FM Systems SDI MASTER Manuel utilisateur

SDI-1

SDI MASTER

INSTRUCTION BOOK

IB-6374-01

SDI MASTER

TABLE OF CONTENTS

1.0 SHIPPING INSPECTION.

1.1 DESCRIPTION.

2.0 DIGITAL TELEVISION DATA SIGNALS THIS METER WILL MEASURE.

3.0 HOW TO MEASURE SIGNAL STRENGTH ON (SD) TELEVISION SIGNALS.

4.0 MEASURE THE FREQUENCY RESPONSE EQUALIZATION ON SD TV SIGNALS.

5.0 HOW TO MEASURE SIGNAL STRENGTH OF HD TELEVISION SIGNALS.

6.0 MEASURE THE FREQUENCY RESPONSE EQUALIZATION ON HD TV SIGNALS.

7.0 HOW TO MEASURE CABLE TERMINATION IMPEDANCE.

8.0 HOW TO MEASURE CABLE TERMINATION RETURN LOSS.

9.0 HOW TO MEASURE 60 Hz COMMON-MODE INTERFERENCE.

9.1 CARE AND MAINTENANCE.

9.2 BATTERIES.

9.3 OPTIONAL CHARGER.

9.4 AUXILIARY EQUIPMENT.

1.0 SHIPPING INSPECTION

Remove the unit from the shipping container and inspect for shipping damage. If any damage is

found contact the shipping carrier for further instructions. The SDI-1 is shipped fully tested and ready for

use. You should have the SDI-1 meter with a 9V battery in the battery compartment, (Note the battery will

not be attached to the snap-on battery clip for shipping reasons). Open the slide-off lid then snap the

battery connector onto the battery and replace the cover. The meter is now ready to use.

1.1 DESCRIPTION

The SDI-1 MASTER is a hand-held, battery operated, digital meter that measures the signal

strength and necessary cable equalization required by SD and HD Television Signals when transmitting

these digital signals over coaxial cable or other transmission facilities that may cause level or high

frequency loss and consequent data loss.

In addition to measuring signal strength and cable equalization requirements, this meter can also

measure inaccuracy of CABLE TERMINATIONS and the resultant RETURN LOSS that can introduce

data error. Inaccurate cable termination will result in some part of the data signal being reflected back

down the cable. If the sending end termination is the same as the characteristic impedance of the coaxial

cable, the entire reflected energy will be absorbed at the sending end and no data errors will result.

However, if the sending end does not accurately match the characteristic impedance of the cable, some of

the data will be re-reflected back toward the data receiver, mangling the pulses by mixing with the

subsequently arriving pulses. Data errors will be reduced by insuring that all cables are accurately

terminated to avoid the return loss condition that is a major cause of data errors.

The SDI-1 meter will also measure 60 Hz. common mode interference (also known as Ground

Loop interference) introduced by unbalances in AC Power Distribution that can also introduce data errors

when the amplitude of the interfering 60 Hertz signal exceeds the linearity limitations of the data receiver.

Since Unbalanced power loads are endemic to all business locations and the Data Signal uses the same

grounds as the Power Industry, these power unbalances are directly injected into the Data Channel. Since

the amplitude of this common mode interference will vary with time, it must be checked by regular

measurement of the cable facilities to insure that excess common mode interference is not present. It is

possible for AC Power to create as much as several volts of potential between different grounds that are

only a few feet apart, particularly if supplied by the opposing phase from the power source, while the Data

Signal in only 0.8 Volts in amplitude at the best, and may well be much lower after traversing a long

cable. It does not require much Common Mode interference to compress a data signal out of existence.

Furthermore, this type of interference comes and goes with time, and can be very hard to establish what is

causing the problem without some method for measuring this trouble condition.

2.0 DIGITAL TELEVISION DATA SIGNALS THIS METER WILL MEASURE.

This meter is designed to measure Standard Definition (SDTV) and High Definition (HDTV)

digital television signals, such as the 270 Megabit signals used to transmit SDTV using the 525i/59.4 and

625/50 formats, and the 1.485 Gigabit signal used to transmit HDTV using the 1080p/24, 1080p23.98,

1080PsF/24, 1080PsF/23.98, 720p/60, 720p/59.94, 720p/50, 720p/30, 720p/29.97, 720p/25, 720p/24,

720p/23.98 formats.

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3.0 HOW TO MEASURE SIGNAL STRENGTH ON (SD) TELEVISION SIGNALS.

Disconnect the coaxial cable from the receiving data terminal. Connect the coaxial cable to be

measured to the input coaxial connector marked (INPUT) on the SDI MASTER. Connecting the SDI

MASTER to a distribution amplifier that in turn is connected to the cable is OK, IF the distribution

amplifier does not correct frequency response or amplify the signal in any way (as some distribution

amplifiers do). In order to use a D.A., it must simply repeat the exact signal received from the cable in

order to obtain meaningful results from this measurement. If a unity gain D.A. is not available, then the

cable must be removed from the receiving terminal and connected to the SDI MASTER directly.

