Introduction
The typical spectrum analyzer in use for cable
television purposes is a swept-tuned or scanning radio-frequency analyzer. This
means that instead of displaying signal amplitude as a function of time as is
done by the oscilloscope, the spectrum analyzer will use the frequency domain
as the x-axis on its graphical display.
This allows radio energy signals differing in frequency to be examined
for their proper attributes. The
technician using this field guide should already be aware of this basic
information along with the uses and limitations of spectrum analysis. The basic information presented in this
quick field guide is not meant to substitute for the proper understanding and
operation of the Tektronix® 2714 CATV Analyzer.
Indeed, the instructions assume the technician already has some familiarity
with this analyzer. Additionally, the
technician should have a basic understanding of the tests required by the
Federal Communications Commission (FCC).
The purpose of this field guide is to allow experienced technicians to
quickly perform certain required measurements without the need to search and
summarize the supplied manual. This guide is neither supplied nor
endorsed by the manufacturer of Tektronix® equipment. To use the Tektronix® analyzer for purposes other than those
outlined below, it is recommended the Tektronix® provided manual be consulted.
The finger controls on the Tektronix® spectrum
analyzer will allow the user to move and zoom (in terms of frequency and
amplitude) on the displays of the received signals of interest. Other controls
will allow certain operating parameters on the analyzers such as
"bandwidth" and "scan rate" to be changed. Properly setting the parameters will not only
increase the accuracy of measurements, but may allow anomalies to be seen that
could not be seen otherwise. Yet more
controls allow the software-driven manipulation of the previously mentioned
controls to perform automated multi-step testing.
A spectrum analyzer is a versatile testing
and troubleshooting device whose accuracy limits must be respected. The user
must be aware of the specifications of the analyzer and be able to determine if
it meets the needs for its intended purpose.
As an example, many times, the frequency display portion of a spectrum
analyzer is a reference only and not an accurate depiction of frequency. The
analyzer must have a built-in frequency counter to read actual frequency. For FCC testing, the counter must have a
high enough accuracy for that purpose. The amplitude reading is also subject to
accuracy ratings. Furthermore, some tests may require signal amplitudes to be
within a specific range to reduce the uncertainty of the result of those tests.
In all cases, refer to the owner’s manual for the specifications or consult
with the manufacturer.
Setup Instructions for the Tektronix® 2714 CATV Analyzer
For the purposes of the instruction listed
below, labels in capital letters are for menu items on the display and will be
preceded by a “Select” command. Labels
in bold capital letters are for physical buttons on the analyzer and will be
preceded by a “Press” command.
Press POWER
Allow the analyzer to warm up 15 minutes
before use.
Due to the variety of older machines in use,
the following instructions are based on analyzer firmware Version 06.05.92. The
firmware should be upgraded when the analyzer is sent in for calibration.
To check the version of firmware in use
perform the following steps:
Press UTIL in
the button grouping labeled “MENUS”
Select 4 SYSTEM CONFIGURATION
Select 9 INSTALLED OPTIONS DISPLAY
The version number (date) will read under the
INSTALLED OPTIONS
heading
Press any “MENUS” key
to exit the utility menu
To check/modify the test setup perform the
following steps:
Press CATV/APPL in
the button grouping labeled “MENUS”
If the menu heading does not read CATV MEASUREMENTS, Select 9 to leave
its current menu
Select 5 CARRIER TO NOISE to enter that menu (Select 9 MORE if
required first)
Select 5 CARRIER TO NOISE SETUP to enter that menu
If needed, Select 5 NOISE NORM’D BW, Press 4 and Press
MHz mSEC mV
on the keypad for 4.0 MHZBW
Select 0 INTERACTIVE to
place the C/N test in interactive mode
Do not select 1 AUTO as
