Description and Basic Operation of the SDA-5500 and 5510: Basic Modes of Operation
240
13
Level Adjustments
A LVL (level) soft key is used to adjust the vertical parameters of the graph.
These parameters include Max Hold, Ref Level and Scale.
The Max Hold function ensures that the highest signal over multiple sweeps
is displayed. When the Max Hold soft key is pressed, as indicated in the left
hand corner of the display, the highest signal level is displayed. The M1/M2
readings correspond to the max hold levels. As multiple sweeps are
performed, the maximum level trace will only change if new sweep levels
exceed the existing levels.
The reference level is located at the top line of the graph. The Ref Level can
be adjusted using the cursor keys or by entering a numeric value followed by
the enter key.
The scale parameter (1,2,5, & 10 dB/div) can only be adjusted with the
cursor keys. For example, if the reference level was set at 0 dB and the
scale was set at 10 dB/div the first horizontal grid line above the center
would be equal to -30 dB. Press the LVL soft key to return to the main
spectrum analyzer display.
Frequency Adjustments
Press the FRQ soft key to edit frequency range parameters of the Spectrum
Analyzer display. Use the up and down arrow keys or the numeric entry
keypad to set the center frequency. Press the Span soft key to adjust the
span frequency. The Full Span soft key can be used to set the start and stop
frequency to the full range of the unit. Press the FRQ soft key to return to the
main spectrum analyzer display.
How To Make FCC In-Channel Response Measurements
(FCC limit: + 2 dB)
The frequency response of any channel can be measured using the
Spectrum Analyzer mode. A flat signal source must be inserted at the input
of the modulator or processor. In testing a modulator, this source may be a
full field multiburst signal, or a sweeping function generator. For a processor,
a bench sweep generator or a broadband noise source may be used. The
response is monitored with the receiver in the Spectrum Analyzer mode. A 5
or 10 MHz span may be used. The “Max Hold” function is used to ensure
that the peak levels are measured at all frequencies. The scale can be set as
low as 0.5 dB/div, but you will use the appropriate scale setting to enable
display of the full response on screen. Then position the markers at the
maximum and minimum points of the display and read the delta indicated at
the bottom of the screen. The FCC requirement is a window of ±2.0 dB,
which means the delta should be < 4 dB.
To Next Page
Loading...
Need help?
General
