Radio Noise from PV System

W0SD · September 2009

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

niel · September 2009

Re: Radio Noise from PV System

this sounds like all of that energy is being radiated via the pv input and you may need more drastic measures. this is dc that is coming in from the pvs and the ac is leaking up from the cc to the wires and pvs where it's being radiated. you may need to filter with coils and capacitors right at the cc and enclose it and ground the enclosure. metal conduit from the new box to the cc will help too, but watch for ground loops. all conduit being used is unlikely to stop it from radiating from the pvs so it must be stopped at the cc. the ferrites you need too many of to make the inductance you may need and can radiate in the space physically used by them before choking off so using wire for the coils that is at least as large as or larger than your leads coming from the pvs is in order to keep resistances down. the caps can be ceramic and you may need to experiment. caps on one end or the other or both. use of 2 or more caps with low and high values to cover high and low frequencies better. if need be you can make the coil of larger inductance for better filtering too and even use an iron core type to increase the inductance. that could rust outside though.

also be sure there aren't any bad or even slightly corroded connections as this sets up rectification and can make life h*ll to get rid of the birdies. this type of thing is never that easy that i have found and may not have just a single answer. keep us abreast of what you try and the results with bands affected and rough s meter readings logged by you for comparison. we don't need to know the band and s meter readings as this is for your benefit in eliminating this problem, but you can refer to it quickly for progress in some cases for our benefit too like down 2 s units on 10m and higher as an example.

as to the xw you may still see birdies, but they can just be weaker. this may or may not be a solution, but my guess is that it would improve things in general. keep in mind it can change the frequency of a birdie to land on a more used frequency by you or could be stronger on that frequency as it is difficult to predict what may come to be with just the cc switch.

Solar Guppy · September 2009

Re: Radio Noise from PV System

24khz is the primary switch frequency of the FM charge controller, it has no emi filtering so the switching noise goes straight out the inputs. FM is neither Class A or B and is well documented as a noisy controller.

The XW Mppt is Class B and is virtually silent when compared to the FlexMax chargers, also the soon to be released MorningStar Mppt controller is also Class B compliant

W0SD · September 2009

Re: Radio Noise from PV System

This is great information! I did not want to invest in another solar MPPT controller until I had some solid information. It is interesting how solar
seems to have gotten around the FCC requirements and it is rather a voluntary thing. Do you have or know of actual radio tests with the Xantrex MPPT controller?

What I have is actually a "TEST SITE" for several remote solar sites we will be installing for amateur FM repeaters so we need to get it
so we don't have RFI. Obviously the MX-80 has moved off the list for future sites unless we come up with an easy fix.

Ed W0SD

Windsun · September 2009

Re: Radio Noise from PV System

We have had some luck with ferrite filters on both sides, especially on the solar panel input.

However, for anyplace where EMI is an issue, we recommend the Xantrex XW-SCC controller.

W0SD · September 2009

Re: Radio Noise from PV System

I had a typo and I should of wrote FM80 and not FX80 for the Outback Flex 80. I am going to see what I can put together to try and do some filtering on the unit and report back. Is there someone reading this reflector that has a XW SCC MPPT 60 Amp controller who could check the level of emissions on some frequencies? With the FM80 when the controller is active I have a loud signal every 24 khz from the
broadcast band up to VHF.

My concern is that as I understand it the Class B requirements still permit a fair amount of radiation. The American Radio Relay League mentions
30 Microvolts/meter @ 30 meters so that is still quite a strong signal.

It appears the Xantrex XW SCC MPPT 60 amp and the Morningstar TS-MMP60 will be quieter since no measures have been taking with the FM80 but an actual check by someone with a XW SCC MPPT would save me spending $685.00 only to find I still have to take measures to try and reduce the interference.

