12V audio question

I have had some really bad noise on my AM band and thought it was the antenna, because when the antenna would move signal quality went from bad to worse. In addition to the poor AM reception and noise, say for example I have the ignition on and the drivers door open, the door ajar annoying beep thing is being heard through all four speakers.

I purchased an amplified antenna and have it connected properly with good ground connections but still have horrible noise and poor reception. I have run fresh positive and negative wires directly to the battery and the noise persists.

Can a signal problem and noise problem come in through the speaker wires, and if so would it be heard on all the speakers? Short of replacing the deck which I don't really have the money to do, is there anything I am missing?

The amplified antenna is probably the cause. You really shouldn't need an amplified antenna for a car radio. Dump that thing and put a regular antenna on and see what happens, even if just temporarily. Or did it do that before the amplified antenna? And yes, make sure your grounds are good. It is also best practice to run all your grounds to one point on the chassis, and use braid, not wire, but that's just best practice.

Otherwise, your radio may be about done.

The radio exhibited the same problems with the factory antenna, so I purchased a universal antenna more or less to test and see if that was the problem, which it was not. Since the first post, I swapped the alpine unit from my miata which performed fine, into the other car and still have the same noise.

Given that the system as a whole has the same problems no matter which head unit is running the show, I am starting to believe that there is a hiccup in the wiring. Can a speaker wire pickup noise from other sources and feed it to all the channels?

Well, "nothin's impossible." But... Unless you have a really bad, noisy electrical system, I'm thinking you have some type of wiring issue. With the power and ground run directly to the battery, engine off, you get poor receiption with any antenna you use, from a factory to an un-amplified universal, and with either head unit? I think you have a bad ground, maybe between the battery and the chassis or between the chassis and the radio or chassis and antenna. A lot of the time, if you have a really weak AM signal, you will hear noise from things like the seat belt buzzer, etc., picked up and amplified and fed through the whole system. It is still there with a strong signal, but the strong signal overpowers the weak noise so much you don't hear it. This isn't a fiberglass car, is it? Everything's different in those.

try changing the speed of your heater blower fan while listening to the radio... If the noise changes with the blower fan, it could be just bad general grounds. I got that problem in my civic.

There is usually a capacitor inside the alternator (and in just about every automotive electric motor made) for just this kind of problem. If it's gone kaput (and some cheap rebuilds leave them out) it's possible to mount one externally. Generally it's an (IIRC) 22 microfarad capacitor which has the body grounded to the alternator case and the lead connected to the BAT + terminal. This quiets noise in the charging system. There are noise filters that can be installed in the power leads to the radio but I have had less than stellar results from those. Better to zap the noise at the source.

EDIT: I prefer Alpine and Kenwood mobile electronics because unlike many of the low and mid priced brands Alpine does not scrimp on that kind of stuff. Since you swapped an Alpine and have the same noise, I lean more and more toward adding a capacitor to the alternator. One other thing to check: make sure the antenna base is grounded. If it's not, the coax shielding is useless. Make sure the radio itself has a good ground as well.

Edited again to fix a stupid word.

I have an issue with my car picking up the sound of the ingnition so it must be a common thing. They make filters that are suppossed to dampen interference but I don't know if they work.

The car is a 94 civic, the noise problems showed up independent of any repairs or changes to the car. The radio is picking up power line noise, ignition noise, and door/ignition beep noise. I've recently cleaned the engine grounds and headlight grounds. The problem exists when the ignition switch is in any position.

bigbrainonbrad wrote: The radio is picking up power line noise, ignition noise, and door/ignition beep noise.

If you are getting internal noise(ignition) and external noise (power line) this points to the antenna. Check the antenna base for proper grounding and also check the cable from the radio to the antenna base.

If the car was repainted the antenna base may not be making metal to metal contact with the roof ( or fender). If the cable has been kinked the shield braid in the cable may be broken and no longer shielding.

My radio chatters when it's cold. But then, so do I.