Cable Integrity and Cable Loss Test in GSM

Cable Integrity and Cable Loss Test in GSM Cable Integrity Test

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Cable integrity is checked by measuring VSWR.

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A good known cable is connected from the test transmitter to the wattmeter.

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The cable under test is placed between the wattmeter & 50 Ohms load.

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Forward and reverse power levels are measured and VSWR can be calculated as ,

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Each cable should be checked and any that exhibit greater than 1.2 : 1 VSWR must be replaced.

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Cable integrity check must be performed on all jumpers and antenna feedlines.

Cable Loss

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All cables used for testing must be measured and clearly labelled with insertion loss before they are used.

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These are normal wear items and so it is important to replace any cables that become kinked or frayed or that are worn or damaged connectors.

Step 1 Test

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Connected a cable ‘A’ directly to the wattmeter.

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Terminate the other end of the wattmeter with a 50 ohms resistance.

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Insert 1 Watt element in forward position.

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Adjust to full deflection .

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Record reading ‘A’

Step 2 Test

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Connect cable ‘B’ as shown.

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Turn transmitter on.

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Record reading ‘B’.

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Cable Loss for cable B in dB = 10 log10(B/A)

Transmitter Setup

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If the propagation test is being done for model tuning to produce a generic model for macro cells, then a high point in the particular area has to be selected.

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The transmitter and the transmit antenna will be placed at this point (say the roof of the building ).

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The transmit antenna is connected to the transmitter via a RF cable.

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Check to see that the cable is connected properly and tight.

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Loosely connected or faulty cable can increase the VSWR.

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A test frequency has to selected from the frequency band allocated to the operator. Set the transmitter to this test frequency.