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1X08 - Tektronix DMA120 Digital Modulation Analyzer

Tektronix DMA120 Digital Modulation Analyzer

The DMA120 Series provides the intelligence cable TV technicians need to efficiently install and maintain HFC distribution plant using 64 or 256QAM transmission

The DMA120 provides analysis of ITU-T-J.83, Annex B 64 and 256QAM

Includes Carrying Case & Accessories As Listed

DMA 120 DMA-120

Tektronix DMA120 CATV Meter DMA-120 CATV Meter Models On Sale Warranty Calibration Backed by The Best Service and Lowest Prices in the Industry.

BC# 20602

Regular Price:$495.00 / Each
Sale Price:$247.50 / Each

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Condition Refurbished / Calibrated
Warranty 90 Day Exchange
  • Tektronix DMA120 Digital Modulation Analyzer (BC# 20602)
  • Ethernet Cable
  • Coax Cable
  • AC Adapter/Charger
  • Power Cord
  • User Manual On CD-ROM
  • Carrying Case (G)
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 Tektronix DMA120 Digital Modulation Analyzer

Affordable, portable, ready for cable system technicians: digital channel 64 and 256QAM transmission performance verification measurements
The DMA120 Series Digital Modulation Analyzers provide answers to nagging questions about how to test and verify performance of your digital plant. Quantification of digital transmission performance ? at any point in your system ? will greatly enhance technical management and decision making. The DMA120 provides analysis of ITU-T-J.83, Annex B 64 and 256QAM and the DMA121 verifies 64 and 256QAM formatted per DVB-C.

The DMA120 Series provides the intelligence cable TV technicians need to efficiently install and maintain HFC distribution plant using 64 or 256QAM transmission. Measurement results provide a clear picture of system performance, minimizing the need to re-visit an installation site or make additional service calls. The DMA120 Series field tools are housed in a rugged, weather resistant package and are powered by an easy-to-change NiMh battery.

Qualify System Performance
The built-in digital demodulator makes possible in-service measurements of:
  • Modulation Error Ratio (MER)
  • Error Vector Magnitude (EVM)
  • Estimated Noise Margin
  • BER before Reed-Solomon (R-S) decoder
  • Estimated BER after R-S decoder with system availability statistics

Modulation Error Ratio (MER):
ETSI ETR290 indicates that MER is the best overall ?figure of merit? measurement to determine QAM signal quality. Although bit error rate (BER) has been widely addressed as an important digital transmission ?figure of merit? measurement, MER provides a much earlier indication of transmission impairments. MER indicates the ratio of average total signal power in the ideal constellation to average error power in the constellation as received by the DMA120 Series. The measurement includes error power due to any impairment. If the only impairment in the test channel spectrum is noise, MER is equal to signal-to-noise. Technicians will feel familiarity with MER because results are expressed in dB, similar to analog transmission carrier-to-noise or signal-to-noise measurements. The DMA120 Series measurement screen (see Figure 1) shows MER vs. time, providing trend information.

Error Vector Magnitude (EVM):
EVM is an alternative ?figure of merit? measurement. It has been a performance measurement for digital communication systems in the past and provides a means of system comparability for some engineers. The same distortion elements are measured as in MER. However, the calculation of error is different and is expressed as a percentage (%) of the maximum voltage in the constellation (at sampling times) as received by the DMA120 Series.

Estimated Noise Margin:
The legacy of rf broadband system maintenance has been based on measurements in the frequency domain. Technicians are conditioned to thinking of system ?headroom? in terms of dB carrier-to-noise or dBc for CSO, CTB, or cross modulation. Estimated Noise Margin indicates the ?headroom? for digital channels and results are reported in dB, similar to legacy analog measurements. Essentially, simulated gaussian noise is added to the input signal until a critical pre-FEC BER of 10?4 is measured. The added, simulated noise equals the Estimated Noise Margin which answers the question, ?how many dB until subscribers are receiving impaired digital services??

Bit Error Rate (BER) before Reed-Solomon (R-S) decoding:
BER is an important measurement to document system performance. The typical system operating goal is to achieve a BER of 10?9. Service impairment will typically be observed at bit error rates greater than 10?4. The BER measurement is the average ratio of bit errors to total bits received in a specified time period. The DMA120 Series BER measurement may be set for any period from 1 to 60 minutes. Results from successive periods can be compared to show a 24-period trend.

