6A1 Understand that all electronic equipment is capable of radiating and absorbing radio frequency energy.
Recall that the basic principle of electromagnetic compatibility is that apparatus should be able to function satisfactorily in its electromagnetic environment and without causing undue electromagnetic disturbance to other apparatus in that environment.
It is a fact of life that all electronic equipment is capable of radiating and absorbing radio frequency energy.
The whole idea behind the principle of Electromagnetic Compatibility is that equipment should :-
limit the amount of RF radiation to below a specified level and also
be able to withstand a certain level of RF that tries to enter it.
The levels involved are stated in EMC regulations which thankfully you do not have to learn but must be aware that it is British Standards Institute Immunity Requirements in which the limits are stated.
Modern electronic equipment
What you need to appreciate is that even modern electronic equipment, such as televisions and other domestic electronic equipment, may not be able to withstand strong (or high) local RF transmission.
Computers
The computer you may have in your shack, when switched on will be a constant source of RF noise, even though at very low RF levels, and this can stop you hearing the very low RF signals from the antenna. Thus for serious listening turn off your computer and hear the difference.
6A2 Recall that the immunity of a device can often be improved by screening and filtering power, signal and control leads.
In order to reduce this RF noise pickup it is important to improve
screening of equipment by making sure it is in a metal box or case
which will give what we call a Farady shielding effect, Faraday invented a screened
cage to isolate equipment from outside influences.
Further screening can
be used control leads and DC and AC power cables. More reduction can be
gained by using filters in these leads.
6A3 Understand
that transmitters in domestic environments may give rise
to RF fields stronger than the agreed limits.
Understand that transmitters in domestic environments are
not normal situations and special measures may have to be
taken.
The radio transmitter used for amateur radio is not a "normal" domestic appliance in so far as not every home has one BUT nearly every home has a TV and broadcast radio receiver.
Thus the radio amateur is bringing into an environment a piece of equipment which under normal circumstance would not be there. This places the onerous responsibility on the radio amateur to ensure that the transmitter does not cause undue interference to others nearby.
The transmitter may, well almost certainly, give rise to RF field strengths that are stronger if not much stronger than the specified limits.
It is the amateur radio licence that permits the Radio Amateur to transmit RF power levels above the Directive limits.
However the Amateur Radio Licence also has the requirement that if neighbours equipment does suffer interference then the field strength must be reduced to an acceptable level. Good EMC practice coupled with simple remedies should avoid the need for an enforced reduction in power.
So if you want to keep the likelihood of problem to a minimum then use as low power as possible to ensure communication is achieved (even though you may think your licence permits higher power levels it does but only when it does not cause undue interference).
6A4 Understand that new electronic equipment should meet the British Standards Institute immunity requirements but that existing equipment and poorly installed equipment may not.
With a great deal of new equipment in homes anything made since 1996 must meet the EMC directive on immunity requirements and thus problems associated with lack of EMC immunity is lower. However there is still a great deal of older equipment out there and the regulations are not retrospective so it is still being used and still likely to suffer EMC problems.
Even new equipment badly installed can have problems so it is best to solve your own EMC problems by good housekeeping of the radio installation and using the lowest power which gives good communication.
Bear in mind TV down-leads do have a limited service life, like all equipment and especially if out in the open where it may be subjected to ingress of water (entry of water) and a poor quality lead has very little copper in the braiding and thus has poor screening qualities from your RF signal.
The origin of some of the text on this page is from the RSGB with additions by the web master