Microwave Data Systems MDS 4310 Installation, Operation & Field Maintenance page 78

U3
Pin 7
Figure 4-6. 9600 BPS FSK Modem; MDS P/N 03-1833A01
See Table C-1 in Appendix C for details on switch settings.
Transmit Frequency
1. Key the transmitter by raising RTS (SW1 Closed). The TXD line should be at logic
low (LED annunciator TD [TXD] off).
2. Check for correct transmit center frequency. With TXD low (SW2 Open) the
transmitted frequency should be within 100 Hz of the assigned center frequency. If
necessary, adjust the TCXO frequency adjustment (on the transceiver's
motherboard), to place it on frequency.
If Remote Maintenance is installed, use the
R
instead of adjusting the TX Frequency adjustment on the TCXO. The
M
commands increment/decrement the frequency in single steps while the
INCF / DECF
to the command. (For example:
steps out of 100.) When finished, type
Data Deviation
1. With the radio still keyed (SW1 Closed), raise TXD (SW2 Closed). This should
cause the transmitted frequency to shift by 1.6 kHz ±75 Hz either up or down.
It does not matter if the frequency shifts up or down; the way it shifts depends only
upon the phase of the modem's internal 9600 Hz clock at the instant the TXD line
changed. If the TXD line is toggled, the transmit frequency should change between
the assigned center frequency when TXD is low and 1.6 kHz on either side of center
when TXD is high. If necessary, adjust R168 on the transceiver motherboard to
obtain a 1.6 kHz ±75 Hz shift.
If Remote Maintenance is installed, set R168 to its full-clockwise position
R
and use the
M
1.6 kHz. The
steps while the
and a number to the command. (Example:
by four steps out of 100.) When finished, type
2. Toggle TXD high (SW2 Closed) until the frequency shifts opposite from above. The
frequency should shift 1.6 kHz ±75 Hz. If not, alternately adjust the TX Frequency
adjustment on the TCXO and R168 on the transceiver's motherboard, toggling TXD,
checking both the high and low frequencies for equal 1.6 kHz shifts.
Continued on next page.
MDS 05-2415A01, Rev. A
(CLOSED)
P8
commands make larger jumps by adding a space and a number
ID / DD / INCD / DECD
commands increment/decrement the deviation in single
ID / DD
INCD / DECD
FIELD TESTS & ADJUSTMENTS
S1
CONFIGURATION
8 1 OFF (OPEN)
ON
U6
U5
IF / DF / INCF / DECF
to increase the frequency by eight
INCF_8
to store the setting.
RMST
commands to set the frequency shift to
commands make larger jumps by adding a space
INCD_4
RMST
P6
commands
IF / DF
to increase the deviation
to store the setting.
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