Pure Sine vs. Regular Power Inverters

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Apr 1, 2004
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Does anybody actually use pure sine inverters (clean power)? I've been getting by with regular modified wave inverters ever since I started chasing, but now that I'm needing to get another power inverter I'm considering getting a pure sine one for running my laptop and a few other things on it that may be a little more sensitive.
The pure sine inverters (clean power) cost literally like four times as much if not more, so it's not a real simple decision to make especially if you are looking at a 600 watt or higher power inverter.
Is anybody using pure sine inverters and what are your feelings on the matter?
 
Hey Mikey, I just got a pure sine around Christmas. I didn't find them to be 4 times the modified wave cost, but then again I only got a 180 watt inverter. I am pretty sure my laptop got screwed up from using the modified, so I went for the pure, and my limited testing of it has produced no problems.
 
The April 2009 issue of QST magazine has a technical review of pure sine and modified sine wave power inverters. I have a PDF copy of the article but it's too large to attach here. The pure sine were clearly the winners when looking at the outputs (the article shows the oscillscope traces). The article concludes:
While MSW inverters can work at an Amateur Radio station, it is more likely that pure sine wave inverters will emit little or no interference, and attached electronic equipment will be happier.
It is my suggestion that you look for a good quality inverter that matches your load requirements. Too much over-sizing can be costly, and it is smarter to buy the best small inverter than the largest cheap one you can find. No-load current draw and efficiency are important factors to consider, as they affect battery life.


Models tested
Cotek ST1500-112 PSW 1500 W continous $650
PowerBright PW2300-12-1 MSW 2300W continous $250
Samlex PST-100S-12A PSW 1000 W continuous $480
Tripp-Lite PowerVerter PV-1250FC MSW 1250 W continuous $270
Xantrex XPower 1750 Plus MSW 1500 W continuous $230

Of the MSW units, the Tripp Lite had the obvious best characteristics. It has a vertical form factor though, making it not as convenient for mobile use.

Mike
 
These are the two I'm looking at. I want at least two outlets. I've gound one 350 watt with two outlets for $225 and a 600 watt for $230 on sale, so I think I'll go with the 600 watt. I can probably run both laptops off that. Check out the site if you need a power inverter. They have everything. I would love to get one of those monster inverters (like 3000 watt) but I seriously can't imagine that working properly and what in the hell could you ever need that big of an inverter for? I could power a deep freeze loaded with popsicles, a cool zone fan and a few massage chairs out of the back of my car when we have chaser convergence.
http://www.donrowe.com/inverters/puresine.html
http://www.donrowe.com/inverters/sk_350.html
 
I've been researching big inverters (1000W+) for my RV and the data I've read says that pure sine inverters are good for really sensitive equipment such as medical devices. Most RVs use modified sine inverters to run a whole range of gear, including computers, TVs, DVD players, etc. My guess is that you would be fine with a decent quality modified-sine inverter.

Keep in mind that modified sine inverters are a step up from the el-cheapo inverters that have a square wave output. Avoid the cheap stuff as the square wave output makes things with inductive loads (transformers, motors, etc.) run hot and can ruin them.
 
AFAIK, it depends what equipment you're running. Switching power supplies, like those in your laptop, actually like the stepped waveform. (Even a cheap square wave inverter should be OK.) Radios and other analog equipment might well be better off with smoothed input; the abrupt steps may not be completely filtered out, and may surface as system noise. I'd think that a well designed system should be able to cope with either.

Tim S, you out there? What say you?
 
I am looking for some insight on inverters (dc/ac) vs. adapters (dc/dc). I have an adapter for my laptop that works in the car or on an airplane. Why would one convert dc to ac, only then to have the factory power supply convert it back to dc?
 
I've got an 800 watt Cobra MSW inverter in my truck, and when a moderate load was put on it (two laptops and a router) the RFI was bad enough that even my 2 meter FM radio and weather radio (typically noise-tolerant bands/mode) were severely degraded. Keep in mind the 2 meter isn't powered by the inverter, the inverter is physically radiating RF affecting any radio nearby.

In the Southeast, many states rely heavily on statewide HF ARES/RACES nets, frequently in concert with the skywarn operations at NWS offices. I've never found a MSW inverter yet that didn't completely destroy reception below 50MHz right out of the box.

There are a very few appliances that won't like MSW. Primarily they are PWM (pulse-width modulation) based battery chargers and such that are charging batteries with brief pulses of high voltage directly off the 120v rail.

For the purposes of those appliances, you can actually make an MSW inverter work just fine by building a nice hefty low pass filter and putting it on the AC output. This filters the harmonics of the 'stepped square wave' and essentially renders it a proper sine wave. That will also do quite a lot to help your RFI issues (really this is all a 'pure sine wave' inverter does internally) but additional filtering and shielding might be necessary for HF radio operation to be really reliable.
 
A few years ago I was having some problems with the touchpad on my laptop that only occurred when it was in my vehicle (I think someone else started a thread about these kind of issues at the time here on ST). I switched to a sine wave inverter and the problems went away.
 
Mikey....Check Camping World's website for bargains on inverters...Some new electronics/batteries see the wave form of a conventional inverter as toxic...so a pure sine waveform is the best choice...You've done the right thing by investigating the differences...
 
