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Gemini G3 - User Manual
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5.3 Additional test details
5.3.1 Carrier Deviations
GeminiG3 radiomodems make use of the carrier “AutoDeviation” feature. Therefore, the carrier devia-
tions in the table below are given for reference only.
Table 6 - Carrier Deviations
Carrier Modulation
SRRC4FSK
SRRC8FSK
SRRC16FSK
Tone
Tone
Tone
Network Speed
(kb/s)
Typical deviation
in kHz
(1000Hz test tone)
Network Speed
(kb/s)
Typical deviation
in kHz
(1000Hz test tone)
Network Speed
(kb/s)
Typical deviation
in kHz
(1000Hz test tone)
Full Channel (UHF) 25kHz bandwidth
32.0
± 3.7
48.0
± 4.0
64.0
± 4.1
43.2
± 4.2
Half Channel (UHF) 12.5kHz bandwidth
16.0
± 1.7
24.0
± 2.0
32.0
± 2.1
Wide Channel (700MHz) 50kHz bandwidth
64.0
± 5.3
96.0
± 6.2
128.0
± 6.5
Full Channel (800MHz) 25kHz bandwidth
32.0
± 2.4
48.0
± 2.7
64.0
± 2.9
43.2
± 3.3
NPSPAC Channel (USA - 800MHz)
16.0
± 2.4
24.0
± 2.7
32.0
± 2.9
5.3.2 GPS Test
About three minutes after ignition is turned-on, the PWR LED on the GeminiG3 unit front panel should flash
in b
linking amber on green
color at the rate of one pulse per second (1pps). This indicates that the GPS has
acquired the sky position of a sufficient number of satellites to arrive at a ground 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 Digital voltmeter (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 cable, resis-
tance 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 antenna, replace with a known good
active antenna.
3) Connect the new antenna to Gemini and wait about three minutes for the “PWR/PGM LED to start flash-
ing at a rate of 1 pulse per second
(amber on green)
on the GeminiG3 unit indicating that a position is ac-
quired. If no position acquisition occurs, the modem and/or its GPS receiver may be defective.
The User’s Interface GPS Web Pages are located starting at paragraph 4.7.4.