Since I've modded scanners with internal GPS units for several RR members, I thought it would be useful to start a thread to cover any technical support issues that may arise, as well as answer questions people may have regarding the process. The following is sampled from the documentation I include with the scanner when I mod it, with a few comments in brackets:
1. [This is specific to the 436. Other scanner models' power taps may behave differently.] The internal GPS module is only powered when the scanner has completely booted and scanning has started. It is NOT powered when the scanner is in Mass Storage mode (such as when updating the scanner with Sentinel) or while the scanner is booting (including loading favorite lists).
2. [This does not apply to Ladybird module installs, which do not require a cutout in the case.] The internal GPS module uses a 25x25mm square ceramic patch antenna installed flush with the rear of the scanner case. Avoid placing metal objects near the GPS antenna, as this will interfere with the received GPS signal, and may prevent the GPS module from getting a satellite fix. Also, while the antenna will withstand reasonable handling, you must protect the antenna from being scratched, crushed, or struck by foreign objects, as this may damage the antenna and/or the GPS module.
3. [The switch location is specific to the 436.] The power switch for the internal GPS is a small white push button on the left side of the scanner just above the battery door. It is flush with the side of the scanner when the GPS is on, and protrudes slightly when the GPS is off. Do not press the switch button with excessive force, or you may damage the switch.
4. When the GPS is active and the baud rate is set correctly in the scanner, you will see a “GPS” indicator in the bottom-right corner of the screen. The on-screen “GPS” indicator does NOT mean the GPS has a location fix, it only means that the GPS is on, and is communicating with the scanner. You must use the GPS status indicator LED to determine whether the GPS has a location fix or not.
5. [The indicator light location is specific to the 436. The color and blink pattern varies, depending on the GPS module installed.] The internal GPS status indicator light is located opposite the scanner’s alert LED under the keypad. It lights up green continuously while the internal GPS is on and acquiring satellite lock. Once the internal GPS module has a satellite lock, the light will flash red briefly once per second.
6. [The Ladybird GPS module does not have a backup battery, and always cold starts.] The internal GPS module has a backup battery to maintain satellite orbit information for a few days when it is turned off. The backup battery is charged when the internal GPS is powered on. When the internal GPS has not been used for a few days, the backup battery will be depleted, and it will take longer to get a location fix—up to 5 minutes if GPS reception conditions are poor. But if the internal GPS power is only off for a minute or so (e.g rebooting the scanner or changing batteries), the internal GPS will reacquire a fix in a few seconds.
7. Running the internal GPS will decrease battery life by about 15%, depending on your scanner backlight settings, volume level, and the amount of scanner traffic you receive. To conserve battery power, you can turn off the internal GPS in situations where it is not needed, and the scanner will continue to use the last location it received from the GPS.
8. You may hear faint electronic noise in the background on some channels while the internal GPS is active. Shielding and other components have been installed with the GPS to minimize this noise, and comparison testing indicates that the internal GPS does not significantly affect receiver sensitivity in digital or analog modes. The noise can be eliminated completely by switching off the internal GPS. When using the scanner as a base, the GPS can be turned off once a location fix is achieved at the base location. The same is true of handheld operation, unless you are riding in a vehicle, or going on an unusually long walk.
9. The internal GPS module operates at 9600bps, which is NOT the default NMEA 4800bps rate. You will need to change the baud rate setting in the scanner profile in Sentinel (it’s in the Location Settings tab) or the scanner setting will revert to 4800bps next time you write to the scanner from Sentinel, and the internal GPS will not be recognized.
10. If you turn the internal GPS off with the GPS power switch, you can still use an external GPS. But be aware that most external GPS units, such as the Uniden BC-GPSK GPS receiver, operate at 4800bps. Therefore, you must change the baud rate in the scanner’s GPS setup from 9600bps to 4800bps when switching to most external GPS receivers, and you must change the setting back to 9600bps before you can use the internal GPS again. In the scanner menu:
Set Your Location
Set Up GPS
Set Serial Port
and then select 4800bps (for most external GPS units) or 9600bps (for the internal GPS). The scanner’s baud rate setting must always match the baud rate setting of whatever GPS is being used, or the scanner will not recognize the GPS.
11. The scanner will receive the correct time from the GPS. However, it is important that the time zone and Daylight Savings Time are set correctly for your location, or the scanner clock will be off by an hour or more. In Sentinel, these settings are located in the Miscellaneous tab of the scanner profile under Clock Options. These settings are also found in the scanner menu:
Settings (you’ll have to scroll down to the bottom of the menu to find it)
Set Clock
Set Time Zone
Set Daylight Saving
Time zones are not named in the scanner menu; they are just listed as the number of hours offset from GMT. Eastern time is -5, Central is -6, Mountain is -7, Pacific is -8, Alaska is -9, and Hawaii is -10.
12. Keep in mind that when you write to the scanner from Sentinel, the scanner settings will be overwritten by the settings in Sentinel, and if you read from the scanner in Sentinel, the settings in Sentinel will be overwritten by the scanner settings.
