Geräte Informationen

Cushman Electronics Inc. CE-21 Level Meter
Hersteller:
Cushman Electronics Inc.
Modell: CE-21
Datum: 1972
Kategorie: Messgeräte
Gruppe: Level Meter
Beschreibung: Frequency Selective Level Meter
Informationen:
                                    The CE-21 Frequency Selective Level meter is used to measure
power levels of signals at up to 1800 voice-channel
frequencies in telephone communications systems between 4
kHz and 9.1 MHz. (See figure 1-1. )

To tune the instrument, the frequency of the desired channel
is dialled in on a lighted display with five frequency
selectors, which have a resolution of 100 Hz.

Depending on whether the instrument is to be connected to a
balanced or unbalanced line, the appropriate condition is
selected with the BAL/UNBAL switch. The input to the CE-21
can be obtained by
bridging the line or by providing termination appropriate to
the line impedance. When the TERM/BRDG switch is placed in
TERM, the input impedance can be selected with the
push-button INPUT selector (75, 124, 135, or 150fi). When
the TERM/ BRDG switch is in BRDG, the input impedance is
20kΩ for balanced lines and 10kΩ for unbalanced lines.

Calibration of the CE-21 is semiautomatic and is performed
by pushing a single button which automatically switches the
input circuit to 75Ω, provides an accurate-level (0 dBm)
internally-generated calibration signal, presets the
frequency of the 1st LO, and adjusts the attenuators for a 1
MHz, 0 dBm input. The meter is then manually set to zero
which calibrates the instrument for all available input
impedances at all signal frequencies within CE-21 range.

After calibration and with an input signal connected to the
instrument, two front-panel level selectors are used to
attain a zero reading on the meter. There are two displays
so that one can be used to set the level of a signal with a
certain frequency (for instance to the transmission level
point of a pilot tone), while the other is used to establish
the level of a second signal. The second level display will
thus give a value that is relative to the level indicated on
the first display. Either level display can be used to set
the reference, andbothhave two knobs which permit level
selection in 10-dB and 1-dB steps. The left display is
labeled "dBl" and can be adjusted to read from -79 dB to +19
dB; the one on the right is labeled "dB2" and can be
adjusted from -99 dB to -0 dB. As is indicated on the front
panel between the two level displays, the measured level in
dBm at meter zero (0) is the algebraic sum of the dBl and
dB2 readings. When this sum exceeds -99 dBm, a -99 dBm
EXCEEDED light comes on to warn the operator that the range
of the instrument is being exceeded.

Since it is inherently impossible to provide both lowest
distortion and lowest noise level at the same time in any
instrument, provision has been made for selection of either
low-distortion or low-noise operation of the CE-21.
Meter readings can be taken from -20 dBm to +2 dBm, or, on
an expanded scale, from -2 dBm to +2 dBm. When the expanded
scale has been selected, the light adjacent to the meter
switch is lit. When the meter -on either scale- indicates a
reading other than zero, this reading must be added to the
algebraic sum of dBl and dB2, but the quantity indicated on
the meter is not included in the -99 dBm that should not be
exceeded. Thus, level measurements are possible from -
119dBm (meter reading = -20 dBm, dBl + dB2 = -99 dBm) to +21
dBm (meter reading = +2 dBm, dBl + dB2 = +19 dBm).
The BANDWIDTH (NOISE) selector provides a choice of narrow
(200 Hz) bandwidth for separation and level readings of
suppressed carriers and pilot tones, or wide (2.3 kHz)
bandwidth for noise readings. When the broad bandwidth is
selected, audio signals can be monitored over the built-in
speaker. The audio selector lets the operator select AM,
lower sideband (LSB), or upper sideband (USB). A volume
control is also provided.

On the front panel, under BANDWIDTH, the word NOISE appears
in blue, and, under "2.3 kHz", "1.74 kHz" is shown, also in
blue. The two numbers relate the bandpass of the CE-21 to
the concept of Equivalent Noise Bandwidth and the
C-message-weighted curve.

