Quote:
Originally Posted by MHM
I’m hoping somebody can help me at this forum. I know it’s not the exact topic but there seems to be experts here. I've got a top of the line 08 SUV with the InfinityŽ CD/MP3 changer audio system w/ subwoofer & external amplifier and roof mount short antenna. However, the AM reception is terrible and the dealer is currently refusing to address the issue. I’m trying to build a case for them to fix it. I’ve found radio signal strength maps at radio-locator.com that show the signal strengths of area stations. The maps show the 2.5, 0.5, and 0.15 mV/m contours respectively (of the horizontal groundwave propagation only). I would like some clarification if you can provide it with respect to what signal strength I need for good reception in my car.
Should a 08 with an Infinity system receive signals in the 2.5 mV/m range without any problems? Should it receive signals in the .5 mV/m range without any problems? How about at .15 mV/m? I’m not getting good reception within the 2.5 mV/m range. (Note: I understand AM reception fluctuates with the weather and nearby interference, but I’m not talking about that.) At about what signal strength (mV/m) should I start to experience issues since in some cases there is a large gap between the 2.5 mV/m and .5 mV/m contours?
The dealer has been trying to tell me that since few people listens to AM anymore, the stations haven’t invested to keep their signal strength up to the max and nobody gets good reception anymore. They are also telling me that HD radio is causing the problem but I’m experiencing the problem across the dial and the symptoms don’t match what I’ve found on the internet. I’ve been amazed that they can make statements like that with a straight face.
It should be noted that I get more noise on the radio when tuned to a weak signal with the engine on but it’s not the high pitch noise that changes with engine speed. I also get additional noise sometimes when passing under residential power lines. I’m not talking large power distribution lines, I’m talking about local neighborhood power lines.
Thanks for any help you can give me.
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Ask your dealer to provide you with the radios' specifications, from the factory Service Manual. It'll tell you what the sensitivity of the unit is. Typically specified NOT as mV [milliVolts], but as microVolts. Any Radio Shack dealer can show you the symbols for milli versus microVolts. A radio only having sensitivity in the milliVolt range is totally deaf. Your unit should have about .25 microVolt or less [less being better] sensitivity rating. You could take your vehicle and do an A/B comparison with another comparible vehicle, as a rough cross-check. Dial in the same stations, etc. You could also use a portable radio scanner.
Any electronics shop, that services radios, can connect their Service Monitor to the antenna (1st point) or to the antenna input jack of the radio (2nd point) and input a substitute test signal, of known parameters. By 'dividing/conquering', it'll confirm 1 antenna issue, 2 cable issue, or verify if the radio itself has developed a problem requiring servicing. (the dealers technician should be able to perform basic tests). The dealer comments sound like pure unadulterated BS to me, based upon the fact I've been professionally servicing radios for over +50 years now. Engine noise can be generated by many sources. Varying high frequency whine, could be alternator related [removing the fan/alternator drivebelt and do a short duration test.] No belt=no alternator noise. Electric fuel pumps, radiator electric cooling fans, etc, pull the fuse for a brief test. Again, no operation, of a given device = no noise source. Other electronic devices have their own unique 'noise/sounds' heard on a receiver. Turn signals, windshield wipers, horns, computers only generate noise while activated, for example. Use a portable AM radio tuned to a blank spot with-in the lower half of the AM band, and do a 'walk-around test', holding it near the vehicle. Symptoms may change as you get closer/further away from the noise source. A bad electrical bonding of the hood can reduce the shielding effect of a properly bonded hood [little difference between when the hood is closed versus if open]. Defective OEM noise suppressors could have developed. Our deteriorating utility systems are notorious for producing increasing amounts of unwanted [and unnecessary] interference. The utilities are required, by FCC regulations, to address noise complaints [don't expect rapid response]. I've only touched on the most common sources. Good luck, and let us know the end results.