Radio interference

Recently, my radio began receiving interference, presumably from the engine, however the interference increases in frequency with the speed of the car,
not the engine rpm's. I've changed the plugs, plug wires, distributor cap and rotor and all body ground wires, yet the interference persists. The alternator was also replaced (for other reasons) and the replacement had no effect on the interference. The battery was also replaced after the interference began with no change noted. The radio itself was installed about 15 months ago and worked fine previously. Needless to say, I am open for suggestions.
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You don't mention year or model, but if you have an external aerial, perhaps it is not making good connection with the lead-in wire or the mount is loose?
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Wheel-speed sensor?
FloydR
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If you have the aerial combined with the heated rear window it could be -a, the amplifier/splitter connection or b, the splitter unit has died.
If you have an external aerial then earthing is usually the culprit however the noise you describe appears to be coming from the alternator and it is possible that one of the diodes have packed up or the regulator unit.
Hugh
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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On Thu, 23 Nov 2006 21:37:38 +0000, snipped-for-privacy@h-gee.co.uk wrote:

If it was the alternator or a diode therein the frequency of the noise would vary with engine rpm...
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wrote:

I agree but if the car's speed increases so does the engine's speed increase too unless it does it with the engine off coasting downhill?
If it's an auto it could be the wheel sensor that controls the cruise control but generally the wheel sensors are simply a magnet in a coil sensing the proximity of the teeth on the rotor and giving that minute pulse to the control unit. There is no power going to the sensors and no signal that could cause clicks on the radio/sound system.
There must be something else ---------------------
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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On Fri, 24 Nov 2006 17:48:38 +0000, snipped-for-privacy@h-gee.co.uk wrote:

I think you ought to trust the OP on this, as it doesn't rise to the complexity of a space shuttle launch to differentiate. If it's a manual transmission, all one would have to do is step on the clutch and step off the throttle. If it was tc trannie, simply stepping off the throttle will allow the engine rpm to drop to near idle...
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wrote:

Doesn't the cruise control pick up the signals from the back axle diff unit?
Check the connections?
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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