1Chelmsford Amateur Radio SocietyM3 Foundation Licence Course

Murray Niman G6JYB Slide Set 7(7) EMC

Chelmsford Amateur Radio Chelmsford Amateur Radio Society Society

M3 Foundation CourseM3 Foundation CourseEMCEMC

2Chelmsford Amateur Radio SocietyM3 Foundation Licence Course

Murray Niman G6JYB Slide Set 7(7) EMC

EMC - Introduction

• EMC - Electro-Magnetic Compatibility

• Consumer Appliances and Radios together in Perfect Harmony!

• EMC has two aspects:-– Avoidance of generating interference.– Immunity of own kit from being interfered with.

• EMC has the potential for causing Neighbour Disputes– Commonly Television Interference - TVI– Sometimes on HiFi, Telephone Lines– Even a few Watts is enough to overpower a TV preamp

• Radio Investigation Service (RIS) handles complaints

3Chelmsford Amateur Radio SocietyM3 Foundation Licence Course

Murray Niman G6JYB Slide Set 7(7) EMC

EMC Precautions

• Suppress problems at their source !

• Modes/Power - SSB causes more problems than FM

• Antenna Position - Space away from TV Antennas, Phone Lines

• Use Lowpass/Band Pass Filters to suppress Harmonics for TVI

• Use Dedicated RF Earths - not Safety Mains Earths

• RF Traps/Ferrite rings on antenna feeders - helps the Source

• Inline Filters, Ferrite Rings may be needed - helps the Victims