The re-calibration mode is only available for the Models ASX-16B, ASX-16C and ASX-16C/D. Do not attempt any type of calibration until you have read these calibration instructions, and have made sure that you have connected and configured the necessary equipment supported by the software. The software that may be used is the Matrix CATV Equipment Control Software. Any version should work, but the latest version is available at our web site: www.matrixtest.com.
The Base Level and Frequency Trim
calibration functions are selected from the "Re-Calibrate"
menu that can be accessed from the main control screen of the CATV Control Software.
In the Model ASX-16 series generators, a Base Level adjustment is used to compensate for variations in module output levels.
There are 2 base leveling functions
that may be selected from the Re-Calibrate menu.
One is fully automatic, “Fully
Automatic Base Level Cal”, which sets the attenuators, finds the lowest level
module, and sets all modules to a calculated base level nominally 0.35 dB below the lowest
level. The other is entered by selecting
“Auto/Manual Base Level Cal” where
the base levels for selected modules can be manually adjusted.
Display all carriers on a spectrum analyzer in CW with levels set to step 480. If the ripple is > 1 dB then you may need to perform a base calibration to achieve optimum leveling performance. If the ripple is > 6 dB then the automated calibration will not work until the ripple is brought to within 6 dB. This may require identifying the lowest and highest modules causing the ripple and consulting Matrix personnel.
Base levels have been set at the
factory and should rarely need to be re-calibrated. If the RAM containing these stored
values becomes corrupted, you can re-load the base levels previously saved to a file using
the LOAD function on the File Access
panel at the lower right of the base leveling screens.
(See Load a File Procedure) If this brings the base levels to satisfactory
levels, i.e. < 1dB ripple then it is unnecessary to proceed with the base calibration
and this procedure may be skipped.
Automatic Base Level adjustments can
only be performed if your system is equipped with an IEEE-488-compatible spectrum analyzer
or RF power meter. Base Levels can be adjusted manually if a GPIB equipped device is not
available, but this is a much slower process.
· Connect RF output from the generator
directly to the power-measuring device.
· Connect GPIB cable from powering
measuring device to PC controller or other GPIB connection.
Make sure the GPIB cable is also connected to the Matrix generator.
· Select System Setup menu on the
main screen of the CATV Control Software. Select
the Power Measurement Device tab on the System Setup screen, select the
model spectrum analyzer or power meter to be used, and select the Spectrum Analyzer or
Power Meter option. Check that the IEEE 488
Address field for the corresponding device on the form corresponds to the address setting
in the measuring device. If they do not, then
modify the address so that they are the same.
The CATV Equipment Control Program will
prevent you from modifying the Base Levels unless you have properly configured the
microcontroller board. To prevent accidental
corruption of the generator’s factory calibrated base levels, most of the newer
generators have included a base lockout switch that overrides the base flag
clearing command unless the proper code is set (Switches S3 & S4 on the
microcontroller board should be set (with generator power off) such that S3 = 7,
and S4 = 5). If the base flag cannot be cleared, a message will display informing you
to make sure the switches are set to the proper enable code. After calibration is complete, these switches
should be reset to any settings other than 7 and 5 to protect the
calibration from being corrupted or erased accidentally.
After having met the connection and configuration requirements above:
1. From the main screen of the CATV Equipment Control program select the Re-Calibrate menu. Then select Fully Automatic Base Level.
2. Click on the START button to activate the automatic base leveling function.
The level of each channel is checked on the first pass through all of the modules at their maximum level step. The weakest module number and level are displayed in the Low module and Low Level dBmV boxes on the form. Another pass is made through all of the modules setting the base levels to the module level of the weakest channel.
3. When the automatic process is completed, all of the modules are turned on and displayed on the spectrum analyzer, if the measuring device is an analyzer, but the carriers are not turned on when using a power meter. Save the new base level configuration to the disk drive. (See To Save a File procedure)
The Base Levels should be set so that when all modules are on level step 480 the output from the generator is flat in amplitude, from the lowest-frequency carrier, to the highest to within about +/- 0.5dB. To manually adjust the Base Level of a module, do the following:
1. From the main screen of the CATV Equipment Control program select the Re-Calibrate menu. Then select Auto/Manual Base Level Cal
2. Click on the Manual Base Leveling button, the bottom, left-hand side of the screen becomes enabled.
3. Select the module to be adjusted in the Select Module scroll box. If the module you want is not displayed, use the list's up and down arrows to scroll the displayed data, then click on your selection. The current Base Level setting for this module will appear in the small window to the right of the Base Level slide bar.
