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For a typical dual-band “base” VHF/UHF antenna designed for exterior mounting on a structure or mast you can expect to pay anywhere from several dozen dollars to several hundred, depending on quality, durability, and performance factors such as gain.
This rugged antenna, an omnidirectional collinear, is capable of surviving harsh environments. It's a good choice for repeater installations and can be top, or side mounted to the tower. You can obtain approximately 3 to 10 dB of gain over a dipole, depending on the number of elements you use.
This calculator can be used to design a Quarter Wave Ground Plane antenna, with radials. The radiating element is a quarter wave (λ/4) and the radials are 12% longer. There are usually four radials, three being a minimum, but you could use up to six.
Antennas are most efficient at sending out and capturing radio waves when the antenna's length is matched to specific fractions of the radio wave's length. For marine VHF (frequencies between 156 MHz to 163 MHz), a formula tells us the wavelength is about 1.91 metres.
This page contains construction details on a 2 metre 144MHz VHF Yagi beam antenna, designed for portable use. Since an old 5 element version (v1) of my antenna was shown in the July 2011 edition of RadCom, a few people have contacted me asking for some information on how it was constructed.
This is an introduction to a high gain VHF/UHF vertical collinear antenna program and project that can be an asset to many of you that are looking for more gain in a vertical antenna for base or repeater use. An added bonus is an extremely low angle of radiation! The approximate gain is 9dbd+....not dbi!
The antenna designs presented here are specifically cut to the dimensions necessary f or proper operation in 140 -150 MHz VHF band. Each chapter deals with a particular design and an extra chapter at the last part is added to help the constructor in converting the given antenna dimensions for other frequencies.