As is common knowledge in the telephone industry, the
C-message-weighted (Cmw) curve represents the response curve
of all telephone handsets used in the United States.

The concept "Equivalent Noise Bandwidth" refers to a
perfectly rectangular curve which bounds an area equal to
the area bounded by a Cmw curve. It has been shown that when
the area bounded by a Cmw curve is found by graphic
integration, the result is approximately equal to an area
bounded by a curve with a uniform width of 1. 74 kHz. It is
now almost universally accepted that any bandpass
represented by a curve which bounds an area equal to that
bound by a 1. 74 kHz rectangular curve permits noise
measurements that are, for all practical purposes, the same
as would be obtained with a bandpass curve identical to the
Cmw curve. Thus, when, on the front panel of the CE-21, the
broad bandwidth is specified as "2.3kHz,

1.74	kHz", the CE-21 bandpass curve is

2.3	kHz wide at the -3 dB points, and the area bounded by
this curve approximately equals the area bounded by a 1.
74-kHz-wide rectangular curve.

A commonly used measurement unit for noise is dBrnC (dB
referred to noise, C-message weighted), where 0 dBrnC = -90
dBm. When measuring noise levels with the CE-21, a reading
in dBrnC measurement units can be obtained by-adding 90 to
the dBm reading.

By using the CE-22 Tracking Signal Generator in conjunction
with the CE-21, frequency tests can be made on transmission
lines or circuits of telecommunications systems. The CE-22
provides a stable signal source the frequency of which is
controlled by the CE-21. Thus, the CE-22 tracks exactly; it
contains an automatic level control, and it provides the
capability of presetting its signal level from -70 dBm to
+10 dBm, with a resolution of . 01 dB.

Another companion unit for the CE-21 is the CE-23 Spectrum
Display, which provides simultaneous high-resolution
displays of signals that are being measured with the CE-21.
In addition, there is also
available the CE-26 Signal Generator, which has all the
features of the CE-22 Tracking Signal Generator, with the
additional capability of generating its own signal. The
Frequency Synthesizer used in the CE-26 is virtually
identical to the one used in the CE-21. In contrast to the
CE-22 and the CE-23, which must be used with the CE-21, the
CE-26 can be used independently.

Folgende Handbücher sind hierfür verfügbar:

Cushman Electronics Inc. -- CE-21 -- Service- und Bedienungsanleitung
Dateiname: Cushman-9210-Manual-Page-1-Picture
Dokumenttyp: Service- und Bedienungsanleitung
Seitenanzahl: 156
Dateigröße: 115.61 Mbytes (121225224 Bytes)
Sprache: Englisch
Revision:
Dokument-ID/Nummer:
Datum: 01 August 1972
Qualität: Gescanntes Dokument, teilweise schwer oder teilweise nicht zu lesen.
Upload Datum:
MD5: 226f232452d2cbf4a46e3725871def9f
Downloads: 12 seit dem 07 August 2017
Informationen:
Serial Numbers 146 and up

