P51
The Importance of Being Earthed
Radio waves can be dangerous
The Importance of Earthing
There are two different types of earthing that form a part of an antenna system. There is a Safety Earth and there is an RF Earth. Each is intended to perform a different role and need to be discussed separately
RF Earthing
Radio Frequency earthing addresses unwanted RF currents that may be present when you transmit.
An effective RF earth will:
- Minimise unwanted currents in your shack
- Reduce unwanted interference
- Improve the efficiency and effectiveness of your antenna
- Reduce likelihood of receiving RF shocks
- Reduce unwanted interference to your radio, computer and electrical appliances
RF earthing seeks to discharge elements of interference from your transmissions to earth. The radio itself can be more stable if the chassis of the transmitter is correctly grounded.
Where coax cables run up a mast to the antenna, the braid can act as an antenna for local noise which ultimately shows up as extra noise combined with received signals. Grounding of the coax shield close to the base of the mast can significantly reduce this noise source.
Sometimes an RF Earth can be applied away from a radio to help reduce noise. For example Solar panels may be electrically earthed and safe, but poorly earthed for RF, allowing inverters to radiate noise through solar panels. An RF earth applied to solar panels can help.
A common procedure is to have a section of copper pipe running along behind an operator area, that is securely grounded, that various radios and accessories can be connected to via individual earth straps.
Good articles and testimonials can be found at the QRM Guru website via this link:
Safety Earth
This connection is normally installed and maintained by qualified electricians. It is the earth connection which protects people and equipment from the possibility of electric shock. Generally only one good earth stake is established per household and this can be a long way away from Amateur radio equipment.
More detail about this can be found at these tile links:
This item discusses the need for Lightning protection.
https://thisisamateurradio.com/p30-lightning-protection-methods/
ACMA Syllabus Extract
According to the ACMA Foundation Syllabus, the required knowledge on this topic is:
7.11 RF Earthing
Recall that the function of the RF earth connection in an amateur station is to provide a path to ground to minimise RF currents entering the mains earth system and causing interference to other electronic equipment.
Identify, from supplied diagrams, the symbol representing an earth connection.
9.4 Electrical Earthing
Recall why most mains-operated equipment should have a safety earth connection.
This Is Amateur Radio 