Pretty sure I know thee right opinion, but want to hear your views. Hopefully I can describe the application clearly to minimize confusion.
First what I am NOT TALKING about is a tower or Antenna Mast located on or next to a building. I know what the Bonding requirements are in that application as I have made a career out of that on the commercial side. Ham Radio operators have a lot of misconceptions about bonding and what they call a RF Ground is outside the scope of NEC but there is a Gray Line. So here goes.
Ham Radio Operators operating on the lower frequencies of 14 Mhz and below operate be on what is called a 1/4 wave vertical antenna, and the antenna is the Tower itself and can be anywhere from 33-feet to 200 feet in height depending on the frequency of operation. Lower the frequency, taller the tower. The Towers will be located some distance from the building roughly as far as the tower is tall.
The Tower itself is the radiator and physically isolated from the Tower Base mounted on Ceramic Isolators. In other words it is electrically Floating. With this type of installation, requires an RF Ground to operate against. The RF Ground is constructed or copper wire radials, and the radials are as long as the tower is high. Thus why the tower is located away form the building. There will be as few as 8 radials up to 180 radials. The radials may be bare or insulated, laying on top of dirt or trenched in a few inches below the surface. A fairly typical installation uses #14 AWG THHN.
OK the transmitter is located in the building some distance away, and there is a COAX that runs from the Transmitter out to the Tower. Center Conductor connected to the Tower, and the shield connected to the Radials. Hopefully I painted that picture in your minds correctly.
So now the question. Is there any requirement from the NEC to bond the RF Ground Radials to the Building Ground Electrode System?
I say NO there is not, but physically it is bonded unintentionally via the Coax Shield.
However I would say best practice is to run a 4 AWG Bonding conductor from the building GES to where the Radial join together at the tower so as to shunt as much lightning current off the Coax to earth as possible.
Now here is what is really scary and most Hams have been told to do. They sink a Ground Rod or two where the Coax enters and fail to bond them to the GES. They are under the impression th eRF Ground must be isolated from the AC Service ground. They bond the ADU to their isolated rods thinking this protects them which is false and extremely dangerous. They fail to realize their Antenna Coax Shield makes the bond through their Radio > Power Supply > AC Power Cord inviting lightning in and travel through their house wiring. I digress, lets stick with the one question on RF Ground Radials.
FWIW Commercial AM Radio Broadcasters use this method.
THX
First what I am NOT TALKING about is a tower or Antenna Mast located on or next to a building. I know what the Bonding requirements are in that application as I have made a career out of that on the commercial side. Ham Radio operators have a lot of misconceptions about bonding and what they call a RF Ground is outside the scope of NEC but there is a Gray Line. So here goes.
Ham Radio Operators operating on the lower frequencies of 14 Mhz and below operate be on what is called a 1/4 wave vertical antenna, and the antenna is the Tower itself and can be anywhere from 33-feet to 200 feet in height depending on the frequency of operation. Lower the frequency, taller the tower. The Towers will be located some distance from the building roughly as far as the tower is tall.
The Tower itself is the radiator and physically isolated from the Tower Base mounted on Ceramic Isolators. In other words it is electrically Floating. With this type of installation, requires an RF Ground to operate against. The RF Ground is constructed or copper wire radials, and the radials are as long as the tower is high. Thus why the tower is located away form the building. There will be as few as 8 radials up to 180 radials. The radials may be bare or insulated, laying on top of dirt or trenched in a few inches below the surface. A fairly typical installation uses #14 AWG THHN.
OK the transmitter is located in the building some distance away, and there is a COAX that runs from the Transmitter out to the Tower. Center Conductor connected to the Tower, and the shield connected to the Radials. Hopefully I painted that picture in your minds correctly.
So now the question. Is there any requirement from the NEC to bond the RF Ground Radials to the Building Ground Electrode System?
I say NO there is not, but physically it is bonded unintentionally via the Coax Shield.
However I would say best practice is to run a 4 AWG Bonding conductor from the building GES to where the Radial join together at the tower so as to shunt as much lightning current off the Coax to earth as possible.
Now here is what is really scary and most Hams have been told to do. They sink a Ground Rod or two where the Coax enters and fail to bond them to the GES. They are under the impression th eRF Ground must be isolated from the AC Service ground. They bond the ADU to their isolated rods thinking this protects them which is false and extremely dangerous. They fail to realize their Antenna Coax Shield makes the bond through their Radio > Power Supply > AC Power Cord inviting lightning in and travel through their house wiring. I digress, lets stick with the one question on RF Ground Radials.
FWIW Commercial AM Radio Broadcasters use this method.
THX
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