A VSWR of less than 1.5:1 is ideal, a VSWR of 2:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although a VSWR as high as 6:1 may still be usable with the right equipment.

What is high VSWR?

It is the ratio of the highest voltage anywhere along the transmission line to the lowest. Since the voltage doesn’t vary in an ideal system, its VSWR is 1.0 (or, as commonly expressed, 1:1). When reflections occur, the voltages vary and VSWR is higher — 1.2 (or 1.2:1), for instance.

What does VSWR 2 1 mean?

Standing wave ratio
For example, the VSWR value 1.2:1 means that an AC voltage, due to standing waves along the transmission line, will have a peak value 1.2 times that of the minimum AC voltage along that line, if the line is at least one half wavelength long. …

What if VSWR is less than 1?

If the VSWR = 1.0, there would be no reflected power and the voltage would have a constant magnitude along the transmission line.

What is VSWR formula?

A ratio of infinity to one occurs when the load is an open circuit. A ratio of 1:1 occurs when the load is perfectly matched to the transmission-line characteristic impedance. VSWR is defined from the standing wave that arises on the transmission line itself by: VSWR = |VMAX|/|VMIN|

What is bad VSWR?

Poor VSWR/Return. Loss can damage transmitters, reduce the coverage area, and lower data rates. For instance, a return loss of 10 dB means that 10% of the total power is not radiated and (if the transmitter is still running) that the coverage area is 10% smaller than the transmitter power settings might imply.

Why is VSWR bad?

Although the term VSWR is normally used, both the voltage and current standing waves can cause issues. This means that a poor match between the feeder and antenna will result in a high SWR which causes the output to be reduced and hence a significant loss in transmitted power.

Can VSWR be negative?

Summary. It is possible to have ρ>1. VSWR calculated from ρ is singular where ρ=1, and will yield negative VSWR where ρ>1.

What does a VSWR of 2 mean?

A VSWR value under 2 is considered suitable for most antenna applications. The antenna can be described as having a “Good Match”. So when someone says that the antenna is poorly matched, very often it means that the VSWR value exceeds 2 for a frequency of interest.

Why is the VSWR negative?

Using the simple formula given below it is possible to convert a given value of VSWR to an equivalent return loss. Being a loss the returned power must be less than the forward power, and hence the return loss has a minus sign – negative figures of decibels represent a loss.

What is the range of values for VSWR?

This is also known as the Standing Wave Ratio (SWR). The range of values for VSWR is from 1 to ∞ . A VSWR value under 2 is considered suitable for most antenna applications. The antenna can be described as having a “Good Match”.

What is the VSWR of a standing wave?

The ratio of the maximum adjacent voltage of standing wave to the minimum adjacent voltage of standing wave is the voltage standing wave ratio (VSWR). If the VSWR is over large, the communication distance will be shortened and the reflected power will return the transmitter.

How is VSWR measured on a transmission line?

VSWR is a definition that measures the standing wave condition on a transmission line. It is defined as the ratio of the voltage at the maximum point to the minimum point on a lossless transmission line. Although the current on the transmission line also satisfies the same relationship, measuring voltage is always easier than measuring current.

What should the VSWR of an antenna be?

If the impedance matching of the antenna matches the impedance of the transmitter and the feeder, the measured VSWR should be 1:1 or 1. When the impedance cannot be completely matched, the VSWR may be 2:1 or even more than 5:1. Why do we usually say that the standing wave ratio will affect the antenna feed system? The main factors are as follows.