Ed W0SD

john p · September 2009

Re: Radio Noise from PV System

about the only reasonable cost efective way to reduce interference is as already said use ferite rings or the 2 half types that you can cable tie around the cables near the source. If you can get large enough ones you may be able to put a few turns of the cable through the ferite rings

Vic · September 2009

Re: Radio Noise from PV System

Morning, Ed,

Posted my main reply @ OB site ...

http://www.outbackpower.com/forum/viewtopic.php?f=29&t=3735

The XW will probablly be better than doing filtering outside the CC chassis, but, still, RFI filtering is expensive, and MFGs usually target a certain spec as the limit of amount of filtering applied. Am sure that you can add external filtering to the FM which will exceed that of the XW box. I have NO experience with the XW, BUT, as you noted, Class B levels are still quite a large signal. The noises that you see are, almost certainly Line-Conducted from the CC (both on the input and output leads -- the input leads are usually much longer, and external to the power room, so are most important.

As noted in my other post, isolation of antennas from power generating areas (and to a certain extent power use areas), shielding the conductors to/from PVs (in pipe), filter in/out of CC, filter Inverter outpt, and bury/shield the AC output and so on are the most direct approaches to reducing emissions.

If it is possible to isolate your low-band antennas from the power room/PV array this should make a large difference. It is probable that the Solar has come along after you have built your antenna farm, so this isolation may not be easy or desirable -- do not know if you are off-grid, but with the number of panels noted, you are prob on-grid.

With all the shielding/filtering on the PV side, still, the low-band antennas will probably be affected by the CC emissions, due to their large capture area, and because the solar array is not shielded, and it is not really at all easy to shield them, so keeping the low-band antennas away from the PV/power room will be a large help. Also, filters usually become most effective at higher frequencies.

In my station, I realize that if I must, I can simply switch off the PV in breaker to eliminate the noise, AND, the most important low-band activitity occurrs at a point of low/no PV power input, so the CC might be sleeping anyway.

As noted elsewhere, when the CC is tamed, you will probably discover the Inverter birdies, which may need to be filtered with common-mode filters, LP filter, or perhaps, Ultra Isolation 60 Hz transformers.

Please see the post on the OB site. 73 Ed, and Good Luck, Vic K6IC

BB. · September 2009

Re: Radio Noise from PV System

From years ago (frequencies that I remember may be wrong)...

Generally, when designing computers we did not worry about anything below 30 MHz--it was assumed that any emissions would not travel far below that frequency. Also--it is very difficult to kill the lower frequencies.

Between roughly 30Mhz and 180MHz--mostly it was cabling that was the source of the emissions. The quick and dirty there was "lossy" ferrites (regular ferrite material may tend to just "ring"--high Q--and not kill common mode radiation--you want to turn the common mode stuff into heat) and shield cable (about 10' maximum was all that was required; beyond that--it did not really matter. And the distributed capacitance was enough to prevent anything from leaking out if unshielded cable was used for the rest of the distance).

Above 180 MHz--tended to be direct radiation from slot antenna... Embossed Copper foil (no insulation glue in the embossed areas for good electrical contact) tape was a easy fix for testing.

So, placing the first 10' of solar panel PV wiring in a shielded (heavy braid--used to have old navy ship braid--conduit may work--bonded back to the CC chassis) and/or ferrite protected (twisted pair if possible) run may help. No loops of wire. Run everything parallel (and twisted if possible). If there must be loops of pairs--make them figure 8 in shape.

If there is no filtering/shielding in the CC design--I am not sure what more you can do other than moving the antennas further away.

Obviously, a FCC Class B designed and tested unit is a good place to start... But, for example in the AM band--my Xantrex GT 3kW inverter still can blank out the AM radio for a few tens of feet (seems to be more of an issue with a car antenna than a ferrite rod type in my intercom--more E Field than M at those low frequencies?).

-Bill

W0SD · September 2009

Re: Radio Noise from PV System

Thank you everyone for the replies! It is most gracious of you!!! I have a lot of work and money invested in Amateur radio and a fair amount in the PV system so this is of great importance to me. I did more testing this morning and found out that the array of four 24 vdc 205 watt panels do indeed radiate as well as the wiring so putting every thing in conduit is not going to guarantee a cure. What is seems I need to do is to try and stop the 24 khz switching circuit harmonics in the FM80 box. I am looking for engineering information on how to do this. Even with a Class B rated controller like the Xantrex XW SCC I still may need to do some attenuate. Does anyone know what switching frequency the Xantrex uses?

