Foundation Radio Amateur Licence - BDARS Online Syllabus
Basics of electromagnetic compatibility
Recall that electromagnetic compatibility (EMC) is the avoidance of interference between various pieces of electronic equipment.
Recall that radio transmitters can cause interference to nearby electronic and radio equipment.
Recall that radio receivers can also suffer from interference from local sources. (This is not considered specifically, but most good EMC practice applies to both conditions.)
Recall that interference occurs through local radio transmissions being conveyed to the affected equipment through pick up in house wiring, TV antenna down-leads, telephone wiring etc., and (particularly at v.h.f./u.h.f.) by direct pick-up in the internal circuits of the affected equipment itself.
Station design for EMC.
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 h.f..Recall that, at h.f., (horizontal) dipoles are less likely to be a problem and that end-fed wires present significant EMC problems.
Recall that information on the avoidance of interference by the correct choice and siting of antennas and suitable operating procedures is readily available from several sources.
Recall that the more power a station runs, the more likely it is to cause interference.Recall that some types of transmission are more likely to cause interference to TV, radio and telephones than others.
Recall that s.s.b. is the one of the poorest in this respect. f.m.., c.w. (Morse) and the some of the h.f. data modes (such as PSK31) are much better.
Immunity of radio receiving and other devices and filtering techniques.
Recall that the ability of any piece of electronic or radio equipment to function correctly in the presence of strong r.f. signals is known as "immunity".
Recall that the immunity of most types of equipment can be increased by fitting suitable external chokes and filters in mains or TV antenna leads. Recall that the filters should be fitted as close to the affected device as possible.
Recall that anything fitted to the mains wiring must be properly made for the purpose.Understand that home-made items (other than ferrite rings) are potentially dangerous.
Recall that information about the purchasing, making and fitting of chokes and filters is readily available from several sources.
Recall that the function of the r.f. earth connection in an h.f. amateur station is to provide a path to ground to minimise r.f. currents entering the mains earth system and causing interference to other electronic equipment.
Social issues of Interference.
Recall that EMC problems have the potential for causing neighbour disputes.Understand the need for diplomacy, the sources of advice available and the role of the local office of Ofcom.