What is the collinear antenna?
The collinear antenna, also called the "collinear" or "collinear antenna field", is a set of dipole antennas aligned along their length, making it one long line. Each element of dipole antennas is 1/2 wavelength. Properly aligned and phase, collinear fields can provide 3 dB or greater increase in signal strength. Increasing the signal strength of 3 dB is approximately equal to the doubling of the signal force. This increase in the signal strength is perpendicular to the length of the field, so the fields are usually mounted vertically to increase the signal strength in the horizontal plane. The four-green collinear antenna consists of two separate antennas, each of which has two elements and each element of 1/2 wavelength long and mounted vertically, so all the elements are in line. They are connected using a coaxial cable cut to 1/2 wavelength of a long, calculated using a cable speed factor. It is this coaxial cable that keeps the antenna elements in the phase.
coaxial cable has what is called the "speed factor", which is based on the type of insulation used. The speed factor should be marked on the outside of the cable. The length of the necessary coaxial cable is found by accepting the length of 1/2 of the wavelength and multiplying it by a speed factor. For example, if the cable speed factor is 0.66 or 66 percent, multiply 1/2 of a wavelength of 0.66.
In the range of 144 MHz, the popular variations used by amateur radio operators are called the collinear antenna "Stocked-J" or "J-Pole". In this antenna, the coaxial cable braid is connected to an element of 1/2 of the wavelength pointing down and folded into the “U” figure, each long section is about 1/4 of the wavelength. The central conductor is connected to the vertical 1/2 of the wavelement element, another 1/2 wavelength at the top, with the two connected element of the 1/2 wavelength, moving in the shape of "U" and mounted horizontally. This element is used to insulate two vertical elements.
at frequencies above 300 MHz You can use the lengths of the coaxial cable to produce a collinear antenna using the cable speed factor to determine the length and alternation of the connection of each part. The center connector of section 1 connects to the braid of section 2; Section 1 is connected to the center conductor of section 2, etc. Phase between sections is determined by the distance between each section.