Noise suppression
 

I have a very expensive head unit (installed by a audio shop) that the previous owner had paid for.

The CD sound is awesome but the radio is useless, so much interference.

I would have thought in the past 15 years this would not occur any longer, given the quality of most electrical components on cars these days.

What do I check for first to overcome this?

(When I was a teenager we use to put noise supressors on the coil and ensure we had plug leads that were 'noise suppression' labeled. That was tooooo long ago, and I would have thought modern electronics would be more advanced. Please correct me and advise as necessary)

Thanks
Mark

Mark,

Just a couple of shots in the dark here. First, does the car where you have the interference problem have an in-glass antenna within the windscreen? If so, have you verified that when the PO had the head unit installed, that the shop hooked up the power wire to the antenna booster of the car? If they hadn't worked on too many Porsches, they may have not known what the wire was, or which wire out of the head unit to hook to it. One would think that if your radio reception was weak due to such a situation, then electrical interference from the engine would have more of an impact on usable signal.

Second, many times with 2-way radios the interference is coming directly in through the power cable to the radio. In most of the 2-way installations I do, I put a noise suppressor coil in line, near the radio.

Finally, are you able to pinpoint the source of your noise/interference? A whine which varies with engine speed (typically alternator), or other? It might be worthwhile to determine its source (or at least be able to explain what it sounds like and what it does with RPM changes) and get to a local car stereo specialist for their recommendations.

Good Luck,
Tom

P.S.: Check out the new line in my signature.

Use of non-resistor spark plugs could also result in addition interference.
Also using different head units in the same car has different levels of interference. Which could vary from none to absolute annoyance even with suppressors (i.e. unit sensitive, some are more than others). I suppose one can always prove this if access to another unit is available.
Placing a signal cable to the amplifier too close to a power source could also induce interference.
Things mentioned could cause signal interference which should happen even when you are just playing CDs (try turn the volume down and rev the engine and listen carefully). If it really is only there when the radio is on, then it is more like a reception interference rather than a signal problem. I suspect you should then concentrate on the antenna side of the system in search of a problem.

Thanks guys. I'll get on to your suggestions shortly.

Cheers
Mark