Howtosignalprocessing
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.
- How close can VHF antennas be?
- How close can two vertical antennas be?
- How far should antennas be from each other?
- Can two antennas interfere with each other?
How close can VHF antennas be?
How close is too close for a VHF or AIS antenna placed near another antenna or metal object? NMEA recommends 6 feet of vertical and horizontal separation between the VHF and AIS antennas.
How close can two vertical antennas be?
If both antennas on a mast are connected to remote radios, then a minimum of 2-3 feet of vertical separation is typically OK. If one antenna is connected to an access point radio, then it will be transmitting much more, and thus interfere constantly with the other. In such a case, a lot more separation would be needed.
How far should antennas be from each other?
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).
Can two antennas interfere with each other?
Placing two antennas within ~1/2 wavelength of each other will cause them to inductively couple - effectively connecting themselves to each other. This results in detuning both antennas, as well as the high power Tx RF getting routed back down the other antenna, possibly damaging the receiver.
