Transmitter Alignment
31
MT-3 FM Transmitter Mainboard Instruction Manual
IM20-MT3TXMN
trouBleSHootInG
Balanced Input test
1.
Connect an Audio Generator set for a 1.8 kHz tone @ +10 dBm output to the Balanced Input
(P1-1 and P1-2). The Waveform Levels Table below (see Table 2) indicates expected levels
and waveforms for various measurement points.
2.
Change the Audio Generator settings for a 1 kHz tone @ +10 dBm output. Confirm the
waveforms and levels using the Waveform Level Table below.
3.
Repeat for the various audio frequencies and levels and compare with the levels in the table
below.
TABLE 2: Waveform Levels
Test Point
Limiting Test
Std Level
Mic Test
Subtone
measured @
1.8 kHz @ +10 dBm
1 kHz @ -8 dBm
1 kHz @ -10 dBm
100 kHz @ -18 dBm
tP3
5.2 V P-P
3.8 V P-P
n/a
n/a
tP12
n/a
n/a
3.8 V P-P
n/a
tP10
6.5 V P-P
4.9 V P-P
4.8 V P-P
1.1 V P-P
tP5
2.4 V P-P
1.3 V P-P
1.9 V P-P
0.4 V P-P
Ju6
2.8 V P-P
1.7 V P-P
1.8 V P-P
0.4 V P-P
*tP8
1.5 V P-P nB
0.9 V P-P nB
0.9 V P-P nB
0.2 V P-P nB
3.0 V P-P wB
1.8 V P-P wB
1.8 V P-P wB
0.4 V P-P wB
*
These values will differ depending on the oscillator / synthesizer model.
Section C: audio frequency response and deviation
Step Reference
Action
Desired Results
Notes
15.
AF Gen level
Set and measure.
+10 dBm
16.
Balanced Audio Input Sweep from
300 Hz
to
2.5 kHz
in
100Hz
steps.
± 5.0 kHz
Deviation should not
exceed maximum
deviation.
17.
Balanced Audio Input Apply tone.
AF Gen
1kHz
@ -18 dBm
18.
Perform AF Frequency Response from
300 Hz
to
5 kHz.
As per test sheet limits
(FIT-018)