FYI I am off grid and I can not get more antenna separation. I have a very big station with 10 towers and my antennas are already 150 feet or more away from the array except a couple are about 100 feet away. Also I do not have an inverter and if I were to get one it would be a TSW and even then I would not need it on other than if the power were off so I will not have inverter noise problems, just the solar controller noise.

I am looking for idea's and specific design information on how to get rid of the 24 khz harmonics at the FM80 box. The box is metal and seems well shielded. Very interesting to me was when I took the bottom, front cover off which is about 6 inches by 6 inches the interference did not get any worse so it sure seems the external wiring is the culprit for radiation. The harmonics get weaker as I go up in frequency but I can hear them up to 148 mhz.

It is amazing how these harmonics with a test situation I set up at 7 mhz can follow along the PV input wiring going 30 feet under ground and come out of the ground and go to the PV panel and radiate. With the panels hooked up I can hear S-8 interference on 7.0362 mhz which is loud!!! I then shut the breakers off at the panel breaker 50 feet from the controller and the noise goes completely away. I have two 24 v panels in series and two in parallel. I have the same amount of noise with just one breaker on as with both breakers on. It seems to be a combination of the input wiring and the panels at 7 mhz and above.. As some one mentioned it likely is because there is a lot more radiating surface from the PV input than the 10 foot of big twisted cable I have going to the batteries. However below 4 mhz on the 80 and 160 meter bands the harmonics are a lot stronger, like S-9+12 db on 1.832.6 mhz so at these frequencies shutting the panels off at the solar controller. let along the panels does get rid of the interference. The interesting thing is taking the front, bottom cover off the FM80 does not make it worse. It would seem it is the wiring going to the batteris which is twisted and 10 foot long but still must be radiating. Since I take the DC wiring into the house it would also be radiating I would think. I have tried my test radios hooked up to AC supplies as
well as the battery bank and have unhooked the antennas and it is coming in via the antenna.

I also note with my beam antennas that the greatest radiation is coming from the solar panels rather than looking at the Solar controller
and wiring to the panels.

I have no doubt that putting the battery wiring and the PV input wiring in conduit would help but I am convinced the noise from the panels will still do me in based on my 7 mhz testing as well as my beaming test so that is why IMHO I need to cure it at the FM80 box so I am looking for help in attenuation of the harmonics right at the FM80 box.

Again thank you so much for your help!

Ed W0SD

Dave Angelini · September 2009

Re: Radio Noise from PV System

This is real easy. If this is important to you and people have told you that the XWCC is specified for this type of radiation and susceptibility I would propose that you spend $500 and get an XWCC. You will have a spare and you can give back something here to the group. Real feed back.

PS when I tested the XWCC 2 years ago now I found a large difference in radiated compared to the MX60.

niel · September 2009

Re: Radio Noise from PV System

ed,
the fm60 is being like a transmitter with full harmonic content with the + and - leads acting as twinlead and the pvs as the actual antennas to one degree or another. only dc needs to travel the wires so filtering can and should be done. i think that filtering being left out is for cheaper production costs as most people would not have the problem you are encountering, but many fail to realize that, like your setup, this interference can not only radiate for miles, but at the lower frequencies, that bb assumed would not go far, they can radiate for thousands of miles depending on many factors. levels you describe can radiate hundreds of miles with little problem.
the prospect of filtering can be cumbersome and coils could get large. if it were me i would get the xw and further filtering efforts, if needed, then would not be as involved seeing as how some of that filtering was incorporated into the design of the xw. that would make any ferrites more effective if need be. you did not state how much reduction you achieved with the ferrites and how many were used. did you place them on both the + and - leads as both leads will radiate? did you try ceramic capacitors of .01uf or greater to ground from both leads? note that this could also be done at the pvs to ground too. did you check all connections to be good and corrosion free as this leads to the rectification problems of radiating interference? i know it's a pain and a process, but as with many hams we deal with interference all of the time with some of us tackling multiple sources, some of which are mystery sources. you do at least know what you are dealing with and it is doable to deal with it even though we don't like it. if you elect to keep the outback cc and you are willing to go through the process of addressing everything possible to be done then by all means do it. if time is of the essence or you can't go through the involved process then try the xw.

Windsun · September 2009

Re: Radio Noise from PV System

Because we have been getting more and more of these kind of reports, not only on the Outback FM series, but many other digital controllers I have stickied this thread for a while to get more comments on the subject.

