| Author |
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Bryan
| | Posted on Thursday, March 07, 2002 - 03:21 pm: | 
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I just got a handheld CB and I notice when I use the lighter adaptor for power the CB picks up the whirling noise of the motor. I am guessing it is the alternator that is sending the noise. Do they make a filter that can go between the lighter socket and the power cord to the CB that will stop this noise? On batteries it doesn't maker the noise. Thanks..
The CB model is a Cobra hh-38 wxst. Got it for $26$ on Ebay so I hope I didn't get ripped off... |
eburrows
| | Posted on Thursday, March 07, 2002 - 03:29 pm: |
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Go down to radio shack, and pick up a couple of clamp-on ferrite beads. They look like plastic boxes, split open with a black ceramic inside. You snap these over your power line, and they'll suck off any non-DC signals. Get the smallest one that'll fit over your wire. If you really get into it, split your power wire so you can put one or more on each one. You can put both the + and - wire through the bead, and that'll work, but doing each, individually is better.
Unfortunatly, CB is an AM signal which is very sensitive to noise. Alternators, spark plugs, street lights, other big engines all interfere with it. Cleaning your input power is the best start. |
Paul T. Schram (Paulschram)
| | Posted on Thursday, March 07, 2002 - 03:35 pm: |
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No, you didn't get ripped off.
You are hearing a number of different noise sources. Some may be easier solved than others, depending upon how much time and money you wish to spend.
First off, is it a whining, or a popping noise?
The whining is the Alternating Current component of the alternator's output (referred to as ripple frequency). This can sometimes be solved by placing a filter circuit in the input circuit between the source and the load. You can buy one at your local thump-thump stereo store, or even Wal-Mart.
The other noises are radio frequency that is emitted by virtue of the spark. Old time amateur radios used spark gaps to generate the RF and they made a whole lot of noise (how's that for an understatement?). Quite unfortunately, this noise is much more difficult to rid oneself of. If you have ignition noise, you would do well to look at the age of your secondary components in your ignition circuit, dist. cap, rotor, wires and plugs. If any one of these components is not perfect, it can generate RF interference. You may find that you have to bond each body panel to ground as corrosion between dissimilar metals can cause problems also.
Usually, the best way to avoid much of these problems is to run a power cord (shielded, preferably) directly from the battery to your radio. If you decide to try this, do yourself and your insurance company a favor and fuse both wires at the battery and at the radio.
Paul |
Bryan
| | Posted on Thursday, March 07, 2002 - 05:26 pm: |
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It is the whining noise. Gets louder as the engine revs. Thanks for the input. |
Paul T. Schram (Paulschram)
| | Posted on Friday, March 08, 2002 - 08:58 am: |
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Definitely alternator induced. Fortunately, this is the easier of the two to correct.
The ferrite chokes might help, however, the frequency with which we are working here may be too low and the specifics of the cores might (Permeability, that's the term) not work at these frequencies. The noise filter kits you can buy at Wal-Mart or a stereo shop consist of a choke and a capacitor, both of which serve to smooth out the waveform.
Shouldn't be too hard, nor expensive to fix.
Paul |
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