Station Set-Up

Question 1

What does EMC stand for and what is it?

Answer 1

ELECTROMAGNETIC COMPATIBILITY (EMC)

EMC is the avoidance of interference from two electronic devices

Question 2

Name four ways your radio could cause interference in other devices/items

Answer 2

Pickup of signals via aerials/aerial cabling (e.g. tv cable running through the house)

Speaker cable pick up

Equipment with poor immunity

Via the mains earth

Question 3

Name a few examples of things that could cause interference with your radio:

Answer 3

Home heating thermostats - these are notoriously “noisy” when the heating turns on and off generating short bursts of noise.
Home lighting - You can get loud clicks when lights are turned on and off, or buzzing from dimmer switches
Engines - A passing motorbike sometimes creates a splatter on radio receivers, and anything with an unscreened motor can do this - such as a lawnmower, generator or a washing machine
Things called Powerlines (or HomePlugs), or VSDL wi-fi routers are also notorious for causing interference to HF at home
Other radios - A passing taxi or emergency services vehicle can often splatter across radio frequencies.

Question 4

Who can help you solve interference issues?

Answer 4

you can get free advice from the RSGB EMC Committee’s website, or of course approach Ofcom (although note a callout fee applies)

Question 5

How can you reduce the effects of interference?

Answer 5

Put ‘chokes’ ‘ferrites’ or filters on the end of cables picking up inteference
Move the transmitting device further away to reduce the field effect
Reduce the transmitter power
Use filters on main power supply leads
Address earth problems
Use a dummy load to test for interference from time to time

Question 6

How does interference when using FM differ to AM/SSB?

Answer 6

FM - causes least interference as amplitude constant (remember: ‘friendly modulation’)
AM/SSB - causes more interference than FM as amplitude changes with signal

Question 7

How can you set up your station to minimise interfernce?

Answer 7

A good RF earth can mimise EMC
You use an RF earth to stop RF leaking into mains
Don’t use mains earth as an RF earth (e.g. radiators, pipes etc.)
A good RF earth is a copper stake in the ground with heavy-gauge wire to connect from the transmitter or AMU to the RF earth.
A balanced antenna creates less EMC than other antenna types

Question 8

what do these things stand for? PSU, VSWR, ATU

Answer 8

PSU = power supply unit
VSWR = voltage standing wave ratio
ATU = antenna tuning unit