Electrical Noise

Hi Piusq/Gregory,

WELCOME TO PRIUSCHAT!!!

By "on battery" do you mean the XM Tao battery (and not plugged into the Prius power) or do you mean when the Prius is running on battery (gas motor not burning petrol) ?

Does the interference get worse when the ICE is running?

 

Another question:

Does the Tao make the same noise in other cars, or with home stereo receivers?

If not, then I would ask the dealer's service department what the dilly.

 

Unfortunately, this may be a difficult problem to solve. The FCC requirements for rejecting noise in your XM Tao are minimal. (This is the reason airlines need to turn off electronic gear, a few items out of 100's actually jam radios.) Please consider this a dual problem of a car that makes more EMI (Electromagnetic Interference) than usual and a radio that does little to nothing to reject EMI. The major cause of the noise is the DC/DC converter changing the HV battery output voltage to 13.5 Volts to power the Prius electronics, lights, windows, etc. This is always operating, hence it will always be present as long as the Prius is on. That said, here are some possiblities.

1) If at all possible, borrow another XM radio and try it in your car. All it takes is a bad ground wire or bad filter capacitor in the power filter. If the problem is still present then.....

2) Try the XM radio in another Prius. (Go the dealer and ask if this radio works in a Prius, and actually find out.) This "double disassociation" is very important if you get really serious about the problem. Please document everything (date, serial number and model, VIN of the Prius's used, etc.). It may seem like overkill now, but some engineer at either XM or Toyota does care, but cannot do anything if no details are preserved. If you do discover something, then you are armed to go to the service department or XM with specifics.

3) Look amoung all the battery powered items and computer cables you have in your house or at work. If you are lucky you will find a big "weight" that clamps on the end of one of the cables. This is a ferrite choke that is meant to filter some EMI. Snap it on and see if it makes a difference. http://www.tdk.co.jp/tefe02/e9a15_zcat.pdf is a data sheet of what these look like (so you know what you are looking for). I do not see this solving the problem, but if one is lying around, it is worth a try.

4) At this point it has become too painful of a science project since specific EMI filtering is necessary (but may not be sufficient) and all you want to do is listen to your radio. Since even I am too dumb to go past this point, I would see if I can charge one battery while operating with another.

 

I have a 2007 Prius and using the Sirius Stiletto. I have a low hum at higher volume. Looking for answers as well.

 

I've had an intermittent variable buzz since I bought the car, on both my XM Roady 2 getting DC from the center console lighter plug and my Ipod on internal battery. By intermittent I mean I hear it maybe once a week, and it is also short-term intermittent when it is there, coming on a couple times a minute on the day it's there. When it does it it's only for a duration of 5-6 seconds. You would think it would be a consistent problem, but it's not... most trips I don't hear it. I also have a vhf/uhf ham radio installed and do not get any interference there, High Frequency (world-wide bands) ham radio is nearly impossible in a Prius so I haven't even tried. Radio Frequency interference is darn-near impossible to track down without spending a lot of time experimenting, including installing the ferrite chokes mentioned before on both the audio wire and power wire. You might also try simply routing the wires on the other side of the car. Sounds like you pretty much covered the bases already though, the device itself might be picking up the RF. If you are using an external antenna, try wrapping some aluminum foil around the unit itself and see if it helps. That would tell you if the circuits in the device are picking it up directly. Good Luck and keep us posted!

 

<div class='quotetop'>QUOTE(piusg @ Jun 21 2007, 12:29 PM) [snapback]465880[/snapback]</div>

Just modified my post... it also does it on my Ipod. I almost never use the cd player/am/fm... wonder if it's coming directly from the sound system? Some day when it's there I'll start up a cd and see if I still hear it.

 

I have the same problem. My wife's TAO works great in her first generation Prius, but makes a horrible high pitch noise in my 06 Prius. My first generation XM raido works great in both of our Prii.

 

Not sure at all about XM, and whether this solution may help...

But I had the hum CONSTANTLY, when using my iPod plugged into the AUX jack, and powered by the AC outlet in the armrest.

I believe it was Darell (forgive me if it was someone else!) that had a post elsewhere here, mentioning using a ground/line noise filter---I ordered one from Crutchfield (Item# 127SNI135), it arrived 2 days ago, and the difference in sound quality is astonishing. Here's the link, hopefully:

http://www.crutchfield.com/S-1zvxmCtoCf5/c...amp;i=127SNI135

 

I've seen 12V power noise filters at Radio Shack. These solutions will work well if you don't connect the device to anything else, but when you connect the audio output to the car's system you -could- reintroduce the noise on those wires. I suspect the Crutchfield one would solve that problem.

 

Hi folks.

I just purchased a Roady XT for my 07 Prius. I am having the exact same problem. High pitched, horrible noise when using the AC adapter when using the AUX jack. Also, the FM modulator seems too weak to get a good signal to the antenna (unless you hold your hand on the XM radio, then it works ok :blink: ). I tried another XM portable radio that works fine in other cars, same result. I plugged in an IPOD to the aux jack without using the AC adapter and it worked perfectly, no noise. I love the car but this is very disappointing. I live in a small town with 2 radio stations....this is gonna be torture.

 

I have the same problem with the ipod in the console AUX jack. High pitched sound. Haven't worked it out yet.

 

I had a similar noise problem in my Prius with a Delphi SkyFi 2 XM radio. What worked for me was a Radio Shack Ground Loop Isolator, part #270-054. This is similar to the one Crutchfield sells that was mentioned by another poster.

The Radio Shack model comes with male phono plugs on each end, plus a phono to 1/8" adapter which will plug into the aux in jack on the Prius. I had to buy another phono to 1/8" adapter to plug into my XM radio.

The problem is caused by a small voltage difference between the ground connection at the aux in jack and the ground (negative lead) of the 12 volt cigarette lighter jack. This small voltage causes a small current to flow in the shield of the audio cable, which in turn generates a small voltage between the ends of the audio cable. This voltage (or noise) gets added to the music, so you hear it.

A ground loop isolator contains a couple of small transformers which couple the signal magnetically between the input and output. There is no wire between the input and output, so no current can flow in the shield of the audio cable.

A ground loop isolator isn't likely to help if you are using a modulator to send the signal to your FM radio, nor if your audio device runs on its own internal battery. It will only help when you are using the aux in jack of the Prius AND plugging your audio device into the 12 volt cigarette lighter jack.

Hope this helps.

 

<div class='quotetop'>QUOTE(Suna @ Jul 11 2007, 10:10 AM) [snapback]476810[/snapback]</div>

I just tried using this part from Radio Shack and everything works perfectly now, thanks alot )

 

Thanks for the helpful explanation.