Quarter Wave Monopole CB Antenna At 24hourCB.com

Antenna Overall Length

106 to 112 Inches (9.84 cm)

Antenna Radiating Element Length
(Tuned on the CB band)

102 to 108 Inches (7.62 cm)

Antenna insulated base

Plexiglas

Antenna Base Anchor

Wood on sheet metal

Antenna Ground Plane Type

4 wires around 6 foot long, depending on the wire size, on the ground on each corner, and anchored down by 4 plastic stakes at the end of the ground plane wires.

Antenna Communication Range
@ 3 Watt RF Power Transmitter

6 to 10 miles (10 to 20 km) on even terrain with less obstruction.

Antenna Gain

3 db gain over a dipole antenna, or 6db over a 1/8 wavelength CB walkie-talkie antenna (52 inches long) at a 11 degree maximum radiation angle above the ground.

Maximum RF Power Rating

2,000 Watts (continuous)

Antenna Bandwidth in that pic

1 MHz (40 CB Channels) @ VSWR < 1.2:1

Antenna Input Impedance in that pic

50 Ohms

Antenna Tunable

Yes

Antenna Base Connector Type

UHF SO-239 Jack

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Quarter wave Monopole Ground Plane Antenna Image

A quarter wave monopole ground plane antenna that is set on the ground is called the Marconi antenna in which that is nothing new, because AM broadcast radio station have been using those type of antennas for around a century, except the AM broadcast radio station antenna's ground plane has 120 wires buried in the ground at least a quarter wavelength in instead of 4 ground plane wires in this pic at 0.155 to 1/6 wavelength for a CB monopole ground plane antenna. Normally, the feed impedance of a quarter wave monopole ground plane with quarter wavelength ground plane wires is 37 ohms. But on that quarter wave CB monopole antenna, 4 wires 5.333 to 6 foot long (0.155 to 1/6 wavelength), depending on the wire size, are used on the ground plane in order to get a 50 ohm impedance match instead of using quarter wavelength ground plane wires. So a monopole ground plane antenna that is tuned on the CB radio frequencies around 27MHz doesn't need too much ground plane wires like on those lower frequency AM broadcast monopole antenna in which they operate on frequencies between 530 to 1700 kHz.

Here is formula for a quarter wave monopole antenna:

Table of Definition
f =	Frequency in MHz (Megahertz)
l =	Quarter wavelength in feet

l = 234 / f

So AM broadcast radio station's quarter wave monopole antenna that is tuned at 530 KHz is 441 feet tall, and a quarter wave monopole antenna that is tuned at 1700 kHz is 137 feet tall. Also radio amateur operators aka HAM use the monopole antennas on the 160 meter band on the frequency range between 1800 to 2000 kHz at around a quarter wavelength at 123 feet tall.

A 5/8 antenna monopole ground plane antenna has around 1db over a quarter wave monopole ground plane antenna or 4 db over a dipole, and it has a lower angle of maximum radiation angle than a quarter wave monopole ground plane antenna. A 5/8 antenna monopole ground plane antenna needs a matching network in order to match the antenna to a 50 ohm transmission line.

All the ground plane element portion of the monopole antenna are at least a quarter wavelength for a 37 ohm match that would require a matching system in order to match the antenna from a 50 ohm system. But all the ground plane elements portion are around 0.69 times the length of a quarter wavelength in order get close to a 50 ohm match.