Estimated BER after R-S decoding:
BER after R-S decoding represents the service level that the cable system is providing to the subscriber?s TV receiver or computer. The R-S decoder is typically able to correct errors up to an input BER of approximately 10?4. Beyond this value, uncorrected errors pass through the decoder ? this is the value reported by Estimated BER (see Figure 2). System availability statistics are also reported by the DMA120 Series, including:
  • Errored seconds (number of seconds that include an errored block)
  • Severely errored seconds (one-second periods with greater than specified number of errored blocks)
  • Severely disturbed periods (duration of sync loss)
  • System unavailability time (time period containing at least 10 consecutive severely errored seconds)
System availability statistics are very useful for tracking intermittent impairments that may not be observable based on MER or average BER measurements.

Maintain and Troubleshoot Your Digital Video Plant
When performance quality measurements indicate transmission problems, the DMA120 Series can provide assistance to find out what?s wrong. Additional measurements and display modes that can help the technician include:
  • Channel Average Power (Signal Level)
  • Adjacent Channel Levels
  • Spectrum Display Mode
  • Constellation Display Mode with zoom capability
  • Adaptive Equalizer Display Mode
Digital Channel Average Power:
RF signal level measurement is made by integrating all the channel power through a channel bandwidth IF filter. A user-settable offset is available to accommodate probe loss. The Signal Level measurement screen plots signal levels vs. time, providing a convenient display from which to make gain or attenuation adjustments or judge other variables that can impact signal level.

Adjacent Channel Levels:
Potential interference to adjacent channels can be verified using this measurement. The Adjacent Channel Levels display compares the test channel average power to the average power in each of the two higher and two lower adjacent channels. The measurement results screen includes a bar graph comparing the test channel and adjacent channels power. This measurement may be used to check flatness across five channels or verify spectral purity of a QAM modulator.

Spectrum Display Mode:
The channel or system spectrum can be viewed in this mode ? channel symmetry and flatness, and relative signal levels can be visually confirmed (see Figure 3).

Constellation Display Mode:
Digital modulation quality can be visually estimated by viewing the constellation of the transmitted signal (see Figure 4). Distribution impairments can be identified including noise and coherent interferers or modulator impairments such as I/Q imbalance or quadrature error. The DMA120 Series also includes two zoom modes ? a constellation quadrant view and a single constellation box can be selected to closely examine the distribution of symbol landings. Decision boundaries are displayed along with adjacent boxes to make it easy to see the symbol landing patterns (see Figure 5).

Adaptive Equalizer Display Mode:
This display indicates linear impairments such as poor frequency response and reflections. Tap values show how hard the equalizer is working to compensate for impairments. The display includes a bar graph which compares the values of the different taps against a DVB template. Bars approaching or exceeding the template value indicate that there is noticeable system impairment detected at the test point.

New Measurement Technology That?s Easy-to-Use
Using the DMA120 Series is easy. Most measurement functions are no more than two menus deep. Navigation through menus is straight forward and there?s a MENU key on the front panel that instantly gets the user to the instrument?s Main Menu screen. Universal set up parameters are part of a Set Up screen. Measurement specific set up parameters are part of the individual measurement screens. Digital transmission is new to most cable TV system technicians and so are measurements to verify performance. Technicians may not understand exactly how these measurements function or how to interpret measurement results. However, measurements are still required to continue system installation and maintenance activities. The DMA120 Series helps technicians to continue working by providing measurement pass/fail indicators. The system engineer or chief technician can determine the measurement-result threshold values. This enables the technician to continue working if measurements are passing or follow an Engineering directive if failures are encountered. Pass/fail indicators are available for: MER, RF Signal Level, Adjacent Channel Level, Channel Power-to-Noise, Severely Errored Seconds (BER mode). Status indicators also help clarify measurement conditions: the DMA120 Series notes if it?s locking to the incoming QAM signal and also if it?s locking to the R-S decoder output. The actual received symbol rate is also reported.

Operating Convenience
The DMA120 Series uses a moisture? and dust-proof keypad. It uses a high-resolution LCD display with backlight. Contrast controls are conveniently located on the front panel. The DMA120 Series includes many capabilities designed to simplify the job of digital plant installation and maintenance. Ancillary enhancements include:
  • Print screen: Any measurement or display mode screen can be directly printed via RS-232 interface
  • Up to 30 constellations or 100 other measurement results can be stored in internal memory with realtime clock/date stamp, measurement site name, operator name, and ambient temperature
  • PC Card (PCMCIA) input for 2 and 20 Megabyte memory cards to store additional measurement results and/or system channel tables
  • User-changeable, NiMH battery to extend the operating day; battery capacity indicator; user-selectable automatic power down
  • 64 and 256QAM Analysis
  • In-service Digital Channel Performance Verification Measurements at an Affordable Price
  • Measurements Compliant with DVB (ETSI) Standard ETR290
  • Troubleshooting Aided by Constellation, Spectrum, and Equalization Display Modes
  • Most Measurements Require Only Two Keystrokes
  • Pass/fail Indication Reduces Training Requirements for Technicians New to Digital Signal Measurements
  • PC Card (PCMCIA) Slot for Easy Memory Expansion
  • Small and Light Weight
  • Easy-change Battery

