RFL 9785 - Setting Jumpers on Rx Filter and Rx Filter Tuning

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9.6.6 SETTING JUMPERS ON Rx FILTER AND Rx FILTER TUNING
The Rx Filter has a large number of jumpers (about 100) that must be configured for proper system
operation. These jumpers allow a user to select the bandwidth, which can be either 8kHz or 16kHz,
and to tune the center frequency, which can be from 24kHz to 496kHz (the outer edges are 20kHz and
500kHz). The location of these jumpers is shown in Figure 9-22. Tuning the filter is done from the RF
Section of the NMS software.
In addition to the jumpers, the Rx filter has three tunable inductors, L1, L2 and L3. Their functions are
as follows:
L2 controls the balance of the filter (flat response at both sides of center frequency).
L1 controls the attenuation at the upper side of center frequency.
L3 controls the attenuation at the lower side of center frequency.
9.6.6.1 QUICK TUNING PROCEDURE
1. For the selected center frequency, set the jumpers as described in the RF Section of the NMS
software. Jumper locations are shown in Figure 9-22.
2. Connect a signal generator (HP3336B or HP3325A or equivalent) to J2 of the Rx Filter.
Connect a selective level meter (Wandel & Golterman SPM-32A or 33A, Rycom 6021A,
Signalcrafters 110, or equivalent) with a terminating impedance of 50 Ohms, to J3 of the Rx
Filter. Use J4 as the ground connection.
3. Set the center frequency of the test equipment (signal generator and selective level meter)
according to the selection made in Step 1.
4. Adjust inductors L1, L2 and L3 to have a minimum loss (highest voltage level) at the selected
center frequency.
For 8kHz bandwidth Rx Filters, perform steps 5, 6 and 7.
For 16kHz bandwidth Rx Filters perform steps 8, 9 and 10.
5. Check the attenuation at the selected center frequency +/- 4kHz <0.35 dBm.
Adjust L2 to have a balanced response (the same level at +4 and –4 kHz) dBm.
6. Check the attenuation at the selected center frequency +/- 12kHz.
Adjust L1 to get the desired attenuation at +12 kHz >9.5 dBm.
Adjust L3 to get the desired attenuation at +12 kHz >9.5 dBm.
7. Check the ripple between +/-3.5 kHz from the center frequency to be < 0.3 dBm.
8. Check the attenuation at the selected center frequency +/- 8kHz <0.35 dBm.
Adjust L2 to have a balanced response (the same level at +8 and –8 kHz) dBm.
9. Check the attenuation at the selected center frequency +/- 18kHz <0.35 dBm.
Adjust L1 to get the desired attenuation at +18 kHz >9.5 dBm.
Adjust L3 to get the desired attenuation at +18 kHz >9.5 dBm.
10. Check the ripple between +/-8 kHz from the center frequency to be < 0.35 dBm.
RFL 9785 RFL Electronics Inc.
May 16, 2011 9-34 (973) 334-3100