Cable test is first understanding for any RF Engineer here i write how to test cable integrity and Cable loss and testing of Transmitter in gsm.

Cable Integrity Test

Cable Integrity Test

  • Cable integrity is checked by measuring VSWR.
  • A good known cable is connected from the test transmitter to the wattmeter.
  • The cable under test is placed between the wattmeter & 50 Ohms load.
  • Forward and reverse power levels are measured and VSWR can be calculated as ,

  • Each cable should be checked and any that exhibit greater than 1.2 : 1 VSWR must be replaced.
  • Cable integrity check must be performed on all jumpers and antenna feedlines.

Cable Loss

Cable Loss

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

  • Connected a cable ‘A’ directly to the wattmeter.
  • Terminate the other end of the wattmeter with a 50 ohms resistance.
  • Insert 1 Watt element in forward position.
  • Adjust to full deflection .
  • Record reading ‘A’

Step 2 Test

Cable loss test

  • Connect cable ‘B’ as shown.
  • Turn transmitter on.
  • Record reading ‘B’.
  • Cable Loss for cable B in dB = 10 log10(B/A)

Transmitter Setup

  • 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.
  • The transmitter and the transmit antenna will be placed at this point (say the roof of the building ).
  • The transmit antenna is connected to the transmitter via a RF cable.
  • Check to see that the cable is connected properly and tight.
  • Loosely connected or faulty cable can increase the VSWR.
  • A test frequency has to selected from the frequency band allocated to the operator. Set the transmitter to this test frequency.

test transmitter