Car Radio Noise

[Steve_Green]

Two inquiries here.

I'm sure one has been discussed before on this forum, but myself (and perhaps others) can use an update on it because it's been fruitless locating the discussion so far.

The second topic is a puzzler.

Seems my latest 'station car' is a 1992 Mercury Topaz. A glorified Pinto, really. It has a wonderful, tight, dense, stock sound system for AM-FM and casette. Except, well, for the AM in the daytime.

The engine noise comes through horribly, swarming and buzzy and insidious. The noise parallels the RPMs as the automatic tranny goes through its thing. Enough annoying residual engine noise is there even when I'm coasting downhill and giving it no gas. The more gas I give it, the worse the noise regardless of what gear it's in. When I'm parked, engine off, and listening with the key in Accessory in broad daylight, the reception is crystal.
Is there a device that's gone fooey in the sound system which I can buy and install?

But then there's Part two : Why is nighttime AM reception in the same car so much clearer and static-free, amid the same driving techniques? As early as sunset the reception and sound starts to get terrific. From sundown to sunup it sounds as thoough the radio is behaving the way it was designed to sound. While I drive in the exact same places.

Is there THAT MUCH man made noise between dawn and dusk to affect conventional AM reception, most of which vanishes at sundown? Is skywave reception in the car from, say, WHAS, more formidable in dB to soar through the same engine noise than groundwave reception from WKOK Sunbury -- 10,000 watts omni day, from maybe 25 air miles?

 

[rbrucecarter5]

Two inquiries here.

Corrosion on the antenna ground, that is aggravated by the heat of the day.

 

[mimo]

Mercurys and any other ford product are absolute crap when it comes to AM radio reception. I have never driven one that didn't have the engine noise you mention. You did say that the noise decreases at night. Try switching your headlights on during the day and see if that makes it quieter. I had a car that I had to drive around with the headlights on during the day just to get complete silence on the AM dial. That started happening when the car was 10 years old.

 

[Mid West Clubber]

I too have a POS Mercury topaz, same year 92... Am recpetion when driving day or night is horrible for me, but the fm is actually really good, except for a very slight Engine Buzzing noise that happens on fringe area stations while driving, but is absent while the car is parked.. My dads 99 ford contour does the same thing.. Daytime AM Reception while driving=horrendus.

 

[dxho]

I found in both my cars that disconnecting the ground of the power supply cut noise way down on AM. They both ground through the antenna.

 

[Mid West Clubber]

I figured that would help, but I dont wanna hack into my electrical system, I always break something. I usually only listen to FM which is fair enough for me, I get Long distant stations from nearly 100 miles away at most times. I usually only use AM to DX, and usually in Winter when their is snow on the ground,,,, During our Harsh Indiana Winters, KOA Denver booms in loud and clear most nights,,, Yet I can barely hear WLS and its only like 150 miles away,, The other Chicago AMs come in pretty good here day and night,, Usually 720 WGN, and 780 WBBM are the easiest AM catches, but also 670 The old WMAQ comes in good most the time, I have alot of trouble getting WHAS here, and its only 90 miles away, I have trouble with 650 WSM too, but WSM used to blast in here, its less than 300 miles away, yet I can drive 3 to 400 miles north and get WSM really clear up in Michigan and Wisconsin....WEIRD AM Skywave patterns....IDK,, I cant figure out why I can barelky here WHAS here, but I can drive out to the middle of Kansas and here it just fine...LOL...IDK.... I think im right where the Skywave and Ground Wave collide for WHAS and WLS,, I once had WLS clear as bell down by Miami Florida, but now all I hear down there is spanish from Cuba or Mexico.....SUCKS>>>>>>

 

[Steve_Green]

Wow, I wish I knew which cure came first, hi.

First off : Thanks for the advice, folks.

I put in four new spark plugs two days ago ... not as a DX cure but because of the car's chugging. The plug nearest the battery looked positively gangrenous, like some sort of Jurassic encrustation. The rest of the plugs were sort of oil-streaked but had what looked like the original Autolite gappings. The buggy runs very smooth now.

