rpicnic

Just inherited a '91 LS 400 with about 77,000 miles on it. My Mother in law purchased new in 1991. My plan is to keep it and drive it for quite a while. AM Radio seems to have more static than I expected. Characteristic of the car or something that is fixable ?

RA40

iTrader: (6)

Welcome to Club Lexus.

The radio should be clean sounding , does it happen when listening to FM stations? Several possibilities, antenna wire that leads into the antenna is loose or some other grounding issue with the audio system. Check the the negative battery terminal is clean and making good contact. The AM portion of the radio may have seen better tuning days though AM radio isn't the cleanest sounding either.

LScowboyLS

great advice and wisdom as always from RA40, the rest of us could take a vacation and know that CL questions would be answered expertly!

rpicnic

As a response to RA40, the FM reception appears to be excellent, the scratchy audio only happens with AM. Thanks for your suggestions - I'll try and have the battery terminal checked for it's conditon. The AM tuning seems to work fine, it's just that the audio quality is scratchy sometimes. Could it have something to do with the quality of the AM signal ? The more powerful local stations seems to be much better.

RA40

iTrader: (6)

Tuners vary so you may experiment with another radio to see how well it tunes in those suspect stations.

Thanks LScowboyLS. We have a great community here. Many contributors to help our fellow LS owners keep the cars happy.

LScowboyLS

depending on where you are and where the station is, and the weather, time of day, and ionosphere, AM reception can be noisy and suck, that is why they developed FM radio and later on Satellite radio and later on HD radio!

and just like an ECU, your stock radio has capacitors in it which eventually go bad, but most people never bother to replace them, they just get a new head unit since ours is a bit behind the times.

Kansas

Wow! I almost forget AM radio existed ... remember listening to it from the 50's into the 70's. WHB-AM = "World's Happiest Broadcasters".

I pressed the AM button on my LS radio for the first time in .... like ... forever. Scanned the stations. Most of them sounded like $#!+ with low quality sound. Won't do that again.

I don't listen to FM radio much anymore either .... mostly stream audio from the Internet via my phone to my LS400 radio: Pandora, Slacker, iHeart, Tunein, etc.

Yamae

The "FM" is not interfered by impulses and you don't get noise as long as the amplitude limiting amplifier at the IF section is working properly.

On the other hand, "AM" means Amplitude Modulation and it is weak against the impulse noise. There are several circuits that generate impulses. For examples, the ignition circuits, the fuel injection circuits, the ECU itself and others. Toyota uses 0.47uF/250V film capacitor for JDM Celsiors as is shown below ( this is for a UCF21 but UCF10/11 also has one) to reduce the ignition and injection RF energy aiming to provide better radio reception. US models are probably the same.



Mine had some problem receiving weak AM stations including the "Highway Radio". In Japan, there is a radio service at highways and you can listen to it while driving and you can get the information of accidents, traffic jams and etc. To catch them well, I did some experiments and decided to add additional ceramic capacitors as below.



There are 4 of 2200pf capacitors in parallel with the original capacitor at the left part of the photo. The reason why 4 is the result of experiments using a spectrum analyzer. To use 4 as the photo above showed a good result between 1-15 MHz.

Now I can listen to the "Highway Radio" much better than before and I even can use short wave radios in the car.

Judging from my experience, your LS400's capacitor somewhere near the ignition coil might not be working well enough. Replacing or adding capacitors like I have tried might improve your situation.

LScowboyLS

yamae - your image host is not showing up - can you use imgur.com for images?

I am excited about your AM radio performance mod!

Yamae

Sorry for the images not fully OK to view from some other route.
I just have changed the host and I think you can see them now.

Gene01

Yes, they are now visible. Thanks, Yamae-san!