P.A.M.S.
Technical Documentation
NME–2A
Troubleshooting Instructions
Page 18
Original 08/97
1.3. Modulator and LO signal generation:
Via PCLocals select local mode, RF control, TX mode, Power level 10
(23 dBm), Operation mode continuous or burst, Data type random,
Continuous mode channel 60, Channel 60, Monitoring channel 1.
Measure with oscilloscope probe and spectrum analyzer.
– Output of modulator on T802: –10 dBm ±5 dB.
– Input to the modulator consist of three discrete frequencies, where the
wanted is the lowest frequency, and at a level about 15 dB higher than
the other two. Absolute level about –10 dBm for the wanted signal.
– Check the LO generating mixer (UHF TX and VHF RX PLL), the ampli-
fier and the filter.
– UHF LO: 5 dBm ±5 dB, 1014 MHz
– VHF RX PLL: –5 dBm ±5 dB, 116 MHz
– Check the modulating input, balanced pairwise for I and Q, about 1
Vpp for every signal, d.c. at 2.4 V.
– Check the power and enable to the modulator.
– Check the UHF and VHF synthesizers.
2. Modulation spectrum:
Select I and Q TUNING in PCLocals. Measure with spectrum analyzer on
the antenna connector (up to 40 dBm output!). Span 0.2 MHz, resolution
BW 10 kHz, video 10 kHz, sweep time 0.5 sec.
– Relative to the mainslope the signal at +67 kHz should be more than
30 dB down, and the signal at +135 kHz should be more than 50 dB
down.
– If not tune the offset values, I and Q d.c. offset to change the signal at
+67 kHz, phase and amplitude offset to change the signal at
+135 kHz.
To Next Page
Loading...