13. If you have any questions or issues, I can be reached by email at jonwienke@yahoo.com.
1. [This is specific to the 436. Other scanner models' power taps may behave differently.] The internal GPS module is only powered when the scanner has completely booted and scanning has started. It is NOT powered when the scanner is in Mass Storage mode (such as when updating the scanner with Sentinel) or while the scanner is booting (including loading favorite lists).
2. [This does not apply to Ladybird module installs, which do not require a cutout in the case.] The internal GPS module uses a 25x25mm square ceramic patch antenna installed flush with the rear of the scanner case. Avoid placing metal objects near the GPS antenna, as this will interfere with the received GPS signal, and may prevent the GPS module from getting a satellite fix. Also, while the antenna will withstand reasonable handling, you must protect the antenna from being scratched, crushed, or struck by foreign objects, as this may damage the antenna and/or the GPS module.
3. [The switch location is specific to the 436.] The power switch for the internal GPS is a small white push button on the left side of the scanner just above the battery door. It is flush with the side of the scanner when the GPS is on, and protrudes slightly when the GPS is off. Do not press the switch button with excessive force, or you may damage the switch.
4. When the GPS is active and the baud rate is set correctly in the scanner, you will see a “GPS” indicator in the bottom-right corner of the screen. The on-screen “GPS” indicator does NOT mean the GPS has a location fix, it only means that the GPS is on, and is communicating with the scanner. You must use the GPS status indicator LED to determine whether the GPS has a location fix or not.
5. [The indicator light location is specific to the 436. The color and blink pattern varies, depending on the GPS module installed.] The internal GPS status indicator light is located opposite the scanner’s alert LED under the keypad. It lights up green continuously while the internal GPS is on and acquiring satellite lock. Once the internal GPS module has a satellite lock, the light will flash red briefly once per second.
6. [The Ladybird GPS module does not have a backup battery, and always cold starts.] The internal GPS module has a backup battery to maintain satellite orbit information for a few days when it is turned off. The backup battery is charged when the internal GPS is powered on. When the internal GPS has not been used for a few days, the backup battery will be depleted, and it will take longer to get a location fix—up to 5 minutes if GPS reception conditions are poor. But if the internal GPS power is only off for a minute or so (e.g rebooting the scanner or changing batteries), the internal GPS will reacquire a fix in a few seconds.
7. Running the internal GPS will decrease battery life by about 15%, depending on your scanner backlight settings, volume level, and the amount of scanner traffic you receive. To conserve battery power, you can turn off the internal GPS in situations where it is not needed, and the scanner will continue to use the last location it received from the GPS.
8. You may hear faint electronic noise in the background on some channels while the internal GPS is active. Shielding and other components have been installed with the GPS to minimize this noise, and comparison testing indicates that the internal GPS does not significantly affect receiver sensitivity in digital or analog modes. The noise can be eliminated completely by switching off the internal GPS. When using the scanner as a base, the GPS can be turned off once a location fix is achieved at the base location. The same is true of handheld operation, unless you are riding in a vehicle, or going on an unusually long walk.
9. The internal GPS module operates at 9600bps, which is NOT the default NMEA 4800bps rate. You will need to change the baud rate setting in the scanner profile in Sentinel (it’s in the Location Settings tab) or the scanner setting will revert to 4800bps next time you write to the scanner from Sentinel, and the internal GPS will not be recognized.
10. If you turn the internal GPS off with the GPS power switch, you can still use an external GPS. But be aware that most external GPS units, such as the Uniden BC-GPSK GPS receiver, operate at 4800bps. Therefore, you must change the baud rate in the scanner’s GPS setup from 9600bps to 4800bps when switching to most external GPS receivers, and you must change the setting back to 9600bps before you can use the internal GPS again. In the scanner menu:
Set Your Location
Set Up GPS
Set Serial Port
and then select 4800bps (for most external GPS units) or 9600bps (for the internal GPS). The scanner’s baud rate setting must always match the baud rate setting of whatever GPS is being used, or the scanner will not recognize the GPS.
11. The scanner will receive the correct time from the GPS. However, it is important that the time zone and Daylight Savings Time are set correctly for your location, or the scanner clock will be off by an hour or more. In Sentinel, these settings are located in the Miscellaneous tab of the scanner profile under Clock Options. These settings are also found in the scanner menu:
Settings (you’ll have to scroll down to the bottom of the menu to find it)
Set Clock
Set Time Zone
Set Daylight Saving
Time zones are not named in the scanner menu; they are just listed as the number of hours offset from GMT. Eastern time is -5, Central is -6, Mountain is -7, Pacific is -8, Alaska is -9, and Hawaii is -10.
12. Keep in mind that when you write to the scanner from Sentinel, the scanner settings will be overwritten by the settings in Sentinel, and if you read from the scanner in Sentinel, the settings in Sentinel will be overwritten by the scanner settings.
13. If you have any questions or issues, I can be reached by email at jonwienke@yahoo.com.