2070-6A Manual
10
2070-6Asm v2 Standard Manual A00886-A.doc
both frequencies are equal distant
from their nominal values.
2)
Output amplitude. Sets the output
amplitude of the Modem. It is factory
set to 0 dB but can be adjusted to +10
dBm.
3)
Symmetry. This adjustment varies the
slicing level of the demodulator. If
correctly adjusted, an alternating bit
pattern will have a 50% duty cycle at
the RXD output.
AMPLITUDE ADJUSTMENT
To set the Output amplitude you will
need the following equipment:
1.
A 600 Ohm load that will mate to the
C2 and C20 connector. The 600 Ohm
Load is connected to pins “C” and
“E” of the connector.
2.
A TRMS meter or oscilloscope
capable of measuring a 20 kHz signal
accurately.
3.
Screw driver for adjusting the
Potentiometers.
Mount the load on the C2 or C20
connector and connect the meter or
oscilloscope across the load. Make sure
the Modem is set for Full Duplex
operation. Output an alternating bit
pattern to the Modem from the 2070 and
measure the amplitude with the meter.
Adjust the amplitude with the
Potentiometers marked “AMP A” and
“AMP B”.
The voltage read on the meter should be
0 dB or 0.775 V. The Oscilloscope’s
pattern should be about 2.2 V p-p.
FREQUENCY ADJUSTMENT
Use the same load as above and connect a
frequency counter across the Load. You
need to be able to generate Mark and
Space signals to the 2070-6A to check
the frequency.
Send a Space signal to the 2070-6A
section being checked. The frequency
indicated should be 2200 Hz +/- 1%.
Send a Mark signal to the Modem and
verify that the frequency shown on the
frequency counter is now 1200 +/- 1%.
If the frequency needs to be adjusted, The
Potentiometer marked “FREQ A or
FREQ B” should be adjusted with a
continuous Mark or Space signal being
sent to the 2070-6A.
SYMMETRY
Connect an oscilloscope to RXD A or
RXD B depending on whether the “A” or
“B” section is being checked. Set the
modem for “Half” Duplex operation local
echo on (switch 5 off). Send an
alternating bit pattern to the Modem.
(RTS needs to be on for all of these
tests). Make sure that you send 8 ms of
MARK before the alternating bit pattern
so that Carrier Detect will turn ON!
Check that the CD LED is ON. The
waveform should have a 50% duty cycle.
The “SYM A or SYM B” potentiometer
can be used to adjust the symmetry.
TROUBLESHOOTING
The 2070-6B is a fairly complex Modem
with hundreds of parts. This makes this
Modem hard to troubleshoot for the