4. Slide the Base Level slide bar up or down to set the new Base Level. Each count, from 0 to 300 will cause a small change: roughly 0.025 dB per step, near the upper end of the adjustment range. Although the number will change in the window as you move the control up and down, the change in Base Level will not yet be sent to the generator.
5. To send the change to the generator, click on the OK button. To abort this adjustment, click on the Exit button, which will re-enable the buttons in the upper right-hand side of the screen.
6. Repeat the above steps for each module to be adjusted.
7. To leave the Manual Base Leveling mode, click on the Exit button.
8. When you are done, save the new Base Level configuration to the disk drive. (See Save a File Procedure)
The carrier frequencies of the Model ASX-16 series generators (models ASX-16B, ASX-16C, ASX-16C/D) can be fine-tuned to bring them within a specified tolerance. This tolerance is determined by the data in the system configuration file and can also be a randomized offset within a specified limit.
Frequency Trimming can be accomplished automatically or manually. Both require the use of a frequency counter. For automatic trimming, your system must have an IEEE-488-controllable frequency counter.
If the Frequency Trim values are scrambled, because the memory chip of the generator microcontroller board has been corrupted, you could load a previously saved calibration file, if available, from the disk drive before proceeding with any Frequency Trim calibration. (See Load a File Procedure). Loading this file from the disk drive will set the trim settings close to their original values. However, it is recommended that a new frequency trim be performed because the old settings may no longer be valid due to changes over time.
Automatic Frequency Trim adjustments can only be performed if your system is equipped with an IEEE-488-compatible frequency counter or spectrum analyzer supported by the CATV Control Software. A frequency counter is preferable because of its greater accuracy and resolution. Frequency Trimming can be accomplished manually if a GPIB equipped device is unavailable, but this is a much slower process.
· Connect RF output from the generator
directly to the frequency-measuring device. (Note
that ASX-16 series generators equipped with an internal frequency counter are internally
wired and switched and do not require external connection).
If the HP 53181A frequency counter is being used, the software reads
frequencies below 100 MHZ from input #1 and frequencies above 100 MHZ from input channel
#2. A resistive splitter is recommended
to connect the output of the ASX generator to input channels 1 and 2 on the frequency
counter when running the automatic frequency trim.
· Connect GPIB cable from power measuring
device to the PC controller or other GPIB connection on the bus. (For externally connected frequency counters)
· Select System Setup menu on the
main screen. Select the Frequency Counter
tab on the Setup screen that is displayed. Select
the model of the frequency-measuring device from the pull down list box to the right of
the label Group. Check that the number
in the IEEE 488 address field on the form corresponds to the GPIB address setting
of the measurement device. Specify the Frequency
Tolerance to calibrate the generator to in parts per million (PPM). The default is 3 PPM and it is not recommended to
use any tighter tolerances. For the ASX-16C/D
only, the tolerance to use for frequency randomization may be entered in KHz. This is set by default to +/- 5KHz.
The Automatic Frequency Trim can either set the modules to a random offset, or to a user specified frequency tolerance value from the system configuration file to determine how close to the video carrier frequencies to adjust the modules. The randomization of the module frequencies minimizes or eliminates problems of beat cancellations when making distortion measurements with coherent carriers. The random offset method is recommended by Matrix when the generator is to be used with a spectrum analyzer for measuring composite distortion.
1. Before starting the frequency
calibration, set all modules to the Low state from the main screen of the CATV
Control Program to protect the equipment.
2. Set the RF attenuator to 10 dB or less. Note that some frequency counters need a
reasonably strong signal to work properly. If
you need more RF level then set the attenuator lower, perhaps between 0 – 5 dB.
3. Select the Re-Calibrate choice
from the main CATV Equipment control menu.
4. Select “Frequency Trim Calibration”.
5. When the Frequency Trim panel is displayed on the screen, the Random On check box is set to Off by default. To implement random offsets of between +/- 10 PPM up to 5KHz (for ASX-16B and ASX-16C) relative to the designated module frequencies, click the Random On box to set it on. For model ASX-16C/D generators the software will generate random offsets up to the limit specified in the ASX-16C/D Frequency Randomization field.
To set frequencies to the designated carrier frequencies within the tolerance specified in the system configuration uncheck the Random On box.
In the automatic frequency trim mode, the frequency read from the frequency-measuring device is displayed on the computer monitor screen.
6. Select “Automatic Frequency Trim”. The program will try to adjust the frequency within the value entered into the frequency tolerance on the System Setup screen, or to a randomized offset from the specified module frequency if Random On is checked. The program will then continue automatically adjusting every module to the target frequency.