Mikey,

Here's a thread from the past where this topic was discussed:

http://www.stormtrack.org/forum/showthread.php?t=13245

At the time I owned a Lind 150 Watt Pure Sine Wave inverter found here http://www.lindelectronics.com/cgi-bin/store/shop.cgi/!ORDERID!/other/INV1215US1P/dbx_gen_detail_product/, but post #14 in that thread from Stuart Robinson got me to thinking about the DC adapters in general. I ended up switching from the pure sine wave inverter to a DC adapter from Lind and have been totally satisfied ever since. I can see the need for AC power in a chase tour van, but for the power that runs your laptop I'd seriously consider the DC adapter as it can't be beat. Here's a link to the Lind site where you can check out DC adapters for your specific laptop model.

http://www.lindelectronics.com/cgi-bin/store/shop.cgi/!ORDERID!/Special_DC_Adapters/x/dbx_gen_Special_DC_Adapters_mfgs/

They also have a 300 Watt pure sine wave inverter here that you might want to check out:

http://www.lindelectronics.com/cgi-bin/store/shop.cgi/!ORDERID!/other/INV1230US1P/dbx_gen_detail_product/

Happy shopping!
Mark
 
I'm trying to determine my watt usage because I am looking into sine wave inverters. I am going to be running a Toshiba laptop and the Shasta/CA-819 amp + MAK Mobile Accessory Kit from Maximum Signal (basically a antenna and amp for the mobile internet). Anybody know how much wattage the laptop and inverter would use, or do you know of a site that might list this info? I did a little internet search, and I came up with about 45 watts for the laptop but that just seemed too low. Thanks!
 
Doesn't your Shasta/CA-819 amp + MAK Mobile Accessory Kit already run off a dc outlet david?
I have always gone with 300 watt inverters until I had a 700watt installed in my car. Assuming you don't need one for you amp and the only thing you are running is your laptop I would still go with a 300 watt with two outlets so you can power up something else if you need to. I've had tons of times where I was on the road and realized I had a camera that wasn't charged, needed to charge a cell phone or does god knows what else that requires an ac outlet. Back when I first started chasing I just went to Radio shack and bought their 300 watt inverter. I've owned two of them now and they work great. I'm only looking into all this stuff on the internet now because I'm running so much crap in my car. God down to Radio Shack and just buy their 300 watt inverter. I was just looking at them yesterday and they're $60. I was going to buy another one but I know I have a brand new one still in the box that I bought last year and can't find. I wouldn't bother with ordering anything off the internet. Those best buy inverters are the best performing ones I've ever used and I've gone through four different brands.

edit - btw if you get to the point where you need more than 300 watts I'd go with two smaller inverters rather than one big one. Don't put all your eggs in one basket in case of a problem. I prefer knowing I have a back up in a crisis, but I take that kind of stuff to an extreme. If you could see the amount of crap I have in the back of my car (when I have time to properly pack) you would understand.
 
That is really interesting Mark. I had never even heard of doing that. I looked around a little bit on that Lind website and they look like a really well run and reputable place. I saved it to my favorites and I'll definitely be going back to shop around.

In my first couple years of chasing I bought a power cord for my laptop that went directly into the dc outlet. For some reason the laptop didn't get enough power it was slowly draining, which I didn't find out about until later in the day when I was about 80 miles off a storm. I've had a million different issues like that. With my XM reciever it quit working off my dc power cord so I had to order an AC one and power it off an inverter. I've had dozens of things happen like that and I almost have a phobia of feeling under prepared. I like to know I have backups for my backups.

I just like the versatility of running power inverters where I know I can run anything I need to. I think if you could see the amount of crap I keep in my car (as long as I have time to pack for the chase cause I'm always running late and the pack job takes an hour at least) you would undertand. I make sure I have a charger for every piece of electronic equipment I own in there. I also run a ton of equipment for example XM reciever, two laptops, storm hawk (which require constant power to a cell phone and a PDA), radar detector, cellular amp, video camera for streaming and an ipod (at times). There are the occaisional things like charging cell phones or bluetooth headset if I forgot to since the last chase and a lot of times my cell battery runs out if I'm in the viewing area. It's a god damn mess in there. I actually have an appointment on Tuesday to have two more dc outlets instaledd which will make 6 plus a hard wired 700 watt amp. I'm talking about my car by the way. We won't have to use a van this year unless we start booking more people quick (we started way to late), so unless that happens we'll just use my car and one more SUV if we exceed three people that day. We got started really late on the tours this year so it's been tough getting the word out with advertising. We were actually supposed to start the tours last year, but it was a joint effort with another company and it fell through. This year we are only going to lease the van from another company that does similiar trips if we have to, which at this rate I doubt we exceed the capacity of the SUV's. I was just looking through emails and noticed that we actually started advertising the tours almost exactly one month ago. Nothing like waiting till the last minute.
Next year I'll go ahead and buy the van in the November time fram so I can start working on it (I know I'll book plenty of people next year for a few reasons). I actually think it will be fairly easy to outfit that since I know through trial and error what you need and where you need it. I'm really looking forward to doing that. The van sucks ass though because you can't get on any back roads that are wet and obviously can't get as close either. That's why I prefer the SUV's.
I'm a little too long winded lol.
 
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