Homemade 3 Inch Short
Stubby 27 MHz
CB Antenna For CB Walkie Talkie Units
|Antenna Overall Length||3.875 Inches (9.84 cm)|
|Antenna Radiating Body Length||3 Inches (7.62 cm)|
|Antenna Radiating Element Length||2.125
to 2.625 (5.4 cm to 6.67 cm)
or 1/194 to 1/157 wavelength
|Antenna RF Connector Base||BNC|
|Antenna Plastic Enclosure Type||Polypropylene|
@ 3 Watt RF Power Transmitter
|1.5 to 3.2 miles (2.4 to 5 km) on even terrain with less obstruction, or 1.5 miles @ S9 S-meter signal strength by the CB receiver.|
|Antenna Gain||-13db gain under a 1/8 wavelength walkie-talkie antenna (52 inches long) or (0.05 transmission power factor to a 52 inches long antenna), or -19db gain over a quarter wave ground plane Marconi CB antenna setting on the ground with 4 ground plane wires 6 foot long laying on the ground or (0.0126 transmission power to a quarter wave ground plane Marconi CB antenna).|
|Maximum RF Power Rating||5 Watts (continuous)|
|Antenna Input Impedance||50 Ohms|
300 kHz bandwidth (27 CB Channels) @ VSWR < 3:1
|Antenna SWR Graph Reading:|
The Advantage Of A 3 Inch CB Antenna:
It could be used in trucking yards by yard employees outdoors on the ground, and it is easy to carry around in the trucking yard to communicate with those owner and operator of those commercial trucks that are conducting business with the trucking yard.
The Disadvantage Of A 3 Inch CB Antenna:
It has a very short communication range 3 miles or less. It can not be used while the antenna is near any adjacent objects, and that antenna must be position above that adjacent object in order for optimum performance; or it can not be used indoors inside of the trucking yard office buildings in which those walls may block the radio transmission that would limit the communication range, or it may cause interference when that walkie-talkie unit is operated too close to computers, or telephone voice or data lines, or any other electronic devices unless that walkie-talkie unit is operating on low power mode of 1.5 watt or less at a distant from those electronic devices or telephone and data lines more than 3 feet away.
Other Information About The Antenna
This antenna has an impedance matching L network to convert 50 ohm input to 100 ohm antenna feed point to help improve ground plane system that would require very little ground plane like a hand grasping a walkie talkie unit without direct contact with any metal that is connected to the walkie talkie metal chassis in which that would improve antenna radiating output. So without that matching L network, more ground plane is needed on a very short antenna less than 6 inches in length at the 11 meter band (27 MHz CB band) or 30 MHz or lower frequencies in order to maintain a 50 ohm antenna system in which more ground plane is impractical for CB handheld transceivers.
3 Inch Antenna Diagram: Click Here To View
This 3 inch CB antenna is just an experimental antenna. So the shortest CB antenna on the market is 7.25 inches in overall length around 1/57 wavelength with a communication range around 2.5 to 4 miles from handheld to mobile. The shortest most effective CB antenna is 12 inches (30.5 cm) in radiating element length or around 1/34 wavelength with a communication range around 4 to 6 miles from handheld to mobile.
So using very short length of transmitting antenna with a wavelength less than 1/40 is nothing new, and those radio amateur operators (HAM) have been using those small fraction wavelength antennas for many decades. At the 80 meter HAM band (3.5 to 4.0 MHz), a quarter wavelength is around 60 feet, or a eighth wavelength around 30 feet, or 1/10 wavelength around 24 feet; and that would be physically too impractical for mobile use or handheld use. On any HF band frequencies (3 to 30 MHz), a 9 foot antenna or shorter is more physically practical for mobile use, and a 5 foot antenna or shorter is more physically practical for handheld use. So on the 80 meter HAM band a 9 foot antenna is around 1/27 wavelength, and 5 foot antenna is around 1/48 wavelength. So any antennas shorter than a quarter wavelength on any bands requires a loading coil in order to properly match the antenna impedance to the transmitter.
But on the CB band, 9 foot antenna is a quarter wavelength is physically practical for mobile use with a communication range around 8 to 12 miles from mobile to mobile, and a 5 foot antenna is a 1/7 wavelength is more physically practical for handheld use with a communication range around 6 to 10 miles from handheld to mobile. But those short antennas less than a quarter wavelength has less db gain than a quarter wavelength antenna, and the shorter the antenna more db loss it has, and the shorter the communication range.
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