Questions About AM Quality on My Car Radio

[Gregg]

I've recently bought a 2006 Hyundai Elantra. It has the original AM-FM cassette radio. The AM sound on the car radio is pretty bad. The radio picks up the signals pretty well. When the car is stopped I can get fairly distant AM stations. But the noise is very high when moving.

Even when the station is strong, car noise comes in whenever I go under an overpass or even a large overhead sign. If the signal is distant, the noise almost makes the station unlistenable. The FM sounds fine, no noise and good reception.

Any suggestions? I'm not sure if it's a problem with the radio or the engine doesn't have good noise reduction built in. Would it pay to replace the radio with something from e-Bay? Or whatever radio I put in will have problems on AM?

Thanks for suggestions.


Gregg
[email protected]

 

[WNTIRadio]

Put at least one ferrite choke on the power lead to the radio. Another on the antenna lead, and run the speaker leads through one as well. That should get you started.

Rat Shack used to make an isolation transformer or some kind of ignition noise suppressor. It was probably just a box with ferrite chokes in it that they overcharged for.

You can also get better spark plugs too.

Does the noise rev up and down with the engine? Do the windshield wiper motors and windows get into it too?

 

[BobOnTheJob]

In addition to WNTI's good advice, might want to remove the antenna from the car body and clean the point where the mount grounds to the vehicle. Corrosion there (and it's resulting lack of a good ground) is something I've seen cause a huge amount of AM noise when the car is in motion--yet it has surprisingly little effect on FM.

 

[boiseengineer]

Car tires nowadays can build up quite a static charge. Drag some wire?

 

[PTBoardOp94]

I had a Hyundai SUV for a rental car on a trip to Denver. KOA sounds just about as good via skywave as it did in that car.

Isolators would surely help, but I'd bet on needing an aftermarket tuner.

 

[chrish]

Don't bother replacing the radio until you resolve the ignition and other electrical noise from the car, you will have a new radio with the same old noise.

 

[Studio1]

Does it have a telescopic whip antenna or the 'in glass' antenna on the rear window?

Those 'in glass' antennae are pretty useless. They work Ok on FM as long as you aren't too far from the transmitter and most of them have an in-line RF amplifier to boost up the levels a bit.
They're designed for use in Japanese cities where the transmitters are all mounted on the tops of buildings in the cities - so they're generally within 10 km of your car.

 

[WNTIRadio]

My Subaru has an in glass antenna on the rear hatchback. Coupled with the very selective radio; you can hear it switch IF bandwidths for an instant when you tune a weak station next to a strong one. And this is the stock 2008 factory radio. First one I've kept in a car I own. Back to the antenna, it works great on FM and also very well on AM. Since it's in the back of the car, it's away from engine noise.

It's a pretty funky pattern on the top of that window to make the antenna.

 

[secondchoice]

You can also get better spark plugs too.

Another "fix": while you are changing spark plugs, get new wires too. If you plan to keep the car for more than 3 years pay a few extra buck and get good plugs and wire.

 

[nocomradio]

Alternators. The source of many a radio noise in a car too. Especially if a lazy tech replaced the alternator at some point and didn't put the little capacitor back on it that absorbs some of that noise.

 

[wgliradio]

I'm not one for aftermarket tuners. Most have horrible than horrible AM sections with very narrow bandwidth and high levels of distortion. The FM sections aren't much better with overactive blend circuits, front end overload issues and, while they are very selective, they also have high levels of distortion compared to many of their OEM counterparts.

Add the aesthetics issues and the fact that I've seen *SOME* factory radios tuned to the specific antenna system in the car (I had this in a 2005 Focus) the aftermarket radio may not play well.

 

[Fieldtech1]

I have an aftermarket JVC deck, the AM is completely useless. If im more than 6 miles from a paricular 5kw station, I can barely make out whats being said over the noise. 1kw station about 8 miles away, cant hear a peep. FM is pretty useless too.

 

[Gregg]

Thanks for the advice so far.

