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120 20110-003  PRELIMINARY

Gemini/PD   Technical Manual

7

3.4.5  GPS Diagnostics Procedure

OVERVIEW
The detection of the POSition message shows a GPS CONNECTED LED. After about three
minutes, detection of the one Pulse Per Second (PPS) should flash the POSITION ACQUIRED
indicator, this means that the GPS has a position solution.

If the GPS has a good view of the sky and still has not generated any position solution within
three minutes (it may take up to 10 minutes or more if the sky view is partially blocked.)  the
following trouble-shooting procedures should be undertaken to isolate the fault:

1) Disconnect the GPS antenna cable connector from the Gemini radio and check for + 5 VDC

on the center pin of the GPS antenna connector on the radio using a DVM. If the voltage is
present, do not reconnect the cable and proceed to step 2.

2) With the DVM, measure resistance between the shell and the center conductor of the GPS ca-

ble, resistance should be between 100 and 300 Ohms, if it measures open or short circuit the
GPS antenna is either a passive antenna which is the WRONG type, or a defective active an-
tenna, replace with a known good active antenna.

3) Connect the new antenna to Gemini and wait about three minutes for the POSITION

ACQUIRED indicator to start flashing on Gemini, if not, the Gemini radio or its GPS receiver
is defective.

Summary of Contents for Gemini PD

Page 1: ...Service Manual version 0 03 PRELIMINARY The entire contents of this manual and the Radio Service Software described in this manual are copyright 1998 by DATARADIO Inc Copyright DATARADIO Inc November...

Page 2: ...RONT REAR PANELS 2 2 1 1 LED Indicators 3 2 2 DTE PORT INTERFACE 3 2 2 1 RS 232 Interface Signal Levels 3 3 ADJUSTMENTS AND MAINTENANCE 4 3 1 OVERVIEW 4 3 1 INTENDED AUDIENCE 4 3 2 EQUIPMENT REQUIRED...

Page 3: ...ii What s New in Version 0 02 GPS Diagnostics procedure History Version 0 1 First preliminary version Version 0 2 Unit specification revised Typo correction...

Page 4: ...arious RS 232C interface signals Most user equipment as well as PCs are wired as DTE See also DCE GCU Gemini Control Unit board Gemini PD High specs mobile radio modem PD Parallel decode HDX Half Dupl...

Page 5: ...tic Vehicle Location AVL Using a GPS receiver determines posi tion speed and direction of fleet mem bers The Gemini PD is made up of a main transceiver and a auxiliary receiver for Parallel Decode PD...

Page 6: ...Technical Support for service in formation before returning equipment A Technical Support representative may sug gest a solution eliminating the need to return equipment 1 6 1 Factory Repair When retu...

Page 7: ...om Gemini PD hand shaking 9 AUX auxiliary input to Gemini PD panic line input port 3 It may be activated by dry contact pull up to the port s DSR output It may also tolerate user pull up to external 1...

Page 8: ...ments 3 4 1 Preliminary Verification Before performing any adjustment verify the per formance of the unit as shown in the Table 1 Important note Before proceeding make sure that the service monitor ha...

Page 9: ...sing RSS adjust TX deviation 4 Set the service monitor to generate a 80 dBm signal on the selected receive frequency The signal should be modulated with a 1 0 kHz tone Open the top cover to access the...

Page 10: ...ps screw from the unit top cover 2 Remove the top cover by lifting it from the rear 3 Slide the cover out of the case 24 23 2 1 J400 13 6Vdc Power connector Main Antenna connector Aux Receiver Antenna...

Page 11: ...ken to isolate the fault 1 Disconnect the GPS antenna cable connector from the Gemini radio and check for 5 VDC on the center pin of the GPS antenna connector on the radio using a DVM If the voltage i...

Page 12: ...urrent at 13 6 VDC 15 A TX RX separation 5 MHz typical Nominal Dimensions 7 050 D x 6 000 W x 2 0000 H Weight 3 5 lbs RF input output Impedance 50 ohms nominal RF connector Main TX RX mini UHF female...

Page 13: ...ION Interface EIA RS 232C Operation Simplex half duplex Data rates 4800 b s 9600 b s 19200 b s Modulation type DRCMSK DRCMSK DRCMSK Packet Error Rate for 1 error better than 110 dBm at 9600 b s half c...

Page 14: ...120 10503 201 ii T 96S Technical Manual...

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