloon

GPS Units are typically limited to controlled airspace (60kfeet, 18km), and 1000 knots. These are commonly known as the COCOM limits. For anything outside of that, you will probably have to go for a higher-end GPS unit and possibly some additional paperwork.

I believe that the uBlox module that is on that board implements the COCOM limits correctly. In the uBlox G5010 datasheet, it gives the operational limits as 972 knots and 50km.

The DoD specification (I believe) says that a GPS unit should not operate above 60kfeet and 1000 or knots, but most of the manufacturers don't actually implement it this way. The commonly cited list of high-altitude capable GPS receivers is here.

Some other companies produce GPS units to spec: most notably Inventek.

Electronic – the talker ID of this GPS receiver

NMEA is used to connect several kinds of marine equipment with a PC, GPS is just one of these. GPS receivers should identify themselves as "GP". (GLONASS has "GL" as talker ID.)

Example GGA sentence:

$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

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Related Solutions

Electronic – GPS Units – Weather Balloon

Electronic – the talker ID of this GPS receiver

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