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Haibeck Automotive Technology
Radio Antenna Ground Plane Upgrade
GM issued a service bulletin for an improvement to the radio antenna. It can enhance the quality of FM radio reception. This is applicable for ’90 and ’91 Corvettes. Some customers have been very impressed with the results. The results are dependent on the quality of your local radio signals and the quality of the installation. High quality installations are performed only if the installation is exactly as specified by the GM technical bulletin. The improvement was incorporated into factory production in the ’92 - '96 model years.
The process is to create a ground plane for the antenna. Four wires that are ¼ wavelength long are joined together to form an electrical ground field at radio frequencies. The C4 Corvette has a narrow steel band located under the antenna. It was designed to function as a ground plane, but was found to be too small for optimal performance. Other cars don’t have this difficulty because metal exterior panels provide the ground plane.