Aeroflex 2948B Betriebsanleitung PDF herunterladen (Seite 84)

LOCAL OPERATION

3-30

Marker

A variable marker can be displayed, indicated by a fine dotted vertical line, with a read-out of the

marker values displayed at the bottom of the screen. The marker reading provides two values:

The absolute RF power level at the marker position (not the level relative to the

Ref Level).

A time difference of the position of the marker relative to the trigger point.

If the marker, the

Mkr legend and the relevant readings are not displayed, press the [Marker] key.

They will appear at the bottom of the screen with the

Mkr legend highlighted. The position of the

marker along the time axis of the display can be adjusted using the variable control.

When the marker is displayed and the

Mkr legend highlighted, pressing either the

[Ref Level] key or the [Trig Level] key will highlight the appropriate legend and transfer

the variable control operation from the marker to the highlighted function.

When the marker is displayed and the

Mkr legend highlighted, pressing the [Marker] key

will remove the marker and its readings from the display.

When the marker is displayed but the

Mkr legend is not highlighted, pressing the

[Marker] key will transfer the variable control operation to the marker, and highlight the

Mkr legend.

Trigger level

The transient capture operation is started by the signal level passing through the set Trigger Level.

The set Trigger Level is relative to the Ref Level (top of display). This is set by pressing the [Trig

Level] key to highlight the Trigger Level legend, then either entering a new value using the data

input keys or by using the variable control. The Trigger Level can be set to any point within the

dynamic range of the current display.

Positive or negative triggering

The transient capture operation can be initiated by either a rising or falling signal. Repeated

presses of the [+/- Trig] key alternates the selection. The state of the current setting is shown as

either +ve edge or -ve edge.

Pre-trigger display

The user can select the proportion of the display given to pre-trigger activity. Repeated presses of

the [Pre Trig] key will step through

0 %, 25 %, 50 %, 75 % and 100 % values. 0 % will cause the

display to commence (on the left of the screen) at the time of trigger,

50 % will place the trigger

point center screen with pre-trigger levels shown to the left and post-trigger levels shown to the

right while

100 % will cause the display to finish (on the right of the screen) at the time of trigger.

25 % and 75 % will produce displays with these proportions of pre-trigger visible. The trigger

point is indicated on the display by a medium pecked line.

Transmitter frequency

The frequency of the transmission to be analyzed can either be set manually or transferred from

the previous test mode used.

When the transient analysis function is accessed, the transmitter frequency set in the Tx TEST

mode is taken as the transmitter frequency for analysis.

If the SPEC ANA mode is accessed and the span changed to use a new center frequency, this will

become the new transmitter frequency for the Tx TEST mode and therefore the transmitter

frequency for the transient analysis function.

Time scale

The time scale of the display is adjustable from 50 µs/division (500 µs full scale), to 5 s/division

(50 s full scale). Repeated presses of the [ D ] key will progressively increase the time/division in

a 1, 2, 5 sequence. Using the [ C ] key will similarly cause the time/division to decrease.

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Aeroflex 2948B Betriebsanleitung Seite 84

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