SECTION 1 GENERAL INFORMATION

1.1	Description
................................................1-1

1.2
Accessories................................................1-3

SECTION 2 INSTALLATION

2.1	Unpacking and
Inspection..................................2-1

2.2	Installation
Procedures....................................2-1

2.2.1	Power Requirements ..........................2-1

2.2.2	Grounding Requirements ......................2-1

2.2.3	Warm-up Requirements........................2-1

2.2.4	Conversion to Rack Mount......................2-1

2.3	Preparation for Reshipment ..............................2-1

2.4	Service or
Repair..........................................2-2

SECTION 3 OPERATING INSTRUCTIONS

3.1	Controls and
Indicators....................................3-1

3.2	Operation
..................................................3-5

3.2.1	Turn-On........................................3-5

3.2.2	Calibration......................................3-5

3.2.3	Operation for Signal Level Measurement . . .	3-6

3.2.4	Operation for Noise Level Measurement . . .	3-7

SECTION 4 THEORY OF OPERATION

4.1	Functional
Description....................................4-1

4.2	Circuit
Description........................................4-1

4.2.1	Input Selection..................................4-1

4.2.2	Hi-Z Attenuators No. 1 and No. 2 ............4-2

4.2.3	Attenuator Control Logic........................4-2

4.2.4	Balanced Input Amplifier ......................4-6

4.2.5	15-dB Attenuator................................4-7

4.2.6	Low-Pass Filter................................4-7

4.	2. 7 First Mixer....................4-7

4.	2. 8 First IF Amplifier..................4-8

4.2.9	Second Mixer....................................4-8

4.2.10	Second IF Amplifier .......................4-8

4.2.11	Meter Amplifiers................................4-9

4.2.12	Audio Amplifiers................................4-10

4.2.13	Frequency Synthesizer..........................4-11

4.2.14	Voltage-Controlled Crystal Oscillator..........4-15

4.2.15	Calibration Amplifier............................4-16

4.2.16	Power Supply....................................4-17
SECTION 5 MAINTENANCE
5.1
General......................................................5-1

5.2
Fuses........................................................5-1

5.3	Adjustments.........................................5-2

5. 3.1 Test Equipment Required........................5-2

5.3.2	Power Supply Voltages..........................5-2

5.3.3	Master Oscillator Frequency....................5-3

5.3.4	First Local Oscillator..........................5-3

5.3.5	Second Local Oscillator ........................5-4

5.3.6	IF Amplifiers..........................5-5

5.3.7	Meter Amplifiers................................5-6

5.3.8	Calibration Amplifier............................5-6

5.4	Performance
Verification..................................5-6

5.4.1	Second Mixer to Meter Gain Check..............5-6

5.4.2	RF Casting Assembly Gain Check..............5-7

5.4.3	First Local Oscillator Check....................5-7

5.4.4	First IF Check..................................5-7

5.4.5	RF Casting Internal Signal Levels Check . . .	5-8

5.	5
Troubleshooting............................................5-8

SECTION 6 SCHEMATICS, PARTS LISTS, AND COMPONENT LAYOUTS

6.1	Schematics, Parts Lists, and Component Layouts ....	6-1

6.2	Reference
Designators......................................6-2
6.3	Abbreviations............................6-2
6.3.1	Front Panel......................................6-3

6.3.2	Impedance Selector..............................6-11

6.3.3	Main Chassis....................................6-15

6.3.4	Master Oscillator/Divide-by-N/Reference

Divider........................................6-19

6.3.5	Meter Amplifiers/Audio Amplifiers............6-27

6.3.6	Voltage-Controlled Oscillator..................6-33

6.3.7	Sample-and-Hold/Calibration Amplifier ....	6-41

6.3.8	Second IF Amplifier/200 Hz Bandpass Filter. .	6-49

6.3.9	Power Supply Rectifiers........................6-55

6.3.10	Attenuator Control Logic........................6-59

6.3.11	Power Supply Regulators........................6-65

6.3.12	Second IF Amplifier/2. 3 kHz Bandpass Filter .	6-71

6.3.13	RF Housing......................................6-75

6.3.14	First Mixer......................................6-79

6.3.15	Low-Pass Filter.................6-83

6.3.16	First IF Amplifier..............................6-87

6.3.17	Second Mixer .........................6-93

6.3.18	Hi-Z Attenuator No. 2 ..........................6-97

6.3.19	15-dB Attenuator................................6-101

6.3.20	Voltage-Controlled Crystal Oscillator..........6-105

6.3.21	Balanced Input Amplifier . .....................6-109

6.3.22	Hi-Z Attenuator No. 1 ..........................6-115

6.3.23	Rear Panel......................................6-119
Cushman-9210-Manual-Page-1-Picture
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