Radio Noise from PV System

boB · July 2012

Re: Radio Noise from PV System

It will be interesting to see what Outback has to say about this.

inetdog · July 2012

Re: Radio Noise from PV System

W0SD wrote: »

I am disappointed by not surprised that I have RFI noise on amateur radio. I find a "birdie" about every 24 khz on all the amateur bands. I am using an Outback Flex 80. If I shut the breaker off to the four 205 watt 24 volt panels the "birdies" go away other than on 80 meters
I can still barely hear them and if I shut the Flex 80 off then they go away. When the controller goes to "sleep" I of course do not have them.

I have twisted the wires out of the controller going to the battery and I have tried ferrite all to no avail. I did some "sniffing" with my HT on two
meters and I find the lines with about 50-60 volts coming in from the panel are radiating as well as those going to the battery bank. It would
not be real hard to put the wires going to the battery bank in conduit but I wonder if anyone has had success doing this. I would assume you would have to bypass each end of the conduit to ground? It would be a lot more difficult to put the wire coming in from the panels in conduit. I have the first 25 feet buried.

It is coming in over the antenna's as I can use antenna's farther away and the "birdies" are weaker and I can point my beans away and they
get weaker.

Another question? I note that the Xantrex MPPT controller has an FCC Class B rating. Is there anyone here that has this unit and could tune the ham bands and tell me if they have "birdies" They are very loud and are, not problem to hear from the Flex 80.

Ed W0SD

If you are seeing a birdie about every 24 KHz, it is an indication that it is related to a 24 KHz switching frequency in the DC to DC convertor of MPPT or the current regulation of PWM, with a very sharp edge that is generating lots of high harmonics.
Some additional filtering inside the CC would be the best attack, but not really feasible without cooperation from the inverter or CC manufacturer. It is always easier to eliminate/reduce the source of the interference than to try to filter it out later. There is a tradeoff between a fast switching waveform to minimize losses in the switching element and a slower switching waveform to minimize harmonics.

niel · July 2012

Re: Radio Noise from PV System

this is interesting as to what this installer is saying, but i think he over thought it or he may have been misinformed. now longer wires will also increase inductance and nobody puts up warnings about not having wires too long due to the fets not switching properly. overcoming the resistive losses is a factor in long wire runs though. the inductance that is added is to affect frequencies far beyond what the desired frequency is (0hz) and the power content of those harmonics are much lower, especially in the rf spectrum range of things, so it will not have an adverse effect to the controller imo. we are NOT talking of very large amounts of inductance in the suppressing emi/rfi.

inetdog · July 2012

Re: Radio Noise from PV System

niel wrote: »

the inductance that is added is to affect frequencies far beyond what the desired frequency is (0hz) and the power content of those harmonics are much lower, especially in the rf spectrum range of things, so it will not have an adverse effect to the controller imo. we are NOT talking of very large amounts of inductance in the suppressing emi/rfi.

Right, and since the goal is to stop harmonics from leaving the box at all, two measures to accomplish this would be:

1. Use a co-axial capacitor (available for filtering automotive alternator noise) on both leads on the DC side, and
2. A combination of a parallel capacitor to ground and a series inductor on AC leads. The inductor should be closest to the wire exiting the case and the capacitor should to from the outside end of the inductor to the neutral (not to the case ground.)

Either of these should not be done except by a qualified electrician. A ferrite (with both hot and neutral or both + and - leads wound in the same direction though the same ferrite toroid if possible) is the only remedy which does not involve making a direct connection to any wires and is therefore DIY-safe.

niel · July 2012

Re: Radio Noise from PV System

a cap is one possibility and i agree some may lack the skills to wire up this simple part.

as to adding the inductance, this is quite easy to do for any diy person. they don't have to use the donut types as any of these would suffice too,
http://www.solar-electric.com/nosufefi.html
also, it is possible to wind a coil out of insulated wire that would also add some inductance and this could be some of the wire already inline going to or from the cc. the thicker the wire the more difficult it may be to wind a tight coil, but larger coils can still add a tad of inductance. there's no law saying you can't run the + and - together in the same ferrite core either, be it a donut or otherwise, and if one can fit more turns of the wires to loop back through the ferrite material then they will gain even more inductance. in the case of just a couple of turns of wire and no ferrite material involved then the inductance produced by this will likely be too small to be effective at radio frequencies.

