How to Tune an Antenna

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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

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    • 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.
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    On a CB radio, tune to Channel 1.
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    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.
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    • 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.
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    • 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).
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    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.
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Community Q&A

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  • Question
    Can I use an SWR meter for a digital TV antenna?
    Imhungry Imhungry
    Community Answer
    No, there are digital tuning meters for tuning signals, but the cheapest I have seen is about $200 and most are over $1000. For $40 you can buy a converter box and use the built-in tuning meter for aiming your antenna, but it isn't battery powered and portable.
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  • Question
    How do I find the built in digital antenna on an LG TV?
    Community Answer
    It will be on the back of the TV and will usually be a metal bolt with a white center and hole through, also known as coax. It also may be labeled ANT or Antenna.
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      Tips

      • SWR meters gauge the efficiency of your antenna: in other words, what percentage of the energy devoted to the antenna is actually being used to transmit. Although a well-tuned antenna is simply one in which the SWR readings at the lowest and highest ends of the band are identical, you should try for SWR readings of 1.5 or less for optimal efficiency. If you have especially high SWR readings, try adding a transformer mechanism between the radio and the antenna or add a mode choke to the outside of the coaxial cable to prevent energy seepage.
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      • Always tune your antenna when it is in its natural position as its SWR readings will change as it moves away and toward different structures. If you are using a home-bound antenna, ignore Step 1 and tune the antenna in place.
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      Warnings

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      Things You'll Need

      • Radio
      • Antenna
      • SWR meter
      • Two lengths of coaxial cable


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      References

      1. http://www.hamuniverse.com/testingswr.html
      2. http://www.roadtripamerica.com/Equipment/How-to-Tune-a-C-B-Radio-Antenna.htm
      3. http://www.rightchannelradios.com/pages/cb-antenna-tuning-and-swr-explained-pv-c0-58.html

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