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Author Topic: Power Inverter noise ???  (Read 9109 times)

Posts: 152

« on: April 16, 2007, 12:32:13 PM »

The station I'm setting up is on a farm, on a meadow hill top, totaly in the clear. A Delhi68 tower, and an old travel trailer w/ woodstove.  1000ft from the house means no AC.  So I'm using 2 big marine deep cycle batteries, with a Xantrex 500w inverter.

I've noticed the power inverter makes some nasty howling heterodyne QRM on the HF rig. The tone and amplitude of the QRM changes based on what I've got plugged into the inverter.

I tried grounding the inverter chasis, and passing the power bar cord a couple turns thru a small toroid, but the noise persists.

Has anyone solved this before?  Do I need more turns thru a bigger toroid?  Heavy grounded shielding around the inverter & power cords?

Thanks for any suggestions

Posts: 89

« Reply #1 on: April 22, 2007, 12:15:29 PM »

I'd like to step back and ask why ur running an inverter in the first place. Most solid state radios run from 12V directly. In terms of operating life on the batteries, its not efficient to invert 12V to 110VAC and then drive a power supply to run a radio.

The inverter might be in use to drive a rotator, but then its use would be on an "as required" basis. Its RFI would be temporary.

I'd be doing all that I could to get the inverter out of the equation.

As for the noise from the inverter itself I know little about the subject, but I would expect the noise to be difficult to suppress due to its broadband nature (the mechanism that the sine wave is synthesized).


Posts: 3189

« Reply #2 on: May 01, 2007, 11:35:34 PM »

Most inverters do not create AC in the same manner  that a normal electrical service might provide.

Some brands of inverters are "noisier" than others.

The RV community use inverters and it's not unusual for them to install a power line conditioner to clean up the AC sine wave.

However, sometimes it's just cheaper to buy a better quality inverter instead of a power line conditioner.

Also, I agree that you should focus on using 12vdc where possible at any place where no electrical service exists. Using the inverter should be done on a secondary and "as needed" basis for things like charging drills, small portable skill saws etc.

In other words the preference in terms of electrical efficiency should be to install 12 vdc lighting (Wire the entire place like an RV with a 12vdc electrical system) Use things like a portable 12vdc TV set instead of an inverter connected to a typical 120 VAC TV set.

They also make other things like 12vdc. refridgerators, microwave ovens and TV/VCR's. Look for these at any truck stop. A 12vdc car stereo CD player also makes a nice stereo system for any cottage in the woods.

I would probobly install a few solar panels to charge a few marine batteries and run everyting from that.

Alternatively, you can also charge your battery bank using your car and a set of booster cables. The alternator in your car is another good way to "charge" up your battery if you don't have solar panels.

In fact, I installed exactly what I described above
at a friends cottage without any electrical service near Bobcaygeon, Ontario a few years ago.

It's been working great since.  

73 de Charles - KC8VWM

Posts: 114

« Reply #3 on: May 02, 2007, 12:49:27 PM »

Cheap inverters produce a square wave [terrible !] , better ones a modified sine wave and the best produce a pure sine wave.

Posts: 3746

« Reply #4 on: May 03, 2007, 03:27:39 PM »


another option is to get a used Liebert full sinewave
ups on ebay or the swapfests.  Best and Eaton are other good brands to watch out for.

I've got two of them, they were used at point of sale registers in the local supermarket.

They just needed a good cleaning inside and a fresh
set of batteries.

73 james

Posts: 22

« Reply #5 on: December 19, 2010, 08:49:00 AM »

I don't even have an inverter, and still  the QRM from inverters and switching-mode DC chargers at my marina (my HF rig is aboard a sailboat) is so high that the HF band is unstable. I have a massive L/C power conditioner, but I see S20 all across the MF/HF bands. The QRM is worst around 2 MHz. Most of the noise is conveyed in through my shore power connection, but even after unplugging and stowing the shore power cable, I'm barely able to receive WWV and local AM stations.

Apparently there are no FCC noise requirements for these devices. Spark gap transmitters were banned long ago because they are "all band" transmitters. I wish the FCC would look into this source of band pollution.
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