2408LT Standalone L-Band Fiber Optic Transmitter
Revision
1.5
Page -
9
5. USER
CONTROLS
User controls are located behind the two removable hole plugs on the front of the unit. These plugs are
threaded and may be removed and installed with a Philips head screwdriver. When installing, ensure that
the plugs are snug so as to prevent water/dust ingress, but do not over tighten and distort the rubber
washer.
5.1.
GAIN ADJUST
Gain adjustment is via a 16 position rotary switch located behind the GAIN ADJUST hole plug. The switch
itself is marked 0-9 and A-F, and may be rotated using a small Philips screwdriver. Each step on the
rotary switch represents a 2 dB gain change, with position 0 being AGC mode. AGC will maintain the
output of the 2408LT at a constant level even if the input signal level changes, but remains within the AGC
hold range.
Switch Position
Function
0
AGC
1
Manual Gain 2 dB
2
Manual Gain 4 dB
3-F
Manual Gain 6 dB to 30 dB in 2dB steps
Table 5-1: Gain Adjustment Switch
"
If conducting frequency response sweeps, both the 2408LT and the companion receiver
should NOT be an AGC mode and should be set to a manual gain value.
5.2.
LNB MODE
The 2408LT has the ability to inject 22 kHz tone and the DC voltage supplied by the connected power
supply into the cable that is connected to the RF input. This allows both powering of the LNB as well as
control of the local oscillator. Adjustments are made via a 16 position rotary switch located behind the
LNB MODE hole plug. The switch itself is marked 0-9 and A-F, and may be rotated using a small Philips
screwdriver.
Switch Position
LNB Power
22 kHz
0
OFF OFF
1
DC PASS
OFF
2
DC PASS
ON
3
13 VDC
OFF
4
13 VDC
ON
5–F
OFF OFF
Table 5-2: LNB Mode Switch
If the LNB PWR LED is on or flashing, there will be DC voltage for LNB power at
the RF INPUT connector. This can damage some test equipment. The user can
turn off the LNB power by switching LNB MODE switch to the Off position.
