TN910 Codan MT-3 and IFR COM-120 Test Procedures
MT-3 Radio Systems
TECHNICAL NOTES
TN910 Rev 5-0-0 May 14Page 12 of 16
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Distortion:
Transmitter audio distortion is typically less than 2.0 %. If transmitter distortion is greater than 2.0%, the transmitter
Audio Processor may need re-tuning. Refer to the Instruction Manual or Technical Note for audio processor tuning
procedures.
RF Power:
RF power output should typically be between 0.5 to 3.0 Watts (Lowband VHF), 2.0 to 8.0 Watts (Highband VHF)
or 0.5 to 8.0 or 2.0 to 8.0 Watts (UHF 400 MHz). Adjust R48 (Lowband VHF) or R7 (VHF/UHF) in the Transmitter
Amplifi er section to change the RF output power.
Connect the transmitter to the power amplifi er (if used) and measure the RF power output of the amplifi er. The
Codan 30 Watt Amplifi er’s RF power output can be changed by adjusting the transmitter (exciter) RF power output.
Do not exceed power amplifi er input levels. Higher power amplifi ers typically have a fi xed RF power input level and
RF power output level.
Frequency Stability:
Transmitter frequency stability is typically ± 1 ppm.
Transmitter Deviation Levels:
Transmitter deviation is typically ± 60% maximum deviation (±3.0 KHz wide / ±1.5 KHz narrow) for an audio frequency
of 1.0 KHz at -8.0 dBm audio level input.
To check the transmitter maximum deviation level, highlight AF GEN OUT and select ZOOM. Enter an audio level
of 2.50 Vp (1.767 Vrms or +7.2 dBm). Ideally the audio level should be set at +10.0 dBm, but the IFR COM-120
is not capable of higher than 2.50 Vp audio level (the difference between the ideal +10.0 dBm and +7.2 dBm is
neglible for this test). Enter an audio frequency of 300.0 Hz and increase the 300.0 Hz sine wave up to 3400.0 Hz
in increments of 100.0 Hz. Monitor the analog meter in the top right corner and check that the transmitter deviation
does not rise above ± 5.0 KHz wide or ± 2.5 KHz narrow at any time.
To check the transmitter subtone input level highlight AF GEN OUT and select ZOOM. Disconnect the AUDIO/
DATA GEN OUT from the Tx Balanced Audio Input connector and connect it to the Tx Subtone Input 1 connector.
Enter an audio level of 0.14 Vp (0.098 Vrms or -18.0 dBm). Enter an audio frequency of 100.0 Hz. Hit RETURN
to return to the RECEIVE window, then set the IF BW at 15 KHz. Highlight LINE and select CONFIG, then set the
MOD METERS LOW PASS FILTER for 300 Hz. Transmitter subtone deviation is typically ±0.50 KHz wide / ±0.35
KHz narrow for -18.0 dBm audio level input.
If transmitter deviation is off by more than ± 0.15 KHz deviation, the transmitter over-deviates, or the subtone
deviation is off by more than ± 0.10 KHz, the transmitter Audio Processor may need re-tuning. Refer to the Instruction
Manual or Technical Note for audio processor tuning procedures.
This product has been discontinued and is no longer manufactured by Codan Radio Communications
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