a graphic of the Brats club logo


just a graphic of the foundation course


Link to general information about the FL course

Link to Licence conditions   Link to technical basics   Link to feeders and antennas

Link to Transmitters and Receivers   Link to Propagation   Link to pages on Safety   Link to Electromagnetic Compatibility

Link to Operating practice and proceedure    Link to the general index page at the start of the Foundation licence section

Section 6
Electromagnetic Compatibility


Station design and antenna placement/general principles

6E1 Recall that EMC problems can be minimised by siting antennas as far away from houses as possible, as high as possible, and using balanced antennas at HF.

When you are considering where to place your antenna follow these guide lines :-

Locate the antenna as far away from homes (buildings in general) as possible.

Place the antenna as high as possible, but remember the possibility that in a storm the antenna support might crash to the ground with your aerial !!

Recall that, at HF, horizontal dipoles are less likely to be a problem and that end-fed wires can present significant EMC problems.

Use a balanced antenna at HF - the centre fed dipole (with a balun when fed by coaxial cable) is considered the best antenna as far as EMC is concerned.

Avoid the use of a "long end fed wire" as these have a greater possibility to cause interference than the horizontal dipole. The long end fed wire must be properly matched to the Transmitter by an ATU.

Recall that information on avoiding interference can be obtained from the RSGB's EMC team and experienced local amateur radio club members.

Radiocommunication Agency leaflet RA 179 gives information as to how someone should report interference and RA 234 EMC and the Radio Amateur (Rev. 5, March 2000) are useful sources of more information. You should be aware of these publication.

6E2 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

You need to know that the function of the RF earth connection in an HF 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

Because of developments in the safety of electric mains supply in the home providing an RF earth to your shack is a difficult situation as it may negate the electricity supply company's PME Protective Multiple Earthing.

Thus the PME mains supply and earthing practice can cause problems for radio amateurs.

However you have to know for the written assessment that in your shack there are two basic earths:-

The Electrical Earth

The earth in the mains supply which is connected to your equipment through the main plug.

The RF Earth

The RF earth which is connected to your rig and ATU (if there is such a provision) normally via a wing nut on a bolt to a long ground steak which you will have had to drive into the ground (avoiding electric mains cable, water mains and water waste pipe work that might exist under ground).

You have to know that the only purpose of the RF earth is to provide a direct route to ground for RF currents and thus minimise such current entering the mains earth system and causing interference to other electronic equipment.

With regard to the written assessment, a question about an earthing stake or RF earth the likely answer is - for passing any RF currents to earth.

NOTE: When setting up your station and you intend to use an RF earth check with an NICEIC registered contractor and explain what you propose to do and take the advice given.



Return to topic index


The origin of some of the text on this page is from the RSGB with additions by the web master