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Syllabus Sections:-

9c Operation whilst mobile

9c.1 Understand that operating in vehicles and vessels can introduce new hazards (ie. insecure equipment, long/flexible antennas, accidental shorts to earth, lack of attention to driving, RF induction into vehicle control circuits).

Recall the additional safety precautions that should be taken whilst operating mobile and / or maritime mobile (ie secure equipment, cable routing / protection, correct fusing, use of hands free equipment, attention to good radio housekeeping).

When installing all equipment to be used in a vehicle or on a vessel you must ensure that :-

  • it is properly fixed in position so that in the event of an accident it remains in that position

  • all cables used must have their route considered so that they will not interfere with other cables already installed and that it is ensured that the cables cannot be chaffed and cause a short circuit with the possible result of a fire.

  • OLD ADVICE SEE BELOW to reduce the possibility of fire ensure that the correct rated fuse are used in the installation in both the positive and negative lines so that any other fault in the cars electrics does not use the radio equipment's feed as a route for high current.

  • you consider the installation of a main shut of switch that is know by all in the vehicle / vessel.

  • any equipment susceptible to damage by water is kept in water tight compartments - this is particularly important on vessels that operate on tidal water as SALT attacks electronic equipment not only by direct contact but also by spray in the air which also carries salt which causes severe corrosion.

  • when used in a vehicle that hands free operation is installed to reduce accidents due to operating the equipment.

  • any RF generate by the equipment does not interfere with the systems of the vehicle or vessel. Engine management systems and other control circuits are particularly susceptible to interruption to proper operation due to the presence of unwanted RF.

  • after installation that it is checked regularly to ensure that nothing has changed that might cause problems in operation, or fire.

  • antennas are safely installed so that particularly on a vessel they cannot be touched whilst transmissions are taking place. On vehicles long whippy antennas need to be secured whilst the vehicle is moving.

  • Remember that transceivers should be specified for vehicle use and the manufacturer's guidance on RF power limits, antenna placement and DC supplies must be followed. Failure to do so might affect your insurance cover and questions on this point must be directed to your insurance provider.

It is a grey area as to whether a radio amateur can be prosecuted solely for using a hand held microphone whilst they are driving but if they are driving in an unsafe way then prosecution is almost certainly the likely result. It is thus strongly recommended to use a remote switched microphone so that operation is "HANDS FREE"

However reading Rule 149 of the HIGHWAY CODE it says:- "You MUST exercise proper control of your vehicle at all times. You MUST NOT use a hand-held mobile phone, or similar device, when driving except to call 999 or 112 in a genuine emergency when it is unsafe or impractical to stop. Never use a hand-held microphone when driving.

It is thus considered to be illegal to use a hand held mic whilst driving but it may is still open to interpretation.

There is a significant change in the guidance section which affects the Advanced examination and the Advanced course book.

The advice in MPT1362 [the code the RSGB publications are based on] and all copies of Advance up to and including the 2009 reprint was to connect the transceiver directly to the vehicle battery with appropriate fuses in both the positive and negative leads. This does not agree with accepted commercial practise.

The recommendation is now to connect the negative return from the rig to a new point on the body shell, very close to the connection point for the battery strap - but specifically NOT sharing the same bolt as the battery strap because that is a likely failure point.

A one-wire system would be very bad EMC practice. The negative return via the body shell creates a huge pickup loop, parts of which are also carrying other return currents from the car's own electrical systems - an open invitation to RF interference, both from the car and to it.

To minimise the size of any pickup loop, it would be good EMC practice to use the two-wire DC supply with common mode chokes at both ends (there is often one inside the rig) and avoid connecting the rig to the car body in any other way. If an additional connection between the antenna base and the car body is not needed, then don't make one; it it's unavoidable (eg for HF mobile) then make another common mode choke on the coax cable. From where the negative wire terminates on the body shell close to the battery, keep the single red wire taped close to the battery earthing strap on its way up to the positive terminal post; once again you're aiming to minimise the size of any open pickup loop.


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