RFL 9780 RFL Electronics Inc.
April 8, 2003 4-14 (973) 334-3100
4.8.3 RECEIVER
After the transmitters at each end of the line have been setup, the receive portions of the 9780 must be
adjusted for the actual receive signal level. There is a coarse (attenuator) and fine (level) adjustment
for the receive level.
4.8.3.1 Input Attenuator
Adjust the input attenuator as follows:
1. Set the input attenuator (J2 on the RF Interface Module) to “50 dB”.
2. With the system in place and the far end transmitting a guard signal (either 1 W or 10 W), measure
the receive level using a FSVM. (The FSVM must be set to frequency being transmitted by the far
end at the time of measurement, including any active frequency shifts.) The level should be
measured at the receive test points on the hybrid module if supplied, or at the rear connector if there
is no internal hybrid.
3. Using Table 4-3, determine the appropriate input attenuator setting and configure the RF Interface
Module accordingly.
Table 4-3. Input Attenuator settings, RFL Interface Module
Input Range at Full Power
(Adjust R13 for 200mVrms
@ TP10)
Input Range at 1/10 x Full Power
(Adjust R13 for 63.3mVrms
@ TP10)
Jumper J2
(attenuation)
Jumper J3
(gain)
5 - 15 mVRMS 1.5 - 5 mVRMS 0 dB HI
15 - 75 mVRMS 5 - 25 mVRMS 0 dB LO
75 - 150 mVRMS 25 - 50 mVRMS 10 dB LO
150 - 500 mVRMS 50 - 150 mVRMS 20 dB LO
0.5 – 1.5 VRMS 150 – 500 VRMS 30 dB LO
1.5 - 5 VRMS 0.5 – 1.5 VRMS 40 dB LO
above 5 VRMS Above 1. 5 VRMS 50 dB LO
4.8.3.2 Input Level Adjust
Using the Frequency Selective Voltmeter, measure the signal at TP10 on the RF Interface module. If
the received guard is 1/10 the trip level, adjust R13 to obtain 63.3 mVrms at TP10. If the received
guard is the full trip level (no trip boost), adjust R13 to obtain 200 mVrms at TP10.
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