Here is the rule: The horizontal distance between antennas should be greater than 1/4 of its wavelength (absolute minimum separation), but it should not be located at the exact multiples of its wavelength (maybe avoid the first 3-4 multiples).
How do you measure isolation between two antennas?
Isolation between a GPS and WIFI antenna that are near each other will be on the order of 20-30 dB, with higher values being preferred. The method of measuring isolation is typically done by connecting both antennas to a Vector Network Analyzer, and measuring S12 (the transmission coefficient).
Does a repeater need two antennas?
High-power repeaters usually require two antennas, one for receiving and one for transmitting. To make installation easier, some repeaters have what’s called a built-in or add-on duplexer that allows the unit to transmit and receive on the same antenna at the same time.
How far apart should UHF antennas be?
The easy answer is that you should maintain a minimum mounting distance of at least 1/4 wavelength apart for the lowest frequency antenna within the same horizontal plane.
Can two antennas interfere with each other?
Antennas that operate on different frequencies should be placed so that they will not interfere with each other. Simply placing the antennas further apart, with consideration for their radiation patterns, will create some separation, which will help.
How do two way repeaters work?
A repeater enables two-way radios to achieve better coverage, better penetration, and longer range than is possible without a repeater. How does it work? A repeater receives the radio signal on one frequency and simultaneously transmits the same signal on another frequency.
What is the recommended separation distance for UHF antennas?
As general rule, separation distances are chosen as a multiple of wave lengths. UHF separation distance is shown in the following table, based on a wavelength of 0.75m at 400MHz. If the antenna cannot be installed on the top, it is recommended to place antennas at least 1.5 m from the tower for a omni array and 0.75m for a directional array. 1.5 m
What is the DBJ-UHF base repeater antenna?
The DBJ-UHF base repeater antenna is an omni-directional gain antenna for UHF without Radials. It was designed and patented by Dr. Ed Fong (WB6IQN). The antenna was originally developed under a grant from AC Daugherty Inc. for a MESH network. Dr. Ed Fong, or one of his graduate students, personally makes every antenna.
How far apart should antennas be mounted?
The easy answer is that you should maintain a minimum mounting distance of at least 1/4 wavelength apart for the lowest frequency antenna within the same horizontal plane. For VHF antennas, that translates to roughly 19 inches. This is the rule we use when installing omni antennas on a the trunk of a vehicle.
What is the Friis formula for antenna isolation?
The Friis formula can be used to calculate isolation for any relative position and orientation of two antennas. If the antennas are located and oriented such that they are in the sidelobe region of each other, the peak gain level in the sidelobe regions can be used. Isolation = 22 + 20 log(r/ λ) – (Gt,SL + Gr,SL)
