Jackaroo Diesel EMR.

Submitted: Wednesday, Jul 24, 2002 at 00:00
ThreadID: 1560 Views:3034 Replies:5 FollowUps:1
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To the other owners of the current 3.0 TD Jacks - re the radio interference caused by the injector circuits - I have found a way to get clean reception for the "car" radio (in remote areas - that's where it was really bad), but the long range HF (Scout) is still, being swamped with chatter from the engine bay - any suggestions appreciated (in anticipation, I reckon it is the injectors for sure, because it disappears on throttle up; I have shifted the HF antenna mount away to the spare wheel bracket and even ran the HF radio from a free standing 12 volt battery - you guessed it; still there!).....dp
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Reply By: charl- Wednesday, Jul 24, 2002 at 00:00

Wednesday, Jul 24, 2002 at 00:00
Greetings Darian and
welcome to the best oz touring site around,

Noise generated by motor or electrical accessories on the vehicle may cause objectionable interference to the received signal. The noise enters the receiver either by means of the battery leads or the antenna system. Provided that the radio is connected directly to the battery terminals, and the leads are kept away from the high tension ignition wiring (assuming a petrol engine) noise injected via the battery leads is unlikely to be significant in most cases. Most noise problems result from being generated or minimising it from being radiated by the wiring connected to the noise source.

The techniques involved in noise suppression include re-routing of wiring, screening and the use of filters. It is also necessary to maintain all electrical equipment in good working order as worn brushes, loose connections and the like, will increase the amount of noise generated. Satisfactory suppression cannot be achieved if faults exist in the vehicle to be suppressed. Cracked distributor caps, worm commutators or burnt contacts may not yet be seriously degrading performance of their own system but will generate very high radio frequency noise levels. Before attempting to suppress noise, problems described above should be sought out and rectified.

Before attempting to cure a noise problem, the source (s) of noise must be identified. Ideally, there should be no difference between the background noise in the receiver with the motor and accessories on and that with the motor and accessories off.

If detectable difference does exist, turn off all accessories one by one until a change in noise results. Continue, noting each contributing unit until there is no detectable difference from the "all off" noise level. (For accessories such as alternators, motors, instruments, etc, a wire or drive belt may have to be temporarily removed for this assessment). After identifying each noise source, they can be worked on one at a time until an acceptable level of suppression is achieved.

Some suggestions for suppressing particular noise sources are -

Ignition Systems. - Audible as a popping noise - frequency varies with engine speed

High Tension Wiring.

All high tension wiring for the ignition coil through to the spark plugs should be kept as short as possible, clean, and as close to the engine block as possible. The cable should be impregnated neoprene resistive type and the coil must be mounted on, or immediately adjacent to, the engine block.

Low Tension Wiring

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 300 mm long. Twin flex or figure 8 cable 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 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:-

a. Alternator / Generator to Battery wiring - audible as a whine - frequency dependent on engine speed

A low pass filter should be fitted to the main battery lead at the alternator. This 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 engine block.

b. Alternator to Regulator Control wire ( Generator Field Wire ) - audible as a sizzling noise above engine idle speed.

This wire carries switching pulses that often contribute noise to the receiver. Suppression using capacitors of 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 300 mm it should be shielded as above.

c. 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 used with broadcast receivers are generally ineffective at HF.

Other Noise Sources.

a. Electric Motors (windscreen wipers, fans, etc)

Small electric motors can usually be suppressed with good low inductance bypass capacitors.

b. Engine Instrumentation

Certain types of oil pressure sensors and voltage regulators used in instrument systems contain a vibrating or thermal cyclic contact. The devices can only be suppressed by isolating and screening or wiring in the same way as described for the alternator to the regulator control wire.

c. Mechanical Movement

Moving parts on vehicles such as exhaust pipes, loose body panels, badly fitted roof racks etc, can generate noise. It is essential that all items such as exhaust pipes are securely clamped, and if necessary fit earthing straps to the chassis. The bonnet of the vehicle should have earthing straps fitted back to the body and all body panels should be checked for positive fixing. The majority of roofracks rest into the vehicle gutter with clamps to hold them in place, sometimes there is an earth connection if the paintwork of the gutter is damaged, usually this is not the case and earthing straps should be fitted to ensue that the rack is earthed to the bodywork of the vehicle.

regards charl.
AnswerID: 5115

Reply By: Tim - Thursday, Jul 25, 2002 at 00:00

Thursday, Jul 25, 2002 at 00:00
My T/D Jack radio is fine unless the aerial is right down and the UHF seems unaffected.
AnswerID: 5140

Reply By: Darian - Thursday, Jul 25, 2002 at 00:00

Thursday, Jul 25, 2002 at 00:00
G'day Tim....yes....the UHF is ok - that technology is not affected by the EMR problem - FM on the car radio will be ok too - re your car
radio being fine....have you been in remote areas - long way from the stations ? Interested to know if your are happy when the incoming signal is weak. Thanks dp
AnswerID: 5141

Reply By: Steve - Friday, Jul 26, 2002 at 00:00

Friday, Jul 26, 2002 at 00:00
I. have had no trouble with UHF interference but the AM radio was all static so I took the Jackaroo back to the dealer and they installed a suppressor on the radio under warranty.Now it sounds fine
AnswerID: 5175

Follow Up By: Darian - Tuesday, Jul 30, 2002 at 00:00

Tuesday, Jul 30, 2002 at 00:00
Steve...thanks for the comment....I did the same when the car was new...took it back and they slapped in the filter
(from the radio maker - Eurovox in Melbourne - aboto me in the bush - have you tried your car radio way out back yet ?
WITH the filter in there, using the standard antenna system, I'm stuffed when I get about 3-500km out of the city......dp
FollowupID: 2259

Reply By: Steve - Tuesday, Jul 30, 2002 at 00:00

Tuesday, Jul 30, 2002 at 00:00
Darian I have just recently had the filter installed and have not been bush since but when I do I will let you know how it goes.
AnswerID: 5263

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