How to Calibrate a Radio Shack SWR Meterby Pamela Gardapee
The Radio Shack standing wave ratio meter (SWR) is used to check the standing wave of a CB radio or a ham radio. The meter measures the SWR during transmission. If the standing wave is too high, the transmission on the CB or shortwave radio is inefficient. The acceptable standing wave reading should be 1.0 to 1.5 for excellent transmission, 1.5 to 2.0 for good transmission and 2.0 to 3.0 for acceptable transmission. Anything above 3.0 is inefficient and must be corrected in order to use the radio without damaging the unit.
Turn off the radio to be used. Disconnect the CB or shortwave radio antenna from the radio.
Wind the RG-58U coaxial cable onto the antenna jack on the radio and connect the other end to “Transmitter” on the back of the SWR meter. Connect the CB or shortwave radio antenna coaxial cable to the “Antenna” on the back of the SWR meter.
Turn on the radio and set the function switch on the meter to “CAL.” Select a communication channel on the CB or shortwave radio. On the CB or shortwave radio, turn the dial to a channel 1 down or up from a channel that you normally talk on. For instance, if you normally talk on channel 19 on the CB, select channel 18 or 20 so as not to interfere with other users' conversations.
Press the microphone transmit button in as you would if you were going to talk, but do not talk. Turn the “Calibration” knob on the SWR meter so that the needle points at “CAL,” which is all the way to the right on the meter.
Remove your finger from the microphone transmit button. Move the function switch from “CAL” on the meter to “SWR.”
Press the microphone transmit button one more time. Look at the meter. The needle on the meter will move into a range. If the radio that you are using has less than 20 watts, use the lower numbers and if the radio has over 20 watts of power, use the upper numbers.
Read the standing wave ratio number. If the number is too high, adjust the antenna and repeat steps 3 through 6.