120 20191-001
Paragon-III
Technical Manual
26
Multiple channels (adjusting as shown for single channel above):
1.
T885 Adjust the VCO loop to 10V using the middle frequency channel.
2.
All channels should lie within the upper and lower limits of respectively
All channels should lie within the upper and lower limits of 16V and 3V for the T885.
5.2.2.3 Front-End Alignment
1.
IFR COM120B settings:
a)
Connect a 3 feet long double shielded cable (N-M to BNC-M) between the IFR T/R output and the
receiver antenna connector.
b)
Select the generator mode (GEN button) and set to the main receiver channel frequency
c)
Select and turn-on GEN2
d)
Set the FM Deviation to ±3kHz (full channel) or ±1.5kHz (half channel) using 1KHz sine
e)
Select SINAD meter
f)
Use a X1 scope probe connected to SINAD input and monitor the Discriminator O/P on the back-
plane at SK1 pin 6 (RX-audio1). Alternately, it is also possible to monitor at the receiver I/O Pad
P207 (T885).
2.
Adjust the helical resonators for best SINAD: #H400, #H401 and #H900 (T885).
3.
Continually decrease the RF level to reach 12dB SINAD, then re-do step 2) & 3) again. The absolute
minimum requirement level to reach is -108dBm (typical level is -109 to -110 dBm)
4.
Perform the SINAD linearity tests described in paragraph 5.2.2.4. If it fails to pass the requirement,
contact your Dataradio technical support.
WARNING: Do NOT attempt to re-tune the IF stages
(I.e. L300 and L301 for T885)
These adjustments do not need to be re-adjusted after frequency re-programming. Touching these
coils will have a direct impact on the modem DSP ISI coefficient settings and may reduce signifi-
cantly the radio performances over data.
5.2.2.4 SINAD and Linearity Check
1.
Apply the following settings to the IFR COM-120:
a)
Generator mode, Output T/R, TX frequency to match the main radio RX frequency
b)
Filter set to wide band (no audio filter)
c)
Select Gen2 (Modulating tone fixed to 1KHz). All other Gen must be off.
d)
Set deviation to
±
3.0KHz for full channel or
±
1.5KHz for half channel radios.
e)
Use a X1 scope probe connected to the IFR SINAD input and monitor the Discriminator O/P on the
radio backplane at SK1 pin 6 (RX-audio1). Alternately, it is also possible to monitor at the receiver
I/O Pad P207 (T885).
2.
Lower the RF level to get a 12dB SINAD reading. Level should be better than
-
108dBm
(including ca-
ble loss).
3.
Offset the IFR TX frequency 2kHz
above
the main radio RX frequency, record the SINAD reading. It
should remain within 1.5 dB from the on frequency SINAD reading.
4.
Offset the IFR TX frequency 2KHz
below
the main radio RX frequency, record the SINAD reading. It
should remain within 1.5 dB from the on-frequency SINAD reading.
Note: If one of the above requirements is not met, try to re-tune the front-end. If still failed, contact
your Dataradio technical support.
