Cable and Antenna Trouble shooting Guide

1 Cable and Antenna Troubleshooting Guide utilizing Anritsu's Handheld Site Master , LMR MasterTM, VNA MasterTM, Cell Master , or BTS Master . Antenna Sweeping Antenna Sweeping (continued) Return loss and VSWR Distance to Fault (DTF) Antenna Isolation Why Sweep Antennas? Maintenance Sweeps Measuring Reflections Comparing Traces For Base Stations Commissioning Sweeps Troubleshooting Sweeps Setting Cable Types Propagation Velocity and Cable loss For Repeaters Why sweep antennas? Poor VSWR/Return Common Faults Limit Lines Frequency Range Setup loss can damage transmitters, reduce the Maintenance sweeps can catch faults early, Poor base station Antenna isolation allows RF. coverage area, and lower data rates.

2 For which will increase network uptime, reduce signals from one base station Antenna to leak instance, a return loss of 10 dB means that dropped calls, and allow consistently higher to another. If the leak is 10% of the total power is not radiated and (if data rates. strong enough, BTS. the transmitter is still running) that the Since every Cable has a different sweep signal quality can be coverage area is 10% smaller than the signature, it can be difficult to judge changes. compromised causing transmitter power settings might imply. But a reference trace, from the commissioning dropped and blocked sweeps, makes it easy to see changes. calls. This sort of problem can affect more Once a problem is spotted, whether from a than just the radios with VSWR alarm or a maintenance sweep, it's poor isolation.

3 Failures time to troubleshoot the problem. mean that the sector is Troubleshooting sweeps are inherently prone to excessive inter- different from maintenance or commissioning modulation distortion, sweeps, since they require a flexible use of which lowers signal the instrument, calibrations, and settings to Return loss , or VSWR if you prefer, can be DTF is a way to locate faults identified by quality, increases accurately locate the fault. FlexCal is a BTS used as a one-number screening tool. Return loss or VSWR measurements. dropped calls, and can Master capability that allows users to change As seen above, the markers for this sweep are Trace comparisons are often used for cause interference with Reduced coverage increases dropped and frequency range without a new calibration, set at the edges of the Antenna 's pass band.

4 Other radio services. diagnostics because small changes in cables blocked calls due to weak signal areas and which is helpful when troubleshooting. The trace between the markers is better than will have large effects on the DTF trace. Base station Antenna isolation limits, when network loading imbalances. dB, (or a VSWR of ) a common limit Common faults Because of this, it is accepted practice to take dealing with cellular systems typically should On the data link side, the increased signal for sweeps with an Antenna at the far end. reference sweeps of each Cable at be lower than the -50 to -60 dBm range, include connector, distortion caused by a low return loss means This trace would typically be accepted as commissioning time for later comparison.

5 Although different situations require different Cable and Antenna that data rates are reduced and capacity good. Reflections are measured using either Changes are often more significant than actual limit numbers. faults. When looking suffers. values. Even so, typical values with a good for faults, it's VSWR or Return loss . These are two different Repeaters with insufficient isolation between Finally, poor Return loss or VSWR can cause important to know ways to measure the same thing. Return loss setup are: the two antennas are prone to oscillations, transmitter shutdown and even damage, that most faults are is a logarithmic scale, and Voltage Standing creating interference that can seriously harm taking out a sector until repaired.

6 Connector related. Wave Ratio (VSWR) is a linear scale. Your Open or Short 0 to 5 dB. communications over a wide area. Keeping Antenna systems in shape means the This includes loose choice can be made by personal preference, Antenna Better than 16 dB. connectors, the unit's limit numbers are given in, or by Repeaters are tested in system as a whole runs better. Uptime is Connectors Better than 25 dB much the same increased, call drops go down, data rates go corroded connectors, and poorly installed company requirements. Here's the conversion connectors. Most formula: Propagation velocity (PV or Vp) directly manner as base up, and both managers and customers are stations; however they happier.

7 Remaining faults are Return loss = 20 log |VSWR +1/VSWR-1| affects distance accuracy. PV must be set Cable related. This either manually or by entering a Cable type. require better isolation Commissioning sweeps provide the basis for VSWR = 1+10 RL/20/1-10-RL/20 numbers. Consult your includes water in the acceptance of the Antenna systems. They Cable , loose weather However the quickest conversion is to just Cable loss also needs to be set accurately, repeater installation also provide a reference trace for use when change the instrument units to the preferred either manually, or by selecting a Cable type. instructions for specific wrap, pinched cables, looking for changes later. For best accuracy, settings.

8 False Cable loss values can mask Return loss guidelines. poorly installed they use a short and a load at the top of the or VSWR problems. ground kits, bullet Limit lines can be The setup for Antenna Antenna run. They may also be done with an holes, and even nails created on the Master The frequency range for DTF sweeps should isolation tests uses the Antenna attached. in the Cable ! A small series sweepers and, be set to stay within the load's bandwidth. If BTS Master, Cell The same data that is used for Return loss or portion of the faults are Antenna related. when, accepted, moved an Antenna is used for the load, any portion of Master, or Site VSWR is also used for the Distance to Fault It is possible to damage GPS antennas by from one instrument to the DTF sweep that goes outside of the pass Master's Two Port (DTF) calculations and display.

9 Users can sweeping. Their active components are not another using a USB band is mostly reflected, reducing the Insertion loss capability. After a two port change between the two displays at will. This intended to take higher power levels so they stick or Compact Flash accuracy of the vertical axis Return loss or calibration (An OSLIT cal), the signal source is reduces the number of traces that must be should be replaced by a load (for Return loss ) Memory. This makes looking for faults VSWR measurements. connected to one Antenna while the sense archived and tracked by half. or a short (for DTF) before measuring the line. straightforward and helps ensure consistency. A wider frequency range improves distance terminal is connected to the other.

10 The Cable loss is also an important commissioning Return loss , with an Antenna on the far end, resolution and lowers the maximum amount of power lost during the transmission Measurement accuracy is critical. That's why check. Excessive Cable loss reduces the should be between 15 to 25 dB. For a line measureable distance. However, if an is the Antenna isolation. there are a variety of calibration routines as radiated power, but also, can mask return loss discussed in other parts of this Guide . with a load on the far end, the value should Antenna is in place at the other end of the Further information on isolation testing can be issues, creating false good readings later. Improper use of the calibration standards, or be between 30 and 40 dB.