B+K precision 2165A, Instruction Manual, Page: 10 / 28

10
CONTROLS AND INDICATORS
The front panel controls of the instruments are shown in
Figures 3 through 6 and are explained below.
1. FOCUS. Beam sharpness adjustment.
2. INTENS. Beam intensity adjustment.
3. POWER (Power ON and OFF) . If power is switched to
ON position, a beam will be visible on the screen after
approximately 10 sec..
4. TR (Trace Rotation). Despite Mumetal-shielding of
the CRT, effects of the earth’s magnetic field on the
horizontal trace position cannot be completely avoided.
A potentiometer accessible through an opening can be
used for correction. Slight pincushion distortion is
unavoidable and cannot be corrected.
5. MARKER - ON/OFF switch. When the MARKER
pushbutton is set to the OFF position, the CF indicator
is lit and the display shows the center frequency. When
the switch is in the
ON position, MK is lit and the
display shows the marker frequency. The marker is
shown on the screen as a sharp peak. The marker
frequency is adjustable by means of the
MARKER
knob and can be aligned with a spectral line.
NOTE
Switch off the marker before taking
correct amplitude readings.
6. CF/MK (CENTER FREQUENCY/ MARKER)
indicator.
The CF LED is lit when the digital display
shows the center frequency. The center frequency is
the frequency which is displayed in the horizontal
center of the CRT. The
MK LED is lit when the
Marker pushbutton is in the ON position. The digital
display shows the marker frequency in that case.
7. DIGITAL DISPLAY (Display of Center Frequency/
Marker Frequency)
7-segment display with 100 kHz
resolution.
8. UNCAL. Blinking of this LED indicates incorrectly
displayed amplitude values. This is due to scanwidth
and filter setting combinations which give uncalibrated
amplitude readings because the IF-filters have not
settled. This may occur when the scanned frequency
range (
SCANWIDTH ) is too large compared to the IF
bandwidth, and/or the video filter bandwidth.
Measurements in this case can either be taken without
a video filter or the scanwidth has to be decreased.
9. CENTER FREQUENCY – Coarse/Fine. Both rotary
knobs are used for center frequency setting. The center
frequency is displayed at the horizontal center of the
screen.
10. BANDWIDTH. Selects the IF bandwidth. When the
switch is engaged, the noise level decreases and the
selectivity is improved. Spectral lines which are
relatively close together can be distinguished. As the
small signal transient response requires a longer time,
this causes incorrect amplitude values if the scanwidth
is set at too wide a frequency span. The
UNCAL LED
will indicate this condition.
11. VIDEO FILTER. The video filter may be used to
reduce noise on the screen. It enables small level
spectral lines to become visible which normally would
be within or just above the medium noise level. The
filter bandwidth is 4 kHz.
12. Y-POS. Control for adjusting the vertical beam
position.
13. INPUT. The BNC 50
Ω input of the spectrum analyzer.
Without input attenuation the maximum permissible
input voltages of ±25V DC and +l0 dBm AC must not
be exceeded. With the maximum input attenuation of
40 dB the maximum input voltage is +20 dBm.
The maximum dynamic range of the instrument is 70
dB. Higher input voltages exceeding the reference level
cause signal compression and intermodulation. Those
effects will lead to erroneous displays. If the input
level exceeds the reference level, the input level
attenuation must be increased.
14. ATTN. (ATTENUATOR). The Input Attenuator
consists of four 10 dB attenuators, reducing the signal
height before entering the 1st mixer. Each attenuator is
active if the push button is depressed.
The correlation of selected attenuation, reference level
and baseline level (noise level) is according to the
following listing:
Attenuation
Reference level Base line
0 dB –27 dBm 10 mV –107 dBm
10 dB –17 dBm 31.6 mV –97 dBm
20 dB –7 dBm 0.1 V –87 dBm
30 dB +3 dBm 316 mV –77 dBm
40 dB +13 dBm 1 V –67 dBm