Tektronix 2715, Руководство пользователя

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Getting Started
2715 User Manual
2–17
Suppose that you want to view just a single harmonic and the 30 MHz band to
either side of it. You can do this by setting the span to 6 MHz/division. This is
not a value obtainable with the arrow keys, but you can to get it in the immediate
entry mode.
9. To set the span/division to a predetermined value, first press [SPAN/DIV] to
place span in the immediate entry mode.
Notice that the abbreviation SPAN appears at the left center of the screen.
The SPAN indicator tells you that you can enter the span/div directly from the
keypad. This is done by keying in a permissible value followed by an appropriate
terminator key.
10. Press [6] to set the span/div to 6 MHz.
Any number you type appears on screen to the right of SPAN. If you make a
mistake, you can correct it by repeatedly pressing [BKSP] (the backspace
key) until the incorrect number disappears and then entering the correct
value.
11. Press [X] after the correct number has been entered.
This key can represent units of MHz, ms, or mV. Because you selected an
entry mode that requires a frequency, the 2715 correctly interprets the
currently displayed entry as 6 MHz. If a time or voltage unit had been
required, the 2715 would have interpreted your entry as 6 ms or 6 mV,
respectively.
The span now is set to 6 MHz, and the ninth harmonic of the calibrator signal is
centered on screen at 900 MHz. You may have noticed that the resolution
bandwidth changed to 1 MHz. This demonstrates the AUTO resolution
bandwidth selection mode of the 2715. The spectrum analyzer reduces its
resolution bandwidth as you reduce the span/div, so the resolving power of the
instrument automatically increases as you look at the spectrum more closely.
To look at the calibrator signal fundamental, you must change the center
frequency. The spectrum analyzer provides three direct methods of doing so,
each appropriate under different circumstances.
12. Press [
b
] to the right of [CHAN/FREQ] twice.
Notice that the center frequency readout now indicates approximately
894.0 MHz. The frequency arrow keys change the center or start frequency
by the same as the span/div, but you can change the tuning rate. See
Selecting the Tuning Increment on page 6–21. You could continue pressing
[
b
] until the correct frequency is reached, but this would require a large
number of presses.