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How to Test the VSWR of a Fiberglass CB Whip

Voltage Standing Wave Ratio, or VSWR, is a measurement of the power out of a transmitter versus the power the transmission line and antenna reflect back. The higher the VSWR, sometimes shortened to SWR, the more power loss you system experiences. While a 1:1 ratio is theoretically what you want, it is a physical impossibility. A low meter reading indicates that the impedance from the transmitter output, through the transmission line, and into the antenna is closely matched, and this is what you seek.

Things You'll Need

Antenna mounted in the location it will be used
Coaxial cable transmission line from antenna to transmitter
VSWR (also called a SWR) meter
Short piece of coaxial cable to run from the CB to the VSWR meter (the shorter the better because you will remove this piece after testing the VSWR and that will have an effect on the VSWR)
CB receiver/transmitter
Slotted screwdriver

Instructions

- 1
  Connect the short piece of coaxial cable to the output of the CB receiver/transmitter and connect the other end to the input on the VSWR meter.
- 2
  Connect the output of the VSWR meter to the transmission line coaxial cable running to the antenna.
- 3
  Key the microphone on the CB receiver/transmitter and hold it down.
- 4
  Observe the reading on the VSWR meter. The needle will typically move from left to right as the ratio is increased.
- 5
  Adjust the tuning of the antenna by removing the end cap and adjusting the slotted screw underneath until you have the lowest reading on the meter.

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