TN910 Rev 5-0-0 May 14
TN910 Codan MT-3 and IFR COM-120 Test Procedures
MT-3 Radio Systems
TECHNICAL NOTES
Page 7 of 16
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Receiver and Auxiliary (AC-3E) Output Audio Levels:
The audio level adjustment can be done on both the Rx Balanced Audio Output and the Auxiliary Balanced Output
(1 and 2). The Auxiliary Balanced Output is only available on the AC-3E Control Card. The Receiver and Auxiliary
Balanced Audio Outputs are 600 ohm balanced audio outputs and will require an external 600 ohm matching load
before an accurate measurement of the audio level can be performed by the IFR COM-120.
Rx Balanced Output:
1. Ensure the receiver is turned on and the Audio Control Card is NOT plugged into the subrack.
2. Adjust the Rx Balanced Audio level adjustment (R64 the High Level Drive Adjust) for -8.0 dBm audio level (308
mVrms @ 600 ohms). If no external 600 ohm load is available, the audio level could be adjusted for approximately
585 mVrms in the IFR COM-120.
Auxiliary Balanced Output (1 & 2):
1. Ensure the receiver is turned on and the Audio Control Card IS plugged into the subrack.
2. Connect the Auxiliary Balanced Audio Output (1 or 2) from the AC-3E to the AUDIO/DATA SINAD IN input on the
IFR COM-120.
3. Adjust the Auxiliary Balanced Audio level adjustment (R13 for Aux Out 1, R56 for Aux Out 2) for 0.0 dBm audio
level (775 mVrms @ 600 ohms). If no external 600 ohm load is available, the audio level could be adjusted for
approximately 2.50 Vrms in the IFR COM-120.
To select between dBm and Vrms, highlight AF LEVEL and select ZOOM as shown in Figure 5 . Highlight the
measurement units and select Vrms or dBm (ensure that the impedance is set to 600 Ohms when selecting dBm)
as shown in Figure 6. Hit RETURN to return to the GENERATE window.
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Figure 5: IFR COM-120 Audio Level Confi guration Figure 6: IFR COM-120 Impedance Selection
This product has been discontinued and is no longer manufactured by Codan Radio Communications
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