In answer to a couple of questions, it has a whip antenna mounted in the back.

Even though the car is a 2006, it only has 10,000 miles on it. The seller was retired and apparently only used it for short trips. So I think all the equipment is original.

I also notice about three or four seconds AFTER I turn off the key, noise is gone and distant stations come in fine. If I turn the key on, even without starting the engine, the noise returns. Then if I turn the key off, three or four seconds later the noise stops and distant stations can be heard again. So I assume something independent of the engine, maybe a fan, is making much, if not all, of the noise.


Gregg
[email protected]

 

[GeneSavage]

One more response regarding after-market:

Most AM radios that come with the car, as mentioned, are quite passable compared to after-market AM. Back in the heyday of AM stereo, I bought a Clarion AM stereo radio and loved it to pieces... I cried the day it stopped working.

I later bought a $650.00 aftermarket head unit. (Yes, I had money to burn.) After listening to it, I determined they spent $649.50 on the FM and cassette portions, and 50 cents on the AM chip. It was HORRIBLE!!!

If I EVER have money again, I'm going for a plain old vanilla Sony deck. Two nice things about Sony: #1, at least the last time I looked, they have basically the same specs on their tuners from the cheapest to the most expensive, and #2, those specs were pretty tolerable for AM.

I have a bottom-of-the-line Sony home theater stereo, and the AM section in it is downright listenable. It may only be getting out to 6 or 7 Khz.... but that's about DOUBLE what you're getting from anybody else's AM section... and Sony's sounds less distorted, too.

In addition to all of the excellent recommendations on how to get rid of the noise, if you decide to "upgrade" the deck, I'd highly recommend looking at a Sony. Even the cheapest at your local Wal-Mart should perform sonically admirably.

 

[Studio1]

Thanks for the advice so far.

It has a whip antenna mounted in the back.

So I assume something independent of the engine, maybe a fan, is making much, if not all, of the noise.

Gregg
[email protected]

The reason I asked about the antenna was that if it was the 'in-glass' variety, they often suffer from poor signal levels, meaning the AGC/front end open right up making the tuner overly sensitive and susceptible to very low levels of interference.
We can rule that out in your case.
The key will be finding out what's running (motor) when you turn the key on. One thing that comes to mind is the fuel pump.
When you turn the key on, can you hear any 'mechanical' sounds like a pump or fan starting and running?
Whatever it is, it's generating plenty of RF.

 

[stephend2]

+1 on the sony deck.

I have an alpine deck in my truck, FM is wonderful, AM is ok at best, very narrow bandwidth, doesn't get distant stations where my wife's envoy and its factory deck has a much better AM section, FM on it leaves a lot to be desired.

 

[DudeFan]

Gregg:

First thing I would suspect is the fuel pump. Most contemporary cars fire off the fuel pump to pre-pressurise the rail and injectors before the car is started. Some, like Audi/VW's with direct injected engines, will power up the fuel pump when the driver's door is opened.

Second thing I would check is an auxiliary coolant pump. Some turbo-charged engines have one to circulate the coolant (in reverse!) through the engine and turbo to cool it down after the engine is stopped.

But the real cause of your noise is a bad ground somewhere.

 

[satech]

I also notice about three or four seconds AFTER I turn off the key, noise is gone and distant stations come in fine. If I turn the key on, even without starting the engine, the noise returns. Then if I turn the key off, three or four seconds later the noise stops and distant stations can be heard again. So I assume something independent of the engine, maybe a fan, is making much, if not all, of the noise.

Have the dealer check and make sure the ECU and electric fuel pump are properly grounded. Those are the most likely causes of RF noise when the ignition is on but the engine is not running. An improperly grounded ECU can cause the engine to cut out and stall, too -- so it's a potential safety issue, not just a radio noise issue.

Also sometimes the gauge cluster in the dashboard can cause RF noise, too -- the instrumentation is all electronic these days. Listen and hear if the noise seems to correspond to the movement of the needles on the gauges.