Figure 12.83. Interference suppressor installed on a Bosch generator
In order to get rid of extraneous unwanted noise, there is no need to incur large expenses and spend a lot of work, as some people think. With a little common sense and patience, and following the instructions below, you can almost completely eliminate the effects of interference.
The first reason is the generator. The noise it produces in the receiver resembles the operation of an electric mixer, and this noise increases with increasing speed (if you want proof of this, you can remove the drive belt and see what happens). The remedy for this is quite simple: connect a capacitance of 1.0 µF to 3.0 µF between ground and large (B +) generator contact. The last note is very important, because if you connect it to a small contact, then you have the opportunity to ruin the generator forever.
The second most common cause of electrical interference is the ignition system. Here you need to connect a capacitance of 1.0 µF between ground and contact "SW" or "+" on the reel. This will help stop the sounds "tick-tick-tick", heard from the speaker. Next come the candles themselves. High voltage wires already have an interference suppression system, so it is not recommended to do anything else with them. Do not insert suppression caps or trim wires to install suppression into the circuit.
At this stage it is recommended to check that the radio is well grounded and that the antenna is also well grounded and its plug is properly inserted into place and the radio is properly tuned (see previous Section). Also, make sure that the litania wire is the shortest possible length and is not dangling all over the car. It's a good idea to check that the correct fuse is being used. For most receivers this should be a 1 - 2 Amp fuse.
Now most of the causes of interference have been eliminated. If the problem still exists, check out the reasons that cause inertia in general, which can help you figure out what exactly is bothering you specifically in your case.
A radio receiver receives electromagnetic waves from the air; Some of these waves are sent by radio stations and other transmitters, and some, unwanted ones, are sent by the car itself. These homegrown signals are produced by third-party electrical discharges occurring around the vehicle. Typically, the sources of such signals are electric motors; those. windshield wiper motor, washer motor, power window, heater fan or antenna motor. Other sources of interference may include turn signals and instruments. The turn signals are usually not suppressed. In recent years, receiver manufacturers have included a choke in the power circuit in addition to the fuse. If your installation does not have one, you can insert it (see Figure 12.84).
Figure 12.84. Choke in the receiver circuit
All of the above components can be purchased from auto stores. For a transistor receiver, a 2 Ampere choke would be adequate. If you have an electric clock installed, its effect can be suppressed by connecting a 0.5 µF capacitor as shown for the motor in Figure 12.85.
Figure 12.85. Electric motor suppression
Figure 12.86 Ignition coil suppressor and ignition distributor shielding - indicated by arrows
If interference still exists after you have taken all of the steps above, first evaluate how much interference it is causing to you, since the human ear can easily become unresponsive to unwanted noise. However, if you are determined to completely eliminate the noise altogether, proceed as follows.
Some "experts" suggest installing a screen between the receiver and the engine. Of course, it won't hurt, but if the entire receiver is shielded and interference still exists, it's unlikely that a piece of aluminum foil will make much of a difference.
A smarter approach would be to shield the wires if you determine that interference is coming from them. First examine the power wire: interference may occur between the receiver and the inductor (this is the reason for keeping the power cord as short as possible). In this case, you can shield the wire - and here you need to buy a shielded wire and install it. It is also possible to install shielded wires leading to the speakers, although interference from them is very unlikely.
Without a doubt, the main source of interference is the high voltage ignition wires, even if they are protected. The best way to combat this is to install special sleeves over them. Since this is impractical, you can simply place an aluminum shield on top of the wires.
And finally, about the most severe cases. You can try some ways. There can be a lot of electrical stimulation where metal touches metal, so it is important to ensure a good connection. The cases in which noise from contact of metal surfaces most often occurs are listed below (in descending order of influence) - and you can get rid of them by tying up and securing the moving parts if possible:
- (A) Muffler and body
- (b) Exhaust pipe and engine block or body
- (V) Air cleaner and body
- (G) Front and rear bumpers and body
- (d) Steering column and body
- (e) Hood and trunk lid and body
These causes mainly occur when the engine is idling or under load. Although moving parts are already secured with nuts, bolts, etc., they tend to rust and corrode, thus forming a stubborn source of interference.
If you hear a muffled pulsing sound when your vehicle is moving, it may be caused by static discharge in the wheel or tire. This can be eliminated by purchasing an antistatic agent and treating the inner surface of the tires with it.
In conclusion, it should be noted that it is all relatively simple and therefore inexpensive to get rid of 95 percent of the noise, but getting rid of the remaining 5 percent is much more difficult and will require certain funds. It is up to the owner to decide whether it is worth taking such measures. Also, please remember that it is simply impossible to get concert sound from a cheap receiver.
Finally, tape recorders are mentioned at the beginning of this section: they are usually not affected by interference, but in very severe cases the best recommendations are the first three suggestions plus the use of a 3 to 5 Amp inductor in the power lead, and shielding of the power and speaker leads.
Note: If your vehicle is equipped with an electronic ignition, it is not recommended to install resistors on the spark plugs or a capacitor on the coil as they may damage the system. Most electronic ignition systems have built-in suppression and therefore should not cause interference.
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