How to Tune an Antenna

Music98

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posted on 13 years ago — updated on 1 second ago

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When first setting up a radio or moving a radio to a new, permanent location, its antenna needs to be tuned. Learning how to tune an antenna entails lengthening or shortening the antenna so that, for the radio's specific frequency, it is working as efficiently as possible. In order to tune an antenna, a radio needs to be hooked up to an SWR (standing wave ratio) meter using coaxial cables. This guide will teach you how to test an antenna's efficiency using an SWR meter, and how to tune your antenna accordingly.

Steps

Go to an open area free from buildings, trees, radio towers, or other structures.

Put your radio and antenna in the positions in which you will use them. For a CB radio, put the radio in the car and the antenna on the body of the vehicle. For a portable radio, move away from any vehicle and stand alone with the radio.

Remove any connections between the antenna and the radio.

Attach the radio to the transmitter socket on the SWR meter using a coaxial cable.

Attach the antenna to the antenna socket on the SWR meter using a coaxial cable.

Set the radio to minimum power and to FM or CW mode.

Tune to the lowest band available. On a CB radio, tune to Channel 1.

Transmit from the radio or, on a CB radio, press the talk button.

Observe and record the SWR reading. It should be in the form of a ratio, e.g. 2.2:1. Repeat Steps 6-8 for the highest band available, or, on a CB radio, Channel 40.

Determine from the difference between the SWR readings whether your antenna is too short or too long. If the SWR reading on the lowest band, or Channel 1, is greater, your antenna is too short. If the SWR reading on the highest band, or Channel 40, is greater, your antenna is too long.

Adjust your antenna accordingly, and very slightly. For most antennas, this means manually lengthening or shortening the antenna. For a wire antenna, clip off a bit of the end to shorten it (if you have a wire antenna that is already too short, you will need to get a new antenna).

Repeat Steps 7-10, tweaking your antenna gradually until the SWR readings on the lowest and highest bands, or Channel 1 and Channel 40, are identical.