2008 Kia Optima: Low-pitched "hair dryer" sound on AM band

____________________ I know what the answer is already, but I'll ask anywho: A shop I spoke to Saturday suggested some type of "AM booster". If such exists, would it work, or will it simply boost the noises along with the weak signals?

-CC

ground the antenna and

not firmly seated

I puilled the radio out of my Kia Spectra 3 weeks ago for a similar problem. It was fairly easy on the Spectra. The plastic in front of the radio pops off and 4 screws held in the radio. The Spectra has a whip antenna on the LR quarter. I had already checked that and found it to be ok. The coax was plugged into the radio ok. A new antenna wire did not help. AM volume is up and down. FM and CD is great. That means the radio itself is bad on my car. Someday when I have time I'll pull it out and signal trace it.

On AM a signal amp can work BUT like any other amp it can also create problems. A signal close to the one you want may get enough amplification to overload the receiver on the channel you want.

What I would do is pull the trim and pull the radio. Then hook up a better antenna and see what you get. OR pull the rear trim and locate the antenna coax from the rear antenna and see if you can break it there. It should have an inline connection to allow for glass replacement.

clip ground the antenna and

coax is not firmly seated

ok, then get a portable radio near your car and turn things on and off to discover the source of the noise, if inside the engine, then better bonding of the hood to the chassis can sometimes help.. the good news about AM is that since the frequency is low and the wavelength so long, the bonding wires do not need to be very short, even a 1 foot long bond wire can be helpful

get the ham radio ARRL handbook and look up the section about mobile operation.

Mark

But..... you didn't find the noise. Keep pulling fuses until you find the noise.

If all the fuses out and the noise remains, it's a fusible link driving the source.

Also... bring an AM radio into the car... do you hear the noise on a portable radio? Do you still hear it with the radio fuse removed? Something on the radio circuit could be an issue.

It's not a bad connection, it's some electronics spewing RF.

--scott

Yes. Find the noise source. Until you find the source, nobody can give you any good advice about what to do about it.

--scott

You forgot "crappy radio." Since AM is not a huge market these days and is ancient tech, a lot of radios have an AM section that costs about $0.27 to build, and it sounds like it. I'm starting to think that could easily be the situation here.

ground the antenna and

not firmly seated

and found it

bad on my car.

Does the "hairdryer sound" change in pitch or volume with changes in the vehicles RPM? If it does, suspect the charging system, more than likely the alternator/regulator unit or the noise suppression caps on the alternator terminals as they exit the housing, if your car has one. Sometimes the noise suppression and voltage regulator are a single package inside the alternator housing. Could also be one of the alternator rectifiers, which will usually show up as a high charging voltage measured at the battery with a digital voltmeter. (approximate: 16-19v). Or as a short that blows a fuse as soon as the ignition key is turned to "on".

To eliminate or prove the issue is charging system related, temporarily remove the drive belt from the alternator. If the noise is gone w/engine running it is on of the possibilities in the paragraph above. If the noise is still there I would suspect either the ECM or ignition electronics or a bad ground.

It could also be that your radio has a poor/nonexistent noise suppression capability, which could be remedied by putting add-on suppression caps either on the +voltage supply to the radio or on the terminals of the alternator, the most common culprit.

Good luck and best regards, Joe.