54d18 · September 2013

Re: Radio Noise from PV System

I had pretty much the same issue with my Rogue MPPT,
I added ferrites to the solar leads, but still no success, I then added
a small, maybe 100 pF Ceramic Cap accross the solar leads and that
pretty much did it.

Lots of trial and error in my opinion.

T

NorthGuy · September 2013

Re: Radio Noise from PV System

54d18 wrote: »

I then added
a small, maybe 100 pF Ceramic Cap accross the solar leads and that
pretty much did it.

Cables usually have capacitance of about 15pF/foot. They're sometimes long. 50ft cable in my system gives me 750 pF.

An that's, of course, not counting 100 mF of the controller's input capacitor

niel · September 2013

Re: Radio Noise from PV System

54d18,
when you placed the cap was the ferrite still in place? if so what do you observe when taking it out of line?

niel · September 2013

Re: Radio Noise from PV System

north guy,
the trouble with that wire capacitance is that it takes a long length of wire to achieve that desired capacitance and the capacitance does vary from wire to wire. the inductance and capacitance sets up a resonant point for what is basically now an antenna that is good for radiating the interference. now a capacitor can just change the resonant point and still be an antenna, but it may be in an area making the radiated energy you observed smaller as more is being attenuated. electrolytics do not always function well into the rf ranges so don't count on them for this purpose.

54d18 · September 2013

Re: Radio Noise from PV System

Niel, the ferrites were and are still in place, when the
noise dissappeared on the radio, I pretty much stopped.

T

niel · September 2013

Re: Radio Noise from PV System

remove any ferrites if it is easy to do and see if the noise increases. my point would be that it isn't just the cap working.

Scuba-Junky · September 2013

Re: Radio Noise from PV System

Which controller model? What end of the solar leads did you put the cap? Solar end or cc end of cable? Are you a ham radio op and if so, did this clean things up for the HF bands? What voltage is your panel array? What voltage is your battery system? I'm starting to think that all of these factors play into the equation.

Vic · September 2013

Re: Radio Noise from PV System

Scuba-Junky wrote: »

Which controller model? What end of the solar leads did you put the cap? Solar end or cc end of cable? Are you a ham radio op and if so, did this clean things up for the HF bands? What voltage is your panel array? What voltage is your battery system? I'm starting to think that all of these factors play into the equation.

Hi SJ,

Normally the first place to put emission reduction components is as close to the source of the emission generator as possible. In the case of an MPPT CC, this would be across the PV input terminals first. Lumped, rather than distributed capacitance if often the best. At times, placing ferrites and perhaps capacitor/s at the output terminals of the CC can help. Running power conductors in well-grounded, TIGHT metal pipe helps a lot.

Believe that for the Classic CC to meet FCC B, the only addition that was required, from the initial design, was the addition a small amount of C at the PV input terminals. But, FCC Class B for devices like CCs applies only to frequencies at/above 30 Mhz. For HF enthusiasts, this leaves all frequencies of interest untested for emissions.

Still, the best single remedy for RFI/EMI seems to be the separation of antennas from the Power Electronics, PV array/s, and unshielded power conductors, in my experience.

FWIW, YMMV, Vic

KD0CAC · September 2018

New to site , not new to alternative energy , my last system the batteries lasted 12 1/2 yrs. - 4 Trojan L16's .
I am also a ham radio guy , a little surprised that no posts since 2009 .
But on the other hand , with everything coming from china [ too many lack of quality from there ] gear .
I suspect the issue will only get worse .
I use to have subscription to Home Power for a few decades , and the RFI - Radio Frequency Interference was not covered much .

