Tektronix 2715, Руководство пользователя

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Dedicated Controls
4–6
2715 User Manual
3. Press [SPAN/DIV] [1] [0] [0] [X] to set the span to 100 MHz/div.
4. Press [REF LEVEL] [3] [8] [ ] [8] [Y] to set the reference level to
38.8 dBmV.
5. Press RES BW [AUTO].
6. Turn the FREQ/MKRS knob a few clicks clockwise.
Each click of the knob increases the center frequency by 2.0 MHz.
7. Turn the FREQ/MKRS knob counterclockwise, and the center frequency
decreases by the same amount.
8. Reduce the span to 20 MHz/div.
9. Turn the FREQ/MKRS knob a few clicks clockwise.
The spectral display appears to move sideways at about the same rate as it
originally did. However, it is now moving only 0.4 MHz per click. We call
this visual behavior constant rate tuning. It occurs because the knob normally
changes the center frequency at 0.02 of the span/div per click.
2
Obviously, it
would take 250 clicks to change the frequency by 100 MHz at 20 MHz/div.
The knob remains active whenever the 2715 is in the spectral display mode.
Arrow Keys.
The arrow keys can also be used to change the normal center or start
frequency as discussed in the following example:
10. Press [
y
] adjacent to [CHAN/FREQ].
The frequency changes by channel allocation width of the currently selected
channel table (6 MHz for the STD, HRC, and IRC channel tables).
If you had previously selected a channel by entering a frequency value that is not
centered about the channel allocation width, the first increment will move the
center frequency to the center of the next channel. Subsequent increments then
default to the channel allocation width.
The up arrow selects the next channel, and the down arrow selects the previous
channel. This means that even though the 2715 is in the CATV mode, you can
increase and lower the center frequency by the channel allocation width using the
up and down arrows. You can then fine-tune the center frequency using the
FREQ/MKRS knob.
The keys remain active whenever the 2715 is in the spectral display mode.
2
In MAX SPAN the indicated frequency changes alternately by 3 or 4 MHz and as a
percent of the Resolution BW in ZERO SPAN. See Selecting the Tuning Increment on
page 6–21 for a description of how you can change the tuning rate.