RF quiet inverters
Getting my 520 watts of solar online and my Samlex inverter totally wipes out HF with S7 plus noise. Any low cost inverters that are quiet RFI wise? A quiet fan would be a plus also, mine sounds like a 747 spooling up for takeoff. Current model is the SSW1000-12.
I've been into alternative energy for over 30 yrs. , but ham radio for about 4-5 yrs. and have been waiting to see good , tested responses to this question .
My solar system has not been up & running since I've been a ham , batteries reached there life cycle and have had regular grid service , so have not had a chance to check out some of the quality inverters .
But if you are only going to look at low end inverters , then I would think you would have to keep the cheapo inverter at a long distance from you shack , and maybe give the inverter room the tin-foyle hat treatment and add filters .
Another option and more efficient is most ham radios run off 12v , so turn off the inverter , use a battery-booster [ they sacrifice some current to maintain high voltage ] , there are losses each time you manipulate power [ inverter ] .
Then without have the numbers , your power consumption , its possible that you could run off the panels going to the batteries , most panels run about 17v for charging and keep the batteries in circuit to make up for surges + & - , you may want to add something to the rig supply to limit voltage to about 13.8v .
Last edited by KD0CAC; 07-09-2012 at 12:30 PM.
Inverter runs the computer for logging, the power for the antenna switch, and other misc stuff. Outback has good RFI ratings but at $2k that isn't on the list right now. The PST series from Samlex are supposed to be quiet and I may test one.
Line filters might solve/reduce the noise problem.
Digikey, Curtis Industries, FD00DD100, 80 VDC, 100 A, $83
Digikey, Curtis Industries, F1199DD20, 250 VAC, 20 A, $20
The cases of the filters should be attached to the inverter chassis. There is a possibility that the inverter will become unstable with the filter between it and the battery. If so, an RC damping circuit needs to be added at the filter output. It should consist of a 0.1 ohm resistor in series with a blocking capacitor of several thousand uF. I can give you part numbers for this.
Last edited by WX7G; 07-10-2012 at 04:57 PM.
For a cap at the DC filter/inverter point the CDE , 12,000 uF, 25 V, screw terminal, $27 looks good.
Already put bypass networks and ferrites on the. Power leads internally. It had nothing from the factory. Using a ferrite on the ac sde also with no help. Design looks pretty cheesy from what I have traced out, haven't been able to locate a schematic. Thing is a very effective rf generator!
I have a Xantrex Prowatt SW 1000, it is a sine wave inverter and seems to be a lot better than any of the modified sine wave inverters I've used.
Mine runs a service monitor on the road. I use it to monitor the 450 band out and about, I haven't really used it for any ham purposes except for at the house and other places where I have commercial power. I will have to try it some time and see what happens when I get down on the HF bands.
Proper EMI filter will fix the problem. I don't know what you installed or how it was installed.
On the DC input side the 12 volt to 170 volt switching power supply is a good noise generator. On the AC output side the class-D sinewave generator is also a good noise generator.
WX7G, NARTE Certified EMC Engineer
I challenge the line filter idea.
For some 3 years, K5HAB and I, pulled every trick in the book to "fix" the RFI issues with a Xantrex 2,500 watt, MSW inverter in his Renegade RV. The head engineer at Xantrex was consulted many times. After repeated requests for help, they eventually came up with an input filter (consisting FT240 core, and two capacitors) which didn't help one iota. A Tripplite filter reduced the output RFI by a couple of dB, but the RFI level on 20 meter nearly pegged the meter.
The real culprit was the RFI from the wiring on the DC side of the inverter. Considering the current draw is upwards of 200 amps, there isn't much that can be done in the way of filtering. Shielding the incoming leads from the battery bank, actually increased the RFI level. Finally, the whole unit was replaced with a Precision MSW inverter, and the RFI level dropped to about S1 or so.
The whole experience taught me one thing. If the company is recalcitrant in providing technical help, as Xantrex was, it is time to move on to someone who will!
Most power supply design engineers know little about EMI. Fortunately I know both and do both for a living. I design high power EMI filters for military products.