firmware older than 01.05.95 will violate FCC parameters
Do not select 2 AUTO (PAUSE
FOR CARRIER OFF) as firmware older than 01.05.95 will violate FCC parameters
Press BSKP as
needed to return to the CATV
MEASUREMENTS menu
Select 6 HUM/LFD to
enter that menu
If needed, Select 5 POWER LINE FREQ, to toggle the line frequency to 60Hz
Press BSKP as
needed to return to the CATV
MEASUREMENTS menu
Select 5 CTB/CSO to
enter that menu (Select 9
MORE if required first)
Select 5 CTB/CSO SETUP to enter that menu
Select 0 INTERACTIVE if
it is desired to manually select the beats to measure
Do not select 1 AUTO as
CTB cannot be measured without carrier removal
Select 2 AUTO (PAUSE FOR CARRIER OFF) for a slow measurement with better accuracy
Select 3 SINGLE SWEEP for a speedy measurement with good accuracy
The AUTO TEST LOCATIONS should read:
4 +1.250 MHZ
(OFFSET)
5 +750.000 MHZ
(OFFSET)
6 + 0.000 MHZ
(OFFSET)
7 -750.000 MHZ
(OFFSET)
8 -1.250 MHZ
(OFFSET)
Optionally, the lowest offset may be deleted
if the upper band-edge of the lower adjacent channel creates false CSO
To delete it, Select 8 –1.250 MHZ (OFFSET), Press W=DELETE
Press BSKP as
needed to return to the CATV
MEASUREMENTS menu
Select 7 IN-CHANNEL RESPONSE to (Select 9 MORE if
required first)
Select 5 IN-CHAN RESP SETUP to enter that menu
Select 0 INTERACTIVE for
manual placement of the high/low markers on the headend injected multiburst pulses
Select 1 AUTO for
the recommended automatic placement of the high/low markers on the multiburst
pulses
Press BSKP as
needed to return to the CATV
MEASUREMENTS menu or any “MENUS” key to exit
Setup for these tests is now complete
Test Instructions for the Tektronix® 2714 CATV Analyzer
To Tune to the Channel Desired for Test:
Press channel number(s) desired on KEYPAD
Press W on
KEYPAD
To Test Carrier to Noise:
Press CATV/APPL in
the button grouping labeled “MENUS”
If the analyzer is in a test mode other than
the one desired, Select 9
to leave
If needed, Select 5 CARRIER TO NOISE
to enter that menu (Select 9 MORE if required first)
Select 0 RUN CARRIER/NOISE INTERACTIVE
For unmodulated carrier, on MOVE MARKER TO NOISE
prompt move marker near channel center (+/-
2MHz)
Press W to
continue
For modulated carrier, on MOVE MARKER TO NOISE
prompt first remove carrier, then move marker as
above
Press W to
continue
Record the displayed results
Tune to the next channel desired and repeat
the steps listed above
To Test CTB/CSO:
Tune to the channel desired
Press CATV/APPL in
the button grouping labeled “MENUS”
If the analyzer is in a test mode other than
the one desired, Select 9
to leave
If needed, Select 5 CTB/CSO to enter that menu (Select 9 MORE if required first)
Select 2 RUN CTB/CSO to run the test in the
mode selected during setup
When prompted, turn off the carrier
Press W to continue and follow any
further prompts depending on test mode
The display will show the worst case
Press CATV/APPL
Select 2 DISPLAY RESULTS
All results for both both CTB and CSO will
display
Record the displayed results (only worst case
for each of CSO and CTB is required)
Press W to
continue
Press any “MENUS” key to exit
Tune to the next channel desired and repeat
the steps listed above
To Test Hum and other Low Frequency
Disturbances:
Tune to the channel desired
Press CATV/APPL in
the button grouping labeled “MENUS”
If the analyzer is in a test mode other than
the one desired, Select 9
to leave
If needed, Select 6 HUM/LFD to enter that menu (Select 9 MORE if required first)
Remove modulation (recommended) for a system
Hum/LFD reading
Leave modulation for a reading of all LFD
(source video may influence reading)
Select 0 RUN HUM/LFD
Record the displayed result
This test is only needed on one channel at
each test location
To Test In-Channel Response:
Tune to the channel desired
Press CATV/APPL in
the button grouping labeled “MENUS”
If the analyzer is in a test mode other than
the one desired, Select 9
to leave
If needed, Select 7 IN-CHANNEL RESPONSE
to enter that menu (Select 9 MORE if required first)
Select 0 RUN IN-CHANNEL RESPONSE
Inject the multiburst test signal when
prompted
Press W to
continue
Remove the multiburst test signal when
prompted
Press W to
continue
Record the displayed result
Tune to the next channel desired and repeat
the steps listed above