But this very morning, I had what I thought was a dead battery but turned out to be a frazzled Red Lead to the battery. After a cleaning of the terminals and leads, and a few oaths, the battery connections are almost up-to-par for a Ford 4-popper (the showrooms of which ask you where you'd like your rust put).

Bottom line : The AM works as good as it ever did. The real huge, all-pervasive noise is gone.

* * * *

To the soul who suggested the headlights on during the day : It seems to work half-and-half. Sometimes the headlights cleared it up ; sometimes they didn't.

Thanks again, folks. I haven't gotten around to the antenna corrosion part or the defeated ground part yet.

 

[Tom Wells]

The battery is actually a huge "chemically active" capacitor.
In the old days, hams took old dead car batteries, filled them with oil, and used them as filter capacitors for power supplies.
So a high-resistance connection means that most of the power to the radio was "straight off the alternator", with all the noises from the various loads appearing in the DC available to the radio.
With a good connection they disappear, because the battery is a bypass path for the AC in the system.
I wonder what a battery's capacity in mfd. would be?

I doubt plugs would make any difference in radio noise. Changing out bad plug wires can help with popping ignition noises.

A bad battery connection due to corrosion has intermittent effects.
I too, had to clean up battery posts on one of my cars wednesday afternoon while on a trip to Indianapolis.
Maybe it's just the season for battery corrosion.

 

[rbrucecarter5]

I put in four new spark plugs two days ago ... not as a DX cure but because of the car's chugging. The plug nearest the battery looked positively

But this very morning, I had what I thought was a dead battery but turned out to be a frazzled Red Lead to the battery. After a cleaning of the terminals and leads, and a few oaths, the battery connections are almost up-to-par for a Ford 4-popper (the showrooms of which ask you where you'd like your rust put).

Believe it or not - a lot of shops will not gap spark plugs. They just slap 'em in there. If they see a gap, they think good enough. You would be surprised how many times I've seen that happen over the years. Properly gapped, they not only have less interference, but the car runs smoother and has better gas milage.

Another incredible thing I've seen. Some people still think copper - not resistive carbon - spark plug wires give better performance. One time someone complained to me about interference, they had bought the car used from a kid who dorked with the engine to make it a street racer - and yep, the spark plug wires were copper - and the thing radiated RF interference for a block. I'm surprised the FCC hasn't cracked down on that nonsense - and that people still think it gives more power. The reverse is true, and it burns up the ignition coil(s). They aren't designed for the current from the back pulse.

And yes, the battery terminal corrosion problem can cause horrific interference. The person inventing side mount battery terminals should be taken out and SHOT. Seriously. You can't jump start the car - at least as easily - and it doesn't do anything to stop corrosion. I do have a wonderful fix, showed to me by a really wise old mechanic. Get everything cleaned off (side or top mount). Don't use a wire brush - it creates scratches that are more surface area to attract oxygen and corrosion. A solution of baking soda and water works beautifully to reverse bad corrosion - I have a little plastic cup and I dip things in it. When it stops bubbling and the water is rusty, the reaction is finished. When it is clean, make your connection tightly and securely. Then coat everything that is exposed metal at the connection with wheel bearing grease. The silicon type is best. The thing won't corrode if you get it completely covered, because oxygen can't get to the metal. I've had cars run for years with no trouble after doing this. The grease has a small water content and the metal turns black, but it is a much slower process and leaves you with a viable connection because the black stuff is still conductive - unlike the white powder. That should keep the noise from recurring. By the way, the grease also works on alternator and starter connections. But you only have to worry about the positive side.

Don't overlook the battery cables themselves as a source of interference. I had a car that had progressively worse and worse interference, and finally it wouldn't start at all. Not even with jump start. Fortunately, I was at home. Battery was charged, so it and the alternator were good. Humm - wierd. Starter was good. Wierder. Then I noticed a mysterious bulge in the battery cable. I took a knife and cut into it - green powder sifted out. Years of vibration had rubbed a hole in it, and the cable had corroded through. Replaced the cable, and the car started right up, and the AM interference was GONE!!!