Power supply noise in my car stereo

[W5BRM]

Hi Guys. Ain't been on the island for a few months. Been busy with work and other projects and issues.

Got a question that is sort of ham related. I have in my truck a 100W 12vdc to 120vac power inverter. I use it to charge my cellphone as my cp has an issue with standard 12vdc cigar lighter plugs. (Samsung Moment with Android 1.5 from Sprint). The power inverter works well. The issue I am having is this inverter is a very noisy piece of equipment. It's putting buzz in all my audio stuff I have in the truck. My 2m rig, my truck stereo, my phone audio when i play mp3 files with it etc. I know I can get toroid cores to fight the issue but I am uncertain which type to get. I know i need to get the snap on ones in plastic cases as I will be putting them on power lines and speaker lines.

What sizes do I get? and does anyone have any links to a preferred supplier? Which lines do put them on? I have a standard audio patch line 3.5mm stereo male plug on each end that i run from phone audio out to aux input on the stereo. Do i put a TC on that line? I figure I should put one on the power cord leading from the 12v cigar port, one from the power inverter to the phone. What about the stereo speaker/power lines? Do i put one around the bundle where it leaves the back of the stereo? (if i can even get to it, it's locked behind the dashboard where the company says NO GO) I know i should put one around the power line to the 2m rig.

I do know one thing that is a major part of the problem but I can't change it. The location of the power inverter to the stereo. The inverter is in a little cubbyhole directly underneath the stereo. there is about 4 inches of empty space between inverter and stereo. This is where it has to stay as I need to keep my phone on the charger at all times due to extremely poor battery life issues. My phone has to stay by me as dispatch calls me frequently for updates on work. This phone eats battery life like it was a starving man at a buffet. Battery life is about 2 hours from full charge to fully discharged and the phone turns off. This is the 4th battery for this phone and it's a known issue according to Sprint. In retrospect, the toroid cores may not be the answer to my problem. Is there a way to shield this power inverter to prevent it from emitting interference?

Any input will be appreciated. Thanks. I can answer any questions when i get chance to get online again which may be a few days.

Thanks

Brian/N2NKW

[kf0rt]

I would find a way to ditch the inverter. These things are normally very noisy, and most of them are very cheaply made. Low end inverters often output square waves which (if so in your case) may well be the source of the noise.

Can you use a cigar plug at all? If so, it'd be easy to wire a cigar jack (with cord) directly into your truck's 12V. Guess I'd be interested in WHY the cellphone has a problem with cigar jacks -- this is what I use for charging the phone in the car and I've never had a problem.

I'd try to keep AC out of the equation if possible. Even as a kludge, you could buy a cheap cigar plug charger and hard-wire it to the truck's 12V. These can be found new on eBay for next to nothing -- Chinese knockoffs, but they do work. I recently bought 2 AC adapters, 2 car adapters and 2 USB cables for an iPod Touch for about $11 including postage.

This doesn't answer your question about using toroids, but someone here will have a better idea on that. I've had limited success using toroids for noise, so am probably not a good source for that information.

[N4VGB]

Inverters are infamous sources of noise, really good inverters are rather pricey. I'd take a look at the inverter output on a good scope and if it's as bad and far from sine wave as I think it is, toss it. Some inverters have output so trashy and full of harmonics that I'm surprised they don't ruin things powered from them.

I had a terrible noise problem in a '93 Chevy truck that developed slowly and I could never trace down. Turned out to be an alternator bearing going bad. :oops:

[K7SGJ]

I had a somewhat similar problem. I found going to a different inverter made all the difference. You could actually hear the change in the inverters whine as it was loaded more or less. I went with another inverter with a lot of head room, I'm thinking the load didn't bog the inverter to the point of all the oscillation which I figured made for harmonics and all kinds of hash. Short answer the newer design inverter with higher capacity made the problem go away. Good luck. Sucessful suppression can be a Royal PITA.

[w3bny]

I would echo the "get rid of the inverter" as well. Cheap inverter is cheap. And square wave as well. True sines can be pricey. Well not "un affordable" A good xantrex 600w true sine is about 170 bucks

http://www.boatersworld.com/product/MP8 ... rce=google (http://www.boatersworld.com/product/MP82318961.htm?utm_medium=productsearch&utm_source=google)

but as for your ferrite question. Mix-31's are pretty much acceptable as the norm. I kinda prefer 60's but thats just me. Anyhow normally wind 3~4 times each side then snap it closed. Another thing you may wish to try is a system noise filter (basically a good sized 50WVDC (or within reason) electrolytic cap going from pos(+) to ground which should take care of all your noise problems.

But it really does sound like the inverter you have is krazap and you should either, address why the celly charger dont work or in lieu of that, get another (mo better) inverter that isnt a noise generator.

[N9FE]

Get rid of the ciggy plug.. And ground, ground, And ground some more.

[W7XF]

Yup. Get rid of the cheap inverters. I have to have one in the truck cuz both the co-driver and I use CPAPs. When he goes away next week, I'll be able to keep the inverters off during my drive time, which will make HF so much more enjoyable again :D :D I am looking at possibly getting one of the true-sine inverters once the truck is to myself...probably 1000W or thereabouts... I know Fry's sells them, and yes, they aren't cheap. But with no experience with true-sine inverters, I don't know if the noise problem will go away or not.

[WØTKX]

I don't own one, but pure sine wave works, it's a favorite of serious VHF/UHF rover dudes.

Inverters are today's dynamotors. Noisy ones suck, yeeech.

[W7XF]

I really don't need much of an inverter; my CPAP only pulls 110W....but also I have to keep both laptops charged (Windoze one for truck stuff, MacBook for everything else). And the flat panel 19" TV I'm looking at is under 100W.

[WØTKX]

Samlex has gotta sine wave solution for about $150

http://www.weisd.com/store2/SMLPST-30S-12A.php

Other models too... I like Samlex stuff.

http://www.samlexamerica.com/pure_sine_wave_inverters.htm

[KA9VQF]

I have probably the cheapest Audiovox 75 watt inverter made. I know it was the cheapest Wallyworld had that day.

My daughter has a much larger one that has a cord so you can put it on the floor or somewhere else in the car. Hers has two outlets and is rated at 500 watts.

She bought hers at home depot {for a lot more money than I paid for mine} to run her laptop before I rebuilt the battery pack and now to recharge her cell phone and lappy when she goes to visit her boyfriend.

I got mine to run my laptop.

Hers will make noise in her stereo than my super cheap one does not.

There is a little fan that is starting to get a little noisy in mine tho. If I’m driving somewhere I can use the wall wart to recharge my phone if I so desire but I also have a cigar lighter cord for the cell that works FB.