Rotate the selector switch on the SDI-1 meter to "SD LEVEL" (on the left-hand side of the

switch). Depress and hold down the button at the bottom of the meter to observe the meter reading. The

reading is in Volts peak to peak. Since the decimal point is in front of the number, the actual number reads

in milliVolts, peak to peak. When the reading is complete, release the button to conserve battery power.

A reading of 0.800 volts peak-to-peak indicates that you are measuring the direct nominal output

of a digital video source. As the SDTV signal traverses the coaxial cable, this voltage will be reduced with

distance traveled. A cable that is commonly used by the Television Broadcast Industry is the Belden

1694A Precision Video Cable. When this cable is used, the signal strength can be expected to drop by a

constant percentage for each 100 meters of cable. Since the maximum data rate for SDTV is 270

megabits, the highest fundamental frequency of interest is 135 MHz. This corresponds to a 100 meter loss

of 6.89 dB, which is a reduction of the signal voltage to .4524 times the original 0.800 Volts peak to peak,

or a voltage of 361.9 milliVolts peak-to-peak. Since this is the voltage at the highest frequency of the

SDTV signal, and not at all frequencies, the actual signal will not be reduced that much. An indication of

the expected signal strength at various lengths of cable can be found in the table below.

SIGNAL STRENGTH OF SDTV SIGNALS

FEET OF CABLE METERS OF CABLE MILLIVOLTS

0 0 800

164 50 566

328 100 413

492 150 307

656 200 236

820 250 188

984 300 147

1,148 350 127

1,312 400 107

1,476 450 99

The signal strength of a data generator is supposed to be 800 milliVolts at the output, but it may

vary as much as +/- 10% from this value, so expect that the meter reading may vary at least that much

when estimating cable length using the signal strength that is measured.

SDI-1isb Page 2 of 8

4.0 MEASURE THE FREQUENCY RESPONSE EQUALIZATION ON SD TV SIGNALS.

Coaxial cable losses are greatest at the highest frequencies and lower at low frequencies and all

frequencies must arrive at the data receiving location at nearly the same amplitude, therefore the signal

must be "equalized" prior to delivery to the data terminal if the amplitude discrepancy between the highest

and lowest frequencies are too great. The SDI MASTER measures this differential signal amplitude with

frequency and reads out this differential amplitude between the high and low frequency amplitudes in dB.

This reading is the total amount of equalization that must be provided by in-line equalizers to reduce data

errors to a minimum. Failure to provide these equalizers will increase the number of data errors and

program outages.

To make this measurement, disconnect the receiving end of the coaxial cable from the data

receiver and connect the cable to the "INPUT" coaxial connector of the SDI MASTER. Rotate the

selector switch to SD EQUALIZQATION (on the left side of the switch). Depress and hold down the

power button for the duration of the measurement. The read-out will be in decibels. This displays the total

amount of equalization that must be applied between the cable and the data receiver to obtain optimum

data transmission and reduce data errors.

Occasionally a data source may be encountered that is transmitting at a higher level than 0.800

Volts. In this case, an equalization measurement made near the data source may indicate a negative

deciBell equalization reading. This does not constitute an error, it merely indicates that a level exists in

excess of 0.800 Volts at that point in the cable. Farther away, down the cable, the reading will become

positive again to indicate the amount of equalization to be provided.

5.0 HOW TO MEASURE SIGNAL STRENGTH OF HD TELEVISION SIGNALS

Disconnect the coaxial cable from the receiving data terminal. Connect the coaxial cable to be

measured to the "INPUT" coaxial connecter on the SDI MASTER. Rotate the selector switch on the SDI

MASTER to HD LEVEL (on the right hand side of the switch), and depress and hold down the button on

the bottom of the meter to observe the meter reading. The reading is in Volts peak-to-peak. Since the

decimal point is in front of the number, the actual number reads in milliVolts peak-to-peak. When the

reading is complete, release the button to conserve battery power.

A reading of 0.800 volts peak-to-peak indicates you are measuring the direct nominal output of a

digital video source. As the HDTV signal traverses the coaxial cable, this voltage will be reduced with

distance traveled. A cable that is commonly used by the Television Broadcast Industry is the Belden

1694A Precision Video Cable. When this cable is used, the signal strength of the highest frequency of

interest in HDTV can be expected to drop 84.9 % percent for each 100 Meters of cable. Since signal

strength is the sum of the amplitude of all of the harmonics, the actual signal strength to be expected at

various lengths of cable is shown in the table below.

SIGNAL STRENGTH OF HDTV SIGNALS

FEET OF CABLE METERS OF CABLE MILLIVOLTS

0 0 800

164 50 408

328 100 249

492 150 167

656 200 123

820 250 99

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The signal strength of the data generators is supposed to be 800 milliVolts at the output, but it may

vary as much as +/- 10% from this value, so expect that the meter reading may vary at least that much

when estimating the cable length using the signal strength that is measured.