Radio Station Earthing



I start with a simple question. I have a choice of three earths for my radio room.
  1. A copper earth stake at 1.2 ohms 50 meters away attached with 6mm domestic earth cable.
  2. A copper earth stake at 65 ohms 6 meters away direct adjacent the radio room and attached
    with 6mm earth cable.
  3. The house wiring earth which is part of the MENS network and is therefor connected at the
    mains supply distribution box the the electricity generators Neural line.
So which individual earth or combinations of earths do I choose? Each has its advantages and why
not tie them all together to get the best solution?

The turmiol that surrounds us

Electrically speaking we live in a very turmulucious world. It is a bubbling cauldrin of electrical chargers and magnetic flux. There are bubble of activity all around us, but the bubbles are not the steam like boiling waer but magnetic flux and electricl charges. LIke steam they are been continually generated and like steam vapoutise just as quickly. The generators can be a simple as running a plactic comb hair ot starting the two stroke grass mower. In fact the earth itself is amassive generator of charge with it;s iron core swirling around way beneath our feet.

The quiet amoungst the electricla storm

So how do we find a place where the dim of the magnetic strorm is quite. The best we have was theory developed by a guy born in 1791 called Faraday. We call it a "Faraday cage". Michael Faraday was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic induction, diamagnetism and electrolysis. See https://en.wikipedia.org/wiki/Michael_Faraday A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields https://en.wikipedia.org/wiki/Faraday_cage So why not go out and buy a roll of mesh and wrap up the whole radio room and bond it to all the earth points we can find.

A practical solution

One reason is that not all earth are created equal. There is no such thing as a perfect earth. Even a very good earth will introduce transients into the radio room, especially if we have 50 meters of earth cable acting like well posotioned antenna. As we have discussed there is also lots of generators of charge out there, so it there are differing earth potentials currest will be flowing. Electrolies is a battery source. Connect two dissimilar metals is moist soil or wet condition and connect them to the same earth copper wiring and you have a constant battery flowing to hold up a elctrical potential on the earth system. This could be a simple as connecting an earth to a galvanised antenna pole staked to the ground and a copper earth stake nearby. To make matters worse some amateurs water the earth stake, or emerse the earth stake in a PVC tube, that is watered along with the Vegie patch to lower the earth resistance. Electrolicis requres four things: an anode, a cathode, an electrolite, and a circuit. Illinminate any one of these and you are safe to use a "wet earth". However, a word of warning. Termites need water and they will seek out damp, moist ground. In many places in Austarlia termites are very aggressive and can do a lots of damage to building structures without being detected, so if your earth stake is close to the building you choose to regularly watering the earth stake, It might be advisable to consult an insect professional.

The one Good Earth

A good duscussion on ground earths can be found here: Bentinite and Similar Products

A summary of thsi article:

Bentonite is a clay substance used in areas with high soil resistivity. However, conduction in bentonite clay only takes place via the movement of ions. Ionic conduction can only occur in a solution, which means the bentonite clay must be moist to provide the required resistance levels. When bentonite clay loses moisture, its resistivity increases and volume decreases. This shrinkage results in a discontinuity in the contact between the bentonite clay and surrounding soil, which further increases system resistance.

Coke powder is another choice. A predominantly carbon substance, coke powder is highly conductive. However, groundwater can wash it away.

A noncorrosive low-resistance enhancement substance is a conductive cement that you can install wet or dry. The material binds the water into a cement making a permanent, highly conductive mass. Unlike bentonite clay, the cement-like material does not depend on the continuous presence of water. Also, it does not require periodic re-charging or replacement.

One example of such a cement is San Earth:

San Earth

Chemical-type electrodes are another option for difficult grounding situations. These consist of a copper tube filled with salts installed in an augered hole or trench. The electrode is backfilled with a ground enhancement material. The copper tube has holes in it near the top and bottom, and the top of the electrode remains exposed to the atmosphere. Water slowly dissolves the salts, which enter the tube from the top holes exposed to the atmosphere. Highly conductive salt solution leaches into the soil from the holes near the bottom of the tube. Chemical-type electrodes require periodic recharging of the salts.

Conductive Concrete

Conducrete® is a conductive concrete used in the construction of grounding electrodes. WA Lightning Protection Services uses Conducrete due to its ability to conduct electricity much more effectively than regular cement.

WA Lightning Protection Services - Conducrete

-----------

Bentinite and Similar Products

Sodium Bentonite.Calcium Bentonite Bentonite Resources Pty Ltd is located at Ebenezer, near Ipswich, west of Brisbane, in South East Queensland Bentonite Resources Pty Ltd

• Four Types: Magnesium, Potassium, Calcium and
Sodium
• Two main types of bentonite: Calcium and Sodium
• Sodium bentonite has high water absorption properties and will expand many times its size. Also known as “swelling bentonite”.
• Calcium bentonite has much lower absorption properties and generally flakes off. Also known as “nonswelling bentonite”.
• Calcium bentonite is the most common type found in the world.
• Calcium bentonite can be converted into sodium bentonite through sodium activation. (Calcium ions are exchanged for sodium carbonate.)

PDF on Bentonite


Soil Description Average Resistivity (Ω – m)

[Top][Home]

Lightning Arrestors

Lightning Arrestor - Polyphaser Model:IS-B50HU-C0

[Top][Home]

Reference Sites

LIGHTNING PROTECTION for RADIO COMMUNICATION SITES
by Phillip R Tompson BE(Hons) CPEng MIE(Aust) MIEE MIEEE
Technical Director NOVARIS PTY LTD
http://www.novaris.com.au/images/stories/Sales%20Kit/SK09/Radio%20Comms.pdf

[Top][Home]
Glenn Lyons VK4PK
glenn@LyonsComputer.com.au
Ver:gnl020320118 - pre published v0.9