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Syllabus Sections:-

Station design and antenna placement / general principles

6E2   45  Understand good RF grounding and bonding techniques.

At intermediate level you learnt about correct earthing i.e. driving earth rods into the ground for both shack and antenna,  this will give you a good earth for most uses and prevent residual RF current floating about either in the feeder (coax as short as possible please) or entering your shack. RF entering the shack could lead to a "hot " radio and possible RF burn, unwanted RF may also cause interference to yours and neighbours electronic equipment.
If we use a vertical aerial as an example, firstly keep it as far away as possible from the house and fit both an " air choke" and and earth rod  and when the coax comes into the shack that too will need to be earthed, this is possible via a common mode choke.
It is also a very good idea to use an AMU or antenna matching unit to reduce RF in the shack, please note the AMU must include an inductive coupler (transformer/balun) in order to be effective.
Please remember do NOT use house radiators,mains earth connections or pipework in the house as an RF earth as this will not work .
Also you need to consider if your electrical installation is PME and precautions to be taken see the page 85 headed DANGER.


The photo above left is PME with the new Earth wire connected to the new earthing block. Note the large white notice this indicates the original installation is PME.
The photo in the middle above shows the new connection to the earth block of the earth cable from the internal consumer unit and not the new yellow notice below the earth block which now makes the installation TT.
The photo on the right above shows the new earth connection to an earth rod and the lead to the meter box in conduit.
This was all carried out under a "Minor Electrical Installation Works Certificate" by a qualified electrician.



Understand the effects of inadequate RF grounding and bonding

Bad grounding and bonding will lead to stray RF throughout the shack and locality,this will lead to various electronic devices i.e televisions, dvd players ,computers,radios,etc all potentially getting some form of spurious rf interference in both your house and others near.More to be written here !!

6E3   45   Recall that balanced antenna systems tend to cause fewer EMC problems than unbalanced antennas.

By using both a balanced aerial that is located in a horizontal plane will cause the least near field interference to house wiring and lessen EMC problems

6E3   45 continued Recall that the feeder (balanced or unbalanced) should fall away from the antenna at right-angles to minimise coupling.

This part of the syllabus is to highlight the fact that the balanced nature of the dipole tends to minimise feeder radiation when fed with balanced feeder but it is important to note that the feeder MUST leave the antenna at right angles to the orientation of the antenna.

Usually the dipole will be supported on two poles or masts one at each end and the feeder will then drop away to the ground.

When using the dipole your aim is to maintain as far as possible the balanced nature of the antenna and its feeder.

This sort of antenna arrangement then tends to cause least EMC problems.

Next   Mobile installations



Syllabus copyright Ofcom


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