# What measurements are used to identify a fault in a coax line?

## What measurements are used to identify a fault in a coax line?

Introduction. Distance-to-Fault (DTF) measurements, typically expressed in units of reflection coefficient, return loss, or VSWR as a function of distance, are used to find common faults in coaxial cables and connectors (Table 1).

## How much loss is considered acceptable in the antenna system?

While different systems have different acceptable return loss limits, 15 dB or better is a common system limit for a cable and antenna system.

## What is Logmag?

LOGMAG – For S11 measurements this is the Return Loss and is measured in dB. For passive networks it will always be below negative. For S21 measurements this is the INSERTION LOSS in dB. SWR – The Standing Wave Ratio, often also called Voltage Standing Wave Ratio(VSWR), is often used for measuring antennas.

## What is dB loss in RF?

A 3 dB loss means half the power. For example, a system with 40 watts of input power and a 6 dB insertion loss will only have 10 watts of output power. dB: Decibel, a logarithm (equal to 10 times) ratio of the difference between two values. 0 dBm = 1.0 milliwatt, 10 dBm = 10 milliwatt, 30 dBm = (1 mW x 1,000) = 1 watt.

## How do you test a coaxial RF cable?

Use a multimeter to determine if there is a short or other issue affecting continuity within an RF Cable:

1. Set the meter to the resistance setting with the best resolution.
2. To determine if there is any internal resistance in the meter, cross the black and red probes and note the resistance shown onscreen.

## How can you tell if a transmission line is fault?

How to Find the Fault in Your Transmission Line

1. Figure out the length of your cable without physically measuring the cable.
2. Verify cable performance at the touch of a button.
3. Determine if failures exist in your transmission line and the nature of those failures without visually inspecting the cable.

## Does length of coax affect signal?

Coaxial Cable Length Coaxial cable comes in varying lengths. The shorter and thicker the cable is rated will determine the strength of the signal transmitted. It is important to choose the right cable length and thickness.

## Why return loss should be less than dB?

The return loss measures the reflected wave to the incident wave, that is RL = -20 log(Γ). So, a return loss of -10 dB means that the reflected wave is 10 dB lower than the incident wave. This is approximately equal to a reflection coefficient of 0.3, so 30% of the incident wave is wasted.

## What does a Sitemaster do?

Instrument Description The Site Master S331E/S361E is a handheld cable and antenna analyzer designed to make Return Loss, VSWR, Cable Loss, and Distance-To-Fault (DTF) measurements in the field.

## What is PIM and sweep testing?

Line sweeping measures the signal losses and reflections of the transmission system. PIM testing is a measure of construction quality and poor quality will result in self-interference. PIM testing performance measurements are not relevant unless accompanied by comprehensive line sweep tests.

## What is distance to fault (DTF) measurement?

Distance domain measurements, commonly known as Distance To Fault (DTF), are made over a selectable distance range. The maximum distance range is dependent upon the frequency range. See “Optimizing Frequency Range”, on page 12, for further explanation.

## What is VSWR in cable and antenna measurements?

In cable and antenna measurements signal reflections, which are a result of poor mismatch, are measured. These measurements can be viewed as VSWR or Return Loss with the Site Master. VSWR is the ratio of the maximum to minimun.

## What is the difference between return loss / VSWR and DTF?

If both the return loss of the antenna and system return loss is known, the cable loss can be estimated from this information. Return Loss / VSWR measurement characterizes the performance of the overall system. If either of these is failing, the DTF measurement can be used to troubleshoot the system and locate the exact location of a fault.

## What is the relationship between frequency range and fault resolution?

A wider frequency ranges means better fault resolution and shorter max distance. Similarly, a narrower frequency range leads to wider fault resolution and greater maximum horizontal distance. The only way to improve the fault resolution is to increase the frequency range.