What is a SWR Meter

The SWR meter or VSWR (voltage standing wave ratio) meter measures the standing wave ratio in a transmission line. This is an item of radio equipment used to check the quality of the match between the antenna and the transmission line.

As defined in Wikipedia Article SWR meter "The SWR meter or VSWR (voltage standing wave ratio) meter measures the standing wave ratio in a transmission line. The meter can be used to indicate the degree of mismatch between a transmission line and its load (usually a radio antenna), or evaluate the effectiveness of impedance matching efforts."

Directional SWR Meter
A directional SWR meter measures the magnitude of the forward & reflected waves by sensing each one individually, with directional couplers. A calculation can then be performed to arrive at the SWR.

Limitations
Note that an SWR meter does not measure the actual impedance of a load (i.e., the resistance and reactance), but only the mismatch ratio. To measure the actual impedance, an antenna analyzer or other similar RF measuring device is required. Note also that for accurate readings, the SWR meter must be matched to the line impedance, usually 50 or 75 ohms. To accommodate multiple impedances, some SWR meters have switches on the rear, to select the resistance appropriate for the sense lines.

An SWR meter should be connected to the line as close as possible to the antenna: All practical transmission lines have a certain amount of loss, which causes the reflected wave to be attenuated as it travels back along the line. Thus, the SWR is highest closest to the load, and only improves as the distance from the load increases.

When not actually measuring SWR, it is best to remove the more usual types of passive SWR meter from the line. This is because the internal diodes of such meters can generate harmonics when transmitting, and intermodulation products when receiving. Because active SWR meters do not usually suffer from this effect, they can normally be left in without causing such problems.

References:

• Wikipedia - SWR Meter
• ARRL Antenna Handbook: The ARRL Antenna Book (21st ed.), The American Radio Relay League, Inc., 2007, ISBN 0-87259-987-6

Purchase Commercial DSWR Meter:

Contact Us if you require RES-100 DSWR Meter with details and specifications below:

Digital SWR Meter, Model RES-100 is an improved version of earlier SWR Meters with analogue meter having multiple scales for reading signal level & SWR values. It is simpler to operate and gives accurate results.

RES-100 gives direct digital display of SWR readings in the range of 1.00 to 19.9, thus avoiding the need of expanded SWR scale and greatly simplifying the operation.

Gain control of 0-60db is provided through a 7-position band switch and an accurately calibrated gain control of 0-10db through a variable gain control potentiometer.

Designed primarily for use in making standing wave measurements in conjunction with suitable detector and slotted line or wave-guide section, it is a high gain tuned amplifier operating at a fixed frequency of 1 KHz.  It is calibrated to indicate SWR directly or signal level in db when used with square law detector devices like crystal diodes.

RES-100 operates in two modes – Normal & Audio. In Normal mode, it is used for measurement of db & SWR. In Audio mode, the detected voice signal from crystal detector is amplified and can be heard through a head-phone / speaker.

Output of SWR meter can also be recorded through BNC connector provided at the back of the panel.

Model   operates on 220VAC / 50Hz mains supply. Choose option 01 for operation of instrument on 110VAC / 60Hz