Some notes on fault-finding GNSS reception problems
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GNSS is an acronym for Global Navigation Satellite System and covers all the systems , namely GPS; GLONASS; Galileo; QZSS and Beidu.
The displayed position of a MOTOTRBO radio will probably not be as good as what is shown on a mobile phone or in car navigation system. The navigation system uses a feature called snap-to-road which assumes the car is on the closest roadway. Google Maps uses your, and your neighbors' Wi-Fi SSIDs, to augment any location data. If you are in a shopping mall or airport, applications like Google Maps will use iBeacons to get positioning data.
When turning a MOTOTRBO radio on, it will require 1-2 minutes to get a fix. This is known as a cold start. The duration needed to get the fix is known as the Time To First Fix (TTFF).
If a radio user goes into a tunnel or building and comes out again, the GNSS receiver will need a few seconds to get a fix again. This is known as a hot (or warm) start.
In a cold start state, the GNSS receiver only has a valid almanac stored; it does not have any valid satellite ephemeris (there's a new word for you!) data nor valid real-time clock synchronization. Almanac data is stored in non-volatile memory and is valid for around one year. Under normal operating conditions, the radio's GNSS receiver will regularly update the almanac data. The almanac data provides mapping of the satellites’ position in the sky in relation to a real-time clock.
A fix means the receiver has a signal of greater than -130dBmV from at least three satellites.
To improve accuracy, some MOTOTRBO models support the selection of a combination of two GNSS systems. This won't improve the time to first fix but will improve the accuracy under less than ideal circumstances.
Accuracy is represented in the radio as HDOP (more accurately Geometric Dilution Of Precision). This is a dimensionless number that represents the difference between the actual position and GNSS measured position. A GDOP of 1 means that the fix is as accurate as possible, though anything below 5 would give reasonable results.
To get the best results from a MOTOTRBO radio, I recommend only turning the radio on when in an area with full view of the sky. If you are using a portable radio, try to hold the radio away from your body.
On radios with a display, an icon (shown above) gives the user a means to know whether a fix is possible. If the above icon is not shown, GNSS is turned off.When turning a MOTOTRBO radio on, it will require 1-2 minutes to get a fix. This is known as a cold start. The duration needed to get the fix is known as the Time To First Fix (TTFF).
If a radio user goes into a tunnel or building and comes out again, the GNSS receiver will need a few seconds to get a fix again. This is known as a hot (or warm) start.
In a cold start state, the GNSS receiver only has a valid almanac stored; it does not have any valid satellite ephemeris (there's a new word for you!) data nor valid real-time clock synchronization. Almanac data is stored in non-volatile memory and is valid for around one year. Under normal operating conditions, the radio's GNSS receiver will regularly update the almanac data. The almanac data provides mapping of the satellites’ position in the sky in relation to a real-time clock.
A fix means the receiver has a signal of greater than -130dBmV from at least three satellites.
To improve accuracy, some MOTOTRBO models support the selection of a combination of two GNSS systems. This won't improve the time to first fix but will improve the accuracy under less than ideal circumstances.
Accuracy is represented in the radio as HDOP (more accurately Geometric Dilution Of Precision). This is a dimensionless number that represents the difference between the actual position and GNSS measured position. A GDOP of 1 means that the fix is as accurate as possible, though anything below 5 would give reasonable results.
To get the best results from a MOTOTRBO radio, I recommend only turning the radio on when in an area with full view of the sky. If you are using a portable radio, try to hold the radio away from your body.
The GNSS antenna is built into a portable radio. On the DP4000e series and R7, it is inside the radio's front cover. The DM4000e series requires an external antenna.
The external antenna used with a mobile radio must be in a position that allows it to get a full view of the sky. Mounting the GNSS antenna on the dash or backboard (i.e. inside the vehicle) will result in poor performance as all modern car glass has a metallic (or some other) coating that attenuates the 1,5GHz signal using by all the GNSS systems.
The external antenna is an active device and requires a 5VDC supply from the radio. If there is cable fault, the full supply voltage may not reach the antenna and the fix will either be poor or there will be no signal at all (no/poor GNSS reception icon displayed).
Since the antenna is an active device (LNA), it could become faulty and stop feeding the radio a signal, even though the cable is good and 5V is present on the SMA connector. An active antenna is needed for mobile radios to overcome the ca. 8dB loss presented by the coaxial cable (PMAN4000A uses 5m of RG174).
The GNSS receiver in the mobile and portable can filter out of band signals quite well but it cannot cope with in-band or intentional interference (jamming).
Since the antenna is an active device (LNA), it could become faulty and stop feeding the radio a signal, even though the cable is good and 5V is present on the SMA connector. An active antenna is needed for mobile radios to overcome the ca. 8dB loss presented by the coaxial cable (PMAN4000A uses 5m of RG174).
The GNSS receiver in the mobile and portable can filter out of band signals quite well but it cannot cope with in-band or intentional interference (jamming).
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