I always had trouble with static at left-end-of-the-dial stations (like my NPR stations). SOMETIMES, as I drove static would gradually increase until you couldn’t hear the radio at all and SOMETIMES putting it in Park would clear right the static right up. I have witnesses, although not the dealer, natch. I replaced the stock radio with one that had extras, hoping it would also be a better radio, but the reception on the new one is even worse. So I put the stock radio back in, took it to the dealer determined to make them fix the increasing-static-until-Park issue but of course the radio behaved that day and they said it performs to spec.
So here’s my question: what would make the static gradually increase (sometimes) and why would putting it into Park (sometimes) clear it up? And what parameters does one look for in a radio when one wants really good FM reception?
Well, this sounds like some sort of problem with electrical interference caused by something in the transmission. Now I’m going to have to speculate pretty wildly here, but there are some relays and a transmission control unit which might cause that sort of thing. I’d guess the TCU would be more likely. I’d say try to get this to happen at the dealer. Ask them to drive it around for a couple of days and maybe they can reproduce the issue.
Now, on a replacement. What sort of reception problem did you have with the replacement? Was it the same problem, or different? If it was a different problem and the replacement was just not a good FM receiver you can find a better one. The primary measure of ability to receive FM signals is “sensitivity” and is usually specified in dBf. The smaller number the better. There are other specs, not always published or easy to find, like adjacent channel rejection or image rejection but in general with good name brands the sensitivity rating will be a good guide.
Here is a link to an article on FM radio reception. About 1/2 way down the page you’ll find a set of definitions about image rejection, sensitivity, etc.
http://www.wwuh.org/news/recep.htm
It could be electrical…but it could also be that you’re too far away from the station radio tower. The reason it might work fine at the dealer is because they are closer to the tower. Check where the towers are and see if that’s the problem.
I like Ranck’s suggestion about the noise coming from the TCU. There may be excessive noise coming from it. If that is the case then this problem may be difficult for the dealer service to deal with. Radio frequency interference problems can cause some real problems in trying to solve them. If the TCU was the problem it would have to be replaced most likely.
Noise can also be a problem if the antenna ground isn’t making good connection. I would first check to see if that is the case. Possibly trying a different antenna even, while the trouble is occuring, and see if that makes a difference.
If the antenna circuit is ok and excessive noise is coming from something like the TCU in the car it would be nice to have a spectrum analyzer to help hunt the source down. The dealer service isn’t going to have that on hand though. Using a handheld AM/FM radio may help though. Tuning it to the noise area and moving it around and near suspected trouble areas may help pinpoint it. The AM section may be able to pick it up also if the noise is broad enough in frequency.
You noticed that FM reception is better when the car is stopped. I think that you have found out the secret. It’s bad when you are moving; especially if you are going away from the station. AM is better for travelling. You can’t get FM by switching radios. The location of the transmitter and the power it has seem to make the difference.
Make a test (we are in the testing mode here) get a magnetic base antenna and conduct experiments in reguards to where the reception is best.
Make a list of stations that work good and ones that don’t
Compare station power,antenna location,your car location,the terrain,engine on or off and see if some conclusion can be made from the data
I worked for a company that provided radio system service to Big Three Dealers,complaints about radio system performance were in the top 3 areas.
Usually the radio complaints, were about people having poor AM performance and were usually due to issues other than the radio,antenna etc, but AM is much more dependant on having a antenna.
The FM issues usually did end up being related to the radio itself.If not station,terrain,or distance issues.
Is your vehicle equipped with a signal booster? I have found them to be of very limited value,sometimes the cause of the condition.
The paramaters that you want in a radio with good radio reception are called “selectivity” and “sensitivity”, don’t ruel out the problem being with the “head units” just yet.
Is your vehicle equipped with a “standard” antenna? or is it electric,or in the defrost grid? make the test with the mag base antenna.
Had the same experience with an Explorer several years ago. It turned out to be the cable for my cel phone charger when it was plugged in. When I removed it one day the problem went away. Re-pluged it in, and the static never came back.