John

Vic · September 2018

John said, " ... But on the other hand , with everything coming from china [ too many lack of quality from there ] gear .
I suspect the issue will only get worse ... ".

Welcome to the Forum. Yes, the previous post was dated Sept. 2013.

Of course, NOT everything comes from China -- MidNite products are made in Washington state, USA.

Also, regarding noise from MPPT Charge Controllers (CC), Emission regulations from the FCC, begin for frequencies of 30.00 MHz and above. The entire HF spectrum Emissions regulations apply to Line Conducted Emissions from about 150 KHz to 30.0 MHz and only for electronic devices that connect to the AC power mains. These HF emissions are much stronger than those that are radiated, above 30 MHz.

As has been noted in this discussion, there are a number of effective Emission reduction techniques for CC emissions, and similar solutions that apply to inverters and other switching devices -- on our properties. Emissions from close neighbors, not so much.

IMO, 73 GL, Vic

Estragon · September 2018

One of my summer projects has been to install led lighting which runs directly off 12Vdc. I'm using wireless dimmer switches for most, and have what I suspect is an RF problem.
The dimmer:

http://www.leevalley.com/en/hardware/page.aspx?p=70325&cat=3,70322,75514&ap=1

The switches use 433.92Mhz. One has a both transmitter and receiver in use for control, two are controller by the receiver only so far. The problem is the lights are coming on (or sometimes going off) by themselves. It's happened on all the wireless switches, so I'm inclined to rule out defective dimmers or wiring faults. They appear to use the same frequency but different codes.

My assumption is something is creating RFi at that frequency and somehow randomly sending something resembling the code for a particular switch receiver.

This has been happening mostly late at night when charge controllers (3 MN Classics and 2 MS Tristar PWM) are resting. It's happened once when I had the MS 300w 12v inverter turned off. It's happened with the Outback 3500w 48v both fully on, and in search mode (though it may have happened when the OB woke for an AC fridge cycle). Would this suggest the OB inverters are the source?

The gear is in an enclosed crawlspace under the space with the lights, so I'm considering some sort of shielding on the underside of floor joists. Any thoughts on what sort of shielding is likely to be effective?

I'm also wondering if it could radiating from AC wiring (in which case, shielding the gear area won't do much good). The 12Vdc powering the lights is a separate system than the 48V inverter (not tapped or converted), so I'm assuming it wouldn't be DC wiring.

Vic · September 2018

Estragon,

It is possible that RFI could be causing this issue.

But, somehow, I kinna doubt it. Do wonder if some other device in your area is using the same 433.XX MHz frequency for remote control -- Keyless Entry, UHF TV/Satellite RX Remote, RADAR, etc.
433.XX MHz is used for auto Keyless Entry systems for cars built for the non-NA market. All of the remote control devices use very low power, but the receivers in controlled devices are usually quite crude.

433-ish MHz is in or near an ISM band, IIRC. There could be some such device near your location that might be running more output power than a typical remote transmitter ... :
https://en.wikipedia.org/wiki/ISM_band

RFI from Power Electronics should have its Emissions well attenuated, at your remote light's frequency.

No time now to spend on this, but isolating the components of your system might help you get a better idea of what is happening ..

More later, Vic

Estragon · September 2018

Thanks Vic, interesting info.

No doubt the receivers are quite crude. I had a dud one (worked standalone using the rotary dimmer when I installed it, didn't the next day) so I opened up to see if it was just a loose wire. It's just a little board with a coil antenna, rotary dimmer, and physical interface to 12v in/out.

I'm over a mile from the nearest (human) neighbour, so anything external would have to be relatively high powered (or not human, like maybe an RF tracked critter).

