Specifications

4-3. TRANSMITTER FRONT PANEL ADJUSTMENTS.
NOTE:Prior to setting levels be sure transmitter is ON and set to proper frequency. See Section 3.
4-4. Level Adjustment (IF). - Determine the desired subcarrier level for your specific system.
The 450 Transmitter subcarrier level can be adjusted over the range of 25 mV to 100 mV p/p
(approx. -18 TO -30 dB, 75 ohm).
A. Level Adjustment Without Video or Other Channels. - If it is possible to set the
subcarrier level with all other signals (i.e., video and all other subcarriers) removed from the
baseband, the desired subcarrier level may be set directly using an oscilloscope or wideband AC
voltmeter. Please note that it is necessary to set the second channel within the 450 Transmitter to
the OFF status in order to use this method. If it is necessary to adjust the subcarrier level in a
"live" circuit with video and/or other subcarriers present, proceed to the method described in
Paragraph B., below; otherwise, proceed as follows:
1. Connect the INPUT BNC connector of the 450 Transmitter to a suitable 75
Ohm termination.
2. Connect the OUTPUT BNC connector of the 450 Transmitter to the measuring
instrument (either an oscilloscope or wideband AC voltmeter). If the measuring
instrument has a high impedance input (normally the case), this line should also
be terminated with a suitable 75 ohm termination.
3. Make certain that the second channel of the 450 Transmitter (whichever channel
is not now being adjusted) is set to the OFF Status.
4. Adjust the IF (subcarrier level) screwdriver adjustment on the front panel for the
proper system level.
5. The other channel may now be adjusted by reversing the ON/OFF status of the
two channels.
B. Level Adjustment With Video and/or Other Channels. - When other signals (such as
video or other subcarrier channels) are present on the baseband, it is necessary to use a measuring
instrument that can be tuned to the desired signal (such as a spectrum analyzer, frequency selective
level meter, or modulation meter with level measuring capability). Proceed as follows:
1. If the measuring instrument has a high impedance input, connect it to the
baseband signal at any convenient point after the insertion of the subcarrier
to be adjusted. If the measuring instrument has a low impedance (i.e., 75 or
50 ohm) it is necessary to connect the instrument to an isolated monitor
point in order to prevent the additional load presented by the low impedance
input from affecting the level to be measured.
450 Operation Manual Rev A Page 23 8/26/99