First, thanks for the thoughtful comments and suggestions. Here’s some additional info: the antenna is the kind embedded in the glass. I read about signal boosters, but they didn’t seem very promising so I did not install one. Behind the dash I can follow the antenna only a couple of inches. How can I find out where it’s grounded?
The new radio (JVC) has significantly worse staic overall so I can’t really tell if it does the “increasing interference” thing. Did I mention that it’s more likely to happen when it’s damp outside? BTW, I do a lot of in-town driving, so when I say the static increases as I drive, it’s a function of time more than distance. I have stopped the car in the middle of the road (sans traffic) and put the car in Park just to prove that doing so will clear the static. I didn’t want my family to think I was crazy.
I will look for fm sensitivity numbers. How can I tell what the specs are on the stock (unbranded) radio? If I can find that at least I will have a benchmark for comparison.
I might know someone with a spectrum analyzer, since I do know some engineering types who have some pretty strange toys. Will ask around.
As for the dealer driving it around for a couple of days … that’s not going to happen. This is one of those huge dealerships that would rather scoot me out with a fluid change I didn’t need than waste their time trying to get to the bottom of a problem.
Between the great article posed by Ranck and other suggestions here, at least now I feel I have a way to proceed. Thanks to all!
try running another ground to the radio chassis,the only other thing which fixed older monteros,was running a redundant ground to the firewall ,from the intake plenum (so long as its metal)or the block.
just a thought.
good luck.
Another thing to check out I didn’t think about in my first post is the position switch for the transmission shift lever. Switch contacts can make noise if they don’t make good connection. If there is a connector to a position switch you can easily remove try that.
I very much doubt replacing the radio will help you with this. A unit with a more sensitive RF input will most likely just pick up more of the noise also. You pretty much proved that with the other radio. I think you will find either the existing antenna connection is faulty or there is excessive noise coming from something connected to the transmission area. Perhaps connecting to a different antenna while the noise is happening is the simplest thing to try and solve the problem. Using a 10 foot piece of coax cable with the last three of feet of the ground shield removed away from the center conductor and hung outside the window will work for FM signals. You may need a Motorola connector to plug into the antenna input of the radio. Some RG-59 coax for TV wiring will work for the coax and is cheap. Radio Shack should have these things if you want to try that.
Here’s the thing. FM generally doesn’t get “static.” Not like AM. If you are getting noise that sounds like static and it was worse with an aftermarket radio I have to think there is either a bad ground somewhere, or noise on the power supply. That could be your alternator. Someone with an oscilloscope would be able to see that problem (a shorted diode will cause a lot of noise on the power supply, which will be somewhat mitigated by the battery recharging after initial startup, but I can’t figure why in/out of gear would change that).
The suggestion of adding a ground wire to the chassis of the radio to the car is easy and worth a try. I have had that fix problems like this.
As for sensitivity and other specs on the stock radio, they should be in the owner’s manual (possibly a separate one for your radio) that came with the car. Typically stock radios are pretty poor. There are some exceptions, but most they are cheap, lowest bidder, stuff.
The other test someone suggested, plug in a test antenna, is also easy to try and if you can borrow or buy a cheap replacement antenna you can plug it in and just have a passenger hold it out the window for the 5 minutes it will take to test.
I still say your best bet is to insist the dealer spend enough time driving the car around to hear the problem themselves. Don’t take “no” for an answer. Ask to speak to the service manager to get past the no-nothing service advisers. Don’t get mad, just be firm.
You mentioned antenna ground as a possible cause of static. I have a '96 Ford Ranger XLT. When the engine is off and I put the ignition to accessory mode, the radio plays clearly, both on AM and FM. When I start the truck, the AM channels are full of static, whereas the FM channels are still pretty clear but there is some static. How would I check if the radio ground was ok or not on this model? Where is it!! Thanks for your assistance. Staticy in Colorado!!