If any channels cannot be adjusted to the specified frequency tolerance, the program will temporarily display a message in the status box and then go on to the next channel. At the completion of the calibration a summary of the modules that could not be set to the target frequency will be listed. When randomization is selected, this message may sometimes occur but the frequency adjustments usually will have been made close enough to the target frequency. (The tolerance used for how close to the calculated randomized target frequency to adjust the module is 0.4 PPM.)
7. When the automatic process is completed, any channels that could not be set to the target frequency within the specified tolerance will be displayed (up to the first 25). Save the new Frequency Trim data to the disk drive. (See To Save a File Procedure). Other useful information is captured in files, such as the target random frequencies selected, the measured frequencies, and their offsets from the video carrier frequencies. (See Capturing Frequency Data to a File for more information)
To manually adjust the Frequency Trim of an ASX-16 series generator (models ASX-16B, ASX-16C, ASX-16C/D) module, use the following procedure:
1. Select the Re-Calibrate choice from the main CATV Equipment control menu.
2. Select “Frequency Trim Calibration”.
3. Click on the appropriate module in the Select Module scroll box. If the module you want is not displayed, use the list's up and down arrows to scroll the displayed module number and frequency, then click on the module to be adjusted. The current Frequency Trim setting for this module will appear in the small window to the right of the Freq. Trim slide bar. The slide bar's position will indicate the relative amount of adjustment range this channel has left, either up to 4095 or down to 0. Settings near the middle of the range (around 2048) will more-often-than-not bring the output frequency into the correct range.
4. Slide the Freq. Trim slide bar up or down to set the new Trim value. Each count, from 0 to 4095 will have an almost negligible effect, but large movements will be easily observed on a good frequency counter. Although the number will change in the window as you move the control up and down, the change in Frequency Trim will not be immediately sent to the generator.
5. To send the change to the generator, click on the OK button. To abort this adjustment, click on the Exit button, which will re-enable the Auto and Manual Frequency Trim buttons.
6. Repeat the above steps for each module you want to adjust.
7. To leave the Manual Freq. Trim mode, click on the Exit button.
8. When you are done, save the new Frequency Trim data to the disk drive. (See Save a File Procedure)
Each time a frequency trim is saved, 2 files will be created. A file called FRQTn.FRQ and one called FRQTn.FRP where n is a sequential number, automatically assigned by the program. This number begins with 0, and corresponds to the ordinal number in the list of files in the File Access list on the Frequency trim screen. The FRQTn.FRQ file contains the calibration D/A control steps.
The file FRQTn.FRP contains the measured and calculated randomized target frequencies (if Random On option is selected), and the difference between the actual frequency and the designated carrier center frequency in KHz. This file may be printed, or loaded into a spreadsheet for analysis.
If the Skip Trim checkbox option is selected, then the program will not adjust the frequencies, but will only record the frequencies in order to enable capturing data to measure frequency drift over time.
The particular screen displayed determines what kind of data the computer will access. For example, the System Setup screen will automatically access (and will only access) system configuration files. The Base Calibration screen will save the calibration data and the Frequency Trim screen will save frequency trim data. This process is handled automatically for you.
Fortunately, all disk access is handled the same way. The following file maintenance operations work the same for all screen and data types.
1) Click on the Load button. A message will appear in the horizontal box: "Press Arrow for Files."
2) Click on the small arrow button (which is to the right of the message). One or more file names will be displayed.
3) Click on the name of the file you want to load. The name will be moved to the message box.
4) To actually load the specified file (which will over-write the data for the current operating conditions), click on the OK button. To abort the operation (and to preserve the current operating conditions), click on the Cancel button.
1) Click on the Save button. A message will appear in the horizontal box: "Press Arrow for Files."
2) Click on the small arrow button (which is to the right of the message). One or more file names will be displayed.
3) If you want to save to a new file, type the name of the file in the message window. The name can be any length, as long as it fits within the window. You may use spaces and punctuation. Descriptive names make it easier to identify the data, later.
If you want to over-write an existing file, click on the name of the file you want to replace with the new data. The name you click on will be moved to the message box.
4) To activate the saving of the current data to the file you specified, click on the OK button. To abort the operation, click on the Cancel button.
To
Delete a File (to get rid of an Outdated File):
1) Click on the Delete button. A message will appear in the horizontal box: "Press Arrow for Files."
2) Click on the small arrow button (which is to the right of the message). One or more file names will be displayed.
3) Click on the name of the file you want to delete. The name will be moved to the message box.
4) To actually delete the specified file (which will make it impossible to recover the file or its data in the future), click on the OK button. To abort the operation, click on the Cancel button.