User's Manual Part 2

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Ignition Systems
All high tension wiring from the ignition coil through to the spark plugs should be
kept as short as practicable, clean, and as close to the engine block as possible.
The cable should be an impregnated neoprene resistive type and the coil must be
either mounted on, or immediately adjacent to, the engine block. The low tension
wire from the coil to the distributor contact breaker points must be as short as
possible, and not included with other wires in a harness or loom. This wire must be
shielded if more than 300mm long. Twin flex or 'figure eight' cable provides a
suitable shield when connected in lieu of the original wire. This method is useful for
shielding other wires suspected of radiating noise. Do not ignore the wire to an
electric tachometer if one is fitted.
Coil to Battery Wiring
A low pass filter such as that supplied in the interference suppression kit or similar
should be fitted at the coil end of this wire. The earth connection of the filter should
be short and well-bonded to the coil body.
Battery Charging System
The charging system circuit, consisting of either generator or alternator and a
regulator may also be split into three parts:-
Alternator / Generator to Battery Wiring
A low pass filter such as that supplied in the interference suppression kit or similar
should be fitted to the main battery lead at the alternator. The filter must be rated
for the maximum current available from the charging system. The earth lug of the
filter should be attached to the alternator body or the engine block.
Alternator to Regulator Control Wire
This wire carries switching pulses that often contribute noise to the receiver.
Suppression using capacitors or filters must not be attempted since damage to the
regulator may result. Separate the wire from all other wiring, keep it as short as
possible and, if longer than about 300mm it should be shielded as described above.
Other Regulator Wires
These are normally adequately suppressed using good low-inductance bypass
capacitors. To be effective, these capacitors must connect to the wires to be
suppressed and to chassis with very short leads. For this reason, the 'pigtail' style
of suppressor capacitor often used with MF broadcast receivers is generally
ineffective at HF.
Other Noise Sources
Electric Motors (Windscreen Wipers, Fans Etc.)
Small electric motors can usually be suppressed with good low inductance bypass
capacitors.