Frequency Range (channel center frequency) 54 to 860 MHz
Resolution Bandwidths (typical) 135 kHz, 6 MHz
Input Impedance 75 ?, nominal
Maximum Input RF Power: 120 dBµV (60 dBmV)
AC Volts: 90 V peak
Distortion-free Dynamic Range >40 dB
Sensitivity <20 dBµV (?40 dBmV)
Displayed Level (average power of 64QAM signal at 6.875 Msymb/s): Minimum: 40 dBµV (?20 dBmV).
Maximum: 100 dBµV (40 dBmV).
Attenuation Steps: 5 dB, typical
Attenuation Range: 35 dB, typical
Vertical Scale: 10 dB/div, 10 to 90 dBµV, ?50 to 30 dBmV, ?100 to ?20 dBm
Span Settings: 2 to 824 MHz (fixed to 135 kHz RBW)
Flatness: ±1 dB
Sizes: 64QAM, 256QAM
Evaluation: Full constellation, quadrant, single point (box)
Adaptive Equalizer
Number of Taps: 8 feed-forward; 8 feed-back
Scale: +10 to ?40 dBc
Mask: DVB
Signal Level
Channel Bandwidth: 6 MHz
Level (channel average power): Minimum: 40 dBµV/?20 dBmV.
Maximum: 100 dBµV/40 dBmV.
Accuracy: 64QAM: ±1.5 dB, referenced to 25°C.
256QAM: ±1.8 dB, referenced to 25°C
Reference Units (selectable): dBµV, dBmV, dBm, dBpW
Pass/Fail Indication: User-adjustable threshold
Channel Power-to-Noise
Channel Bandwidth: 6 MHz
Maximum Ratio: 40 dB
Accuracy: ±2.1 dB
Pass/Fail Indication: User-adjustable threshold
In-service Measurement: Noise measurement frequency out of channel
Adjacent Channel Level
Difference Amplitude Range: +10 to ?25 dB
Accuracy: ±2.1 dB referenced to 25°C
Display Vertical Scale: 40 to 100 dBµV, ?20 to 40 dBmV, ?65 to ?5 dBm, 25 to 85 dBpW.
Pass/Fail Indication: User-adjustable threshold
Modulation Error Ratio (MER)
Range: 64QAM: 22 to 35 dB.
256QAM: 28 to 35 dB.
Accuracy: ±1.5 dB at 65 dBµV/5 dBmV, referenced to 25°C
Pass/Fail Indication: User-adjustable threshold.
Error Vector Magnitude (EVM)
Range: 64QAM: 1.2 to 4.1%.
256QAM: 1.1 to 1.9%
Accuracy: ±0.4% over 1.2 to 2.0% range; ±0.8% over 2.1 to 4.1% range at 65 dBµV/5 dBmV.
Average Bit Error Rate (BER), Before R-S Decoding
Range: 64QAM: 10?4 to 10?9.
256QAM: 10?4 to 10?8.
User-selectable Time Period: 1 to 60 minutes
Number of Periods Comparable: 24.
Estimated Average Bit Error Rate (BER), After R-S decoding
User-selectable Time Period: 1 to 60 minutes
Number Periods Comparable: 24
System Availability Statistics
User-selectable Time Period: 1 to 60 minutes
Errored Seconds. Severely Errored Seconds: Pass/Fail indication: User-settable threshold
Estimated Noise Margin
Range: 64QAM ? 1 to 12 dB, 256QAM ? 2 to 7 dB
Accuracy: ±1.5 dB at 65 dBµV/5 dBmV.
Symbol Rate
Range: 5.057 to 5.360 Msymb/s
Operating: ?5 to +40°C.
Operating: Up to 4,600 m (15,000 ft.)
Non-operating: Up to 15,000 m (50,000 ft.)
Qualified Per The Following Standards U.S.A./FCC: CFR 47, Part 15, Subpart B, Class A.
Australian EMC Framework: AS/NZS 2064.1/2.
EU (EMC Directive 89/336EEC):
EN 55011 Class A.
IEC 1000-4-2 (ESD immunity).
IEC 801-3 (RF field immunity).
IEC 1000-4-4 (EFT/burst immunity)
DC Input Range 12 V, 2 A
Battery Run Time >2.5 hours, typical
Battery Charge Time (instrument off) 4 hours, typical.
Height 32 cm (12.5 in)
Width 17 cm (6.75 in)
Depth 6 cm (2.25 in)
Weight Net 2.1 kg (4.6 lb)

For full Tektronix DMA120 product specifications, please click here: Tektronix DMA120
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