C-COR NA15T Series Procedures Manual - 6.0
MX0860
Revision B
Setting Up a Transmitter 19
6.0
Setting Up a Transmitter
1.
Turn the
LASER
keyswitch to the
OFF
position.
2.
Verify that the RF input levels to all transmitters are correct using a signal level meter. Refer to
Figure 5. See the appropriate specification sheet for recommended RF input levels.
Laser Warning For Sevice Group SG3b: Disconnected optical connectors may emit
invisible optical radiation. Avoid direct eye exposure to the beam. Laser light, visible or
invisible, can seriously injure eyes or even cause blindness.
Never turn on a laser transmitter if all optical connectors are not covered.
RF signal input levels in excess of +60 dBmV @ 1 NTSC channel loading can damage
transmitter components. Ensure that RF Input is less than 60 dBmV @ 1 NTSC channel
loading. Derate the maximum RF input levels according to channel loading.
You can find the maximum RF level per channel for a given NTSC/PAL channel loading
by using the following equation where n equals number of channels:
(PAL will be within 0.15 dBmV of the correct value using this equation.)
This calculation is used only to determine the input level where transmitter damage may
occur. Operation outside of the RF input level shown in the specification sheet may
degrade transmitter performance. Refer to Figure 5.
Using mismatched connectors will damage the connectors and degrade system
performance. Transmitters are available with FC/APC, SC/APC, or E2000/APC
bulkhead connectors. Ensure that each fiber has a matching connector. Refer to Figure 1
for a picture of the various optical connectors.
The following describes normal operation conditions:
When the transmitter is in the Video or CW mode, there is an RF automatic gain control
(AGC) that maintains a constant total RF power to the laser. For example, with a
recommended RF level of 24 dBmV for 79 channels, if the number of channels are
reduced by half to 40 channels, the AGC will automatically compensate by raising the
internal gain by 3 dB.
If it is desired to maintain a constant RF level, as the number of channels changes, it is
recommended that the transmitter be operated in the manual mode—this maintains a
constant RF gain in the transmitter.
DANGER
laser light
Warning
Caution
Analog Input Level (dBmv)
10
1
n
---
60 dBmv
+
log
=
!
MX0860.fm Page 19 Wednesday, August 25, 1999 1:34 PM