I do have keyless fobs for cars though (Audis). The cars are miles away, but the fobs are at the cabin, and have coin batteries. Is it possible they transmit periodically at that frequency in a way that causes a state change in the lighting receivers? To test the theory, maybe I could put the fobs in a shielded location (like a metal box)?

Estragon · September 2018

Update: Found a wireless thermometer that appears to be using the same frequency. Took the batteries out of the remote transmitter as the lights going on and off was driving me crazy. So far, no more ghosts

Vic · September 2018

Thanks Estragon for the update. Knock, knock ... hope that you have found the culprit in that thermometer.

Good luck, and please let us know how things are going. Thanks, Vic

garynappi · October 2019

I'm not a ham but I spent a lot of time in an EMC lab doing EMI/RFI, radiated / and conducted testing on PC's.

If you have any fluorescent tubes replace them with direct replacement LED types, they may help. "Dirty" DC from switchers can also be corrected with passive (not torroidal) filters, but if there is ripple in the DC, filters will raise the DC voltage.

Radiated cable noise may be corrected with metal conduit but it not only needs grounding on both sides, but whatever it goes into or comes from must have grounded shielding inside it or you waste your time. Adhesive backed copper tape or conductive paint inside control box cavities help that end. Air vents also allow noise leaks and a grounded wire mesh in or over them closes that hole.

Many AC power cords with factory installed torroids are available also.

Regarding torroids and other cable wrapping, one may not be enough, and more than one with different freq suppression characteristics may be needed on the suspected radiator, or they may not help at all. Clamp on types may be a quick fix but don't overlook wrap core types.

Bob said it right... noise suppression is a bit of black magic, and curing it may be a PITA.

Solar2 · October 2019

Interesting thread.
I am a ham and spend most of my time on 160, 80 and 40 meters.
We also are full solar with two XW Zantrex XW-6048 inverters and five XW-MPPT60-150 charge controllers.
The ham shack and solar equipment are in the same room about ten ft apart.
The solar panels are on the roof and I have wire antennas above the panels.
For a pix go to QRZ(dot)com es put my call AG7BN in the search.
Obviously we had big RFI problem.
The inverters when output is less that 2 Kw are mostly quiet.
But the charge controllers are very bad.
If I were to do it again I would not use MPPT type charge controllers for several reasons.

But we took a somewhat different approach to the RFI problem.
First, all wiring including the wiring to the solar panels is in metal conduit.
But the main effort was to get the antenna away from the solar equipment.
The wires over the panels are worthless antennas in the day time having S9 + noise.
I put a loop antenna some 500 ft away and about 160 ft up from the solar.
The feed line is 1 5/8" solid shielded outer conductor coax buried to the top of the mountain.
A loop is primarily horizontal polarized.
For some reason noise seems to be mostly vertical polarized.

The result is a S1 or less noise level most times.
We are located away from power lines and population.

Marc Kurth · April 2022

I was reading this old thread and discovered that QRZ lists AG7BN as Silent Key as of early last year.

Vic · April 2022

Hi Marc,

Thank you for noting the passing of "Ken", AG7BN. Had exchanged several e-mails with him, but never did "work" him on the radio.

Very sorry to hear this news, he had a very interesting background and life, and will certainly be missed.

You may well be a Ham, ... presuming too much. (73), take care, Vic

jkharvie · May 2022

Regarding AG7BN...RIP, https://naara.org/?page_id=127, (73) N3JKE

PS. I am new to realizing solar, with 27 Enphase IQ 7+ microconverters, + associated 400 Watt panels mounted on roof. Now in 6th day of operation...

garynappi · March 12

OP, you did not say where your controller is mounted but if it's in some sort of enclosure, painting the inside of the cabinet with conductive paint or lining it with copper tape and grounding it is a big hammer solution (albeit more expensive than desired) to think on.

Failing that before 86'ing the CC or relegating it to a spare I'd take it apart and do the big hammer approach on the CC cabinet if it's not already there.

Radio Noise from PV System

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