
With CB Radio, I Was Told to Feed My with Multiples of a Half-Wavelength—18 feet for CB. Does This Also Apply to Ham Radio?
The 18 feet length is a myth. It might be about half wavelength in free space at CB frequencies but that does not take the velocity factor of the coax into consideration. If an antenna has a perfect match at the feed point, a half wavelength in coax will repeat that match but with velocity factors running between about .66 and .85 for most modern coax, a half wavelength in coax would be between 11.88 and 15.3 feet, not 18 feet.
The proper length of coaxial cable is just long enough to connect the radio and antenna together. There’s no special length needed, no magic measurement so your radio will work better.
Article written by: Mark Haverstock, K8MSH
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