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Emergency Expertise Needed One More Time Please, AM Radio Car Engine Interference

G

GekkoRadio

If you can help me one more time as I have to solve this quickly as I just installed the
Kenwood KDC-HD458u at Best Buy and I am getting engine noise interference on all AM radio
stations. I pretty sure I read on one of the threads either here or elsewhere that there were certain
brands of radio that had this problem.

I'm mad at myself for not just listening to the people here and getting a Pioneer SuperTuner. The FM worked
fine but one annoyance was that if you had the FM tuner set to analog and you were on a HD station it would flash a Digital
graphic permanently. And there was no way to remove the clock at the bottom underneath the station frequency which made
it difficult to see the top portion of the screen identifying the station.

But anyway the most important thing is the AM interference, when the car is off it comes in fine, when the car is running
you get the engine rattle interference and it seems to pick up as you accelerate. The installer seems to think that this
problem is going to be on most radios because generally the companies don't put a lot of work into the AM section.

I'm sure the people here will know of a brand that does not have this problem. Thanks for your help.
 
You need to purchase an inline "choke coil" for the +12 volt supply line. Any retailer that sells car audio products should carry these. Less than $20.
Also, make sure your engine has 'resistor' type sparkplugs installed. Lastly, tighten ALL underhood ground wire bolts.
 
Big 121 said:
You need to purchase an inline "choke coil" for the +12 volt supply line. Any retailer that sells car audio products should carry these. Less than $20.
Also, make sure your engine has 'resistor' type sparkplugs installed. Lastly, tighten ALL underhood ground wire bolts.
Click to expand...


Thanks, I will do those checks and discuss the "coil" with the installer, he seemed to pass it off as if most new radios don't put anything into the AM side and that is why this happened, I'm still concerned though with this Kenwood brand in reference to their AM reception which also sounded weak in addition to the engine interference noise.
 
Your problem might have more to do with antenna than with your radio. My new vehicle - although it has a 31 inch whip antenna - it does not terminate the coax shield at the fender end to ground. The result is alternator noise - I haven't gone into the fender to take care of it yet. Proper fender grounding of the antenna coax is key - even a bit of corrosion was enough to cause a friend trouble with KFI only 60 miles out.

Pioneer is not going to have better performance if your antenna system is compromised. I am not surprised an installer wouldn't know about this - but AM is often neglected. My "new" / old vehicle had an open somewhere in the antenna wire, and they didn't detect the problem at the dealer. I guess the Carmax 130 point check or whatever it is only includes FM. The open, of course, created capacitive coupling that worked on FM, but not AM. FM was degraded, but if local stations came through they were happy.

The choke solution might work - but I think you are going to have to end up with some big value ceramic capacitors, probably several in parallel, to filter the alternator line where it comes into the radio. But that is only conducted noise - if your problem is radiated noise it won't help.
 
rbrucecarter5 said:
Your problem might have more to do with antenna than with your radio. My new vehicle - although it has a 31 inch whip antenna - it does not terminate the coax shield at the fender end to ground. The result is alternator noise - I haven't gone into the fender to take care of it yet. Proper fender grounding of the antenna coax is key - even a bit of corrosion was enough to cause a friend trouble with KFI only 60 miles out.

Pioneer is not going to have better performance if your antenna system is compromised. I am not surprised an installer wouldn't know about this - but AM is often neglected. My "new" / old vehicle had an open somewhere in the antenna wire, and they didn't detect the problem at the dealer. I guess the Carmax 130 point check or whatever it is only includes FM. The open, of course, created capacitive coupling that worked on FM, but not AM. FM was degraded, but if local stations came through they were happy.

The choke solution might work - but I think you are going to have to end up with some big value ceramic capacitors, probably several in parallel, to filter the alternator line where it comes into the radio. But that is only conducted noise - if your problem is radiated noise it won't help.
Click to expand...


Just to let everyone know that with the factory installed radio there was no engine interference, does this rule out the Antenna, does this rule out the need for a coil/sparkplugs etc?
 
If there was no interference with the factory radio but there is with the new aftermarket thats an odd duck...though OEM factory radios on AM are not as sensitive as aftermarket brands....so it could have been there anyway...you just notice it with the more sensitive tuner...if NOTHING else has changed (and I MEAN NOTHING), I would suspect the radio myself....

but I have never ran across your situation in my 40+ years of RF...You SURE??!!!! nothing changed??? Have you tried going back to the factory radio to confirm???

MOST modern cars have ignition systems that operate at HIGH voltage levels thus the spark issue is worse but then to reduce noise across the AM and FM bands, they put certain suppressors across the DC wiring at a lot of place to keep it down..outside the AM/FM bands, I HAVE seen noise issues pop up on otherwise quiet autos (like on ham/amateur HF or lowband 2way gear)

Alternator whine that Bruce discussed of course is different and sounds different from ignition noise (pop pop pop as the plugs fire)...and from what I read, you are not experiencing that..

MOST plugs from factory are resistor style...is it possible that a plug wire has been damaged?? (open the hood and look at the engine etc in a DARK DARK area....stay safe of course!!! and look for flashes as the engine is running..that could show where the pops are coming from...only other thing I could suggest is a spectrum analyzer with a sniffer on its antenna port to really locate where the noise is coming from)

BUT I would try putting the factory radio back in and verify your statement 1st.....and then troubleshoot from there...
(probably quicker than trying the looksee).....and make REAL sure your grounds are not riding loose...
 
ContinuousWave I have to go out and listen to it again, it might be more of a pop type of sound. I am 100 percent confident there was no problem with the factory installed stereo. Actually there was one problem but not related to AM radio clarity. The only reason why I had to replace it was because when you turned the radio on, the sound would not start right away and it took longer in the colder weather to pop on.

If I could test it I would but at this point the installer has agreed to put a new radio in without charging me for a new install. I'm going to put in either the Pioneer DEH-3600UI or the 3700UI (The 3600 has an FM sensitivity of 9dbf while the 3700 has 11dbf but both have high metrics in the areas that people here told me to look for). The 6700BT was another possibility.

I will mention the information from above and have the installer look over everything and hopefully this solves it. I could have sworn I read about a certain radio having this AM interference problem but I can't find the thread or website.
 
I just tested it again, it definitely sounds like the noise in that Youtube video, I was wrong in that it does not sound like an engine and it does not get louder
upon acceleration, it is not quite as loud as the interference in that Youtube video but it is relatively constant. I'm wondering if it is related to the build quality of the Kenwood HD am section of the radio.
 
Well I just got the new radio installed, I decided on a double din Pioneer FH-X720BT, after the lead installer said there was nothing that could be done about the AM interference sound, he discovered that the installer who had put in the Kenwood did not connect the wire labeled for a power antenna because I did not have a power antenna, he wired that one in and what do you know the interference noise is gone.

The people here that recommended the Pioneer SuperTuner were correct, it definitely does the job with FM, the only negative being a lack of a true mono button as some of the weaker stations still might have some stereo hiss even when set to the 4th level of auto tuning which is the one recommended for only the strongest stations. All of the AM stations that I need, WFAN, WABC, WOR come in clear, Bloomberg radio struggles more than with the Kenwood but the clarity on the other AM stations is better than the Kenwood.

One final question, some of you wrote that an antenna can make up even more of a difference, I have a factory antenna, if I was to decide to try to increase the signal strength even more, especially for AM, what brand and model antenna would you recommend?
 
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