As more info and proven solutions become available, I will also be updating this FAQ sheet http://www.windsun.com/General/PV-EMI.htm

It appears that currently, the ONLY solar controller that meets FCC part 15 is the Xantrex XW, and the not yet released Morningstar TS-MPPT.

BB. · September 2009

Re: Radio Noise from PV System

I know that LF travels very far... The issue is that it is assumed by the FCC and others that EMI is not very efficiently broadcast below 30 MHz. I doubt that this installation is radiating for thousands of miles.

Filtering is usually not the only issue with designing any switching circuit... There are a whole bunch of layout and timing issues with the turn/turn off of the FETs and such that cannot be "fixed" by adding on filtering.

Also, filtering DC with inductors becomes an issue too because they saturate in the DC field.

I don't know what frequency ranges you are having issues with (7 MHz was mentioned)--anyway--in the computer world that would be in the region where we would try slapping on a conducted noise filter like these DC Power Rated to 125 Amps from Corcom. It might be worth getting a couple to try on the input and output of your charge controller. They might be good for 40-50 db of reduction in the 7 MHz range...

They will probably not be cheap--but at least you can use them to see if the problem can be isolated with whatever charge controller you end up with.

-Bill

Vic · September 2009

Re: Radio Noise from PV System

Hi Ed,

Thanks for the reply and additional info.

I DO have a TriStar 60 CC, but it is a back-up unit, and have never used it. In my current steup, my Vin from the PV is 106 VDC, it will most probably tax the TS 60, as it is generally, a Pulse-Width-Modulated controller (or, alternately, a variable resistor type) controller. Am very busy now, so I will not be able to test any other CC at this moment. BUT, I am certain that the TS-60 in PWM mode will be quiter (probably much quiter) than ANY switch-mode controller. All of the major large MPPT CCs use FET transitors as switches to chop the PV in into a Pulse-Width-Modulated waveform. This approach uses a large inductor (or perhaps in some cases, a transformer) with filter capacitors as an integrator of this chopped signal. This approach needs to have very fast switching times to cut the losses to a very small value. These fast edges are very rich in harmonics, which make the emissions fairly large. The inductor/capacitor on the output reduces some of the harmonics, but there are limits. All of this is just MHO.

In addition to thi main switching of the MTTP function, there is at least one additional switcher, which provides the operating voltages for the the CC, and runs from the battery. THis switcher may also create some emissions when only the battery breaker is on, and the CC is idling (sleepein/snoozing etc).

During Bulk, the emitted signals should have fairly constant values, but during sweeps, in Asorb or in Float, you will notice the signals varying quite a bit, as the amount of current taken form the PV varies with the MPPT function.

To me, all of the noted measures will reduce the emissions, some more than others. Each will do something to help, and will sum into a fairly large benefit. Common-mode chokes using Type 31 Ferrites in a metal box, very close to the CC should help. A Low-Pass filter may be the largest single helpful item, in your situation, altho, I have not tried it. Think that if it is a Pi type filter -- capacitor on the input, an inductor plus a capacitor on the output, in a shielded box could help, and here, using low inductance caps, and perhaps a stacked-metal-film cap paralleled with lower value disc caps may be the ticket. But keep the capacitor leads SHORT, and place this LPF very closse to the CC.

Regarding the FM repeaters @ VHF/UHF, any of the filters should give a large benefit at these frequencies.

I am almost certain that the primary emissions are Line-Conducted, not directly radiated from the box. The FM60/80 should have (altho I've never seen one in the flesh) an alunimum (or perhaps zinc) casting, with a smaller steel wiring compartment, but this by itself should be perfectly adequate in shielding radiated emissions. There have been reports from others, that at remote repeater sites, CC noise has been an issue. Again, short conductors to/from the CC, sheilding of these conductors in EMT or Rigid pipe, and separation of antennas from the Power room will help. One additional item we use here: the power room is in a steel sea Cargo Container. This helps contain emissions which might be radiated by interconnections. If your remote repeater sites could use metal power rooms of some kind, and filtering on the conductors into/out of this metal room, you may benefit. Often repeaters use omni antennas, which can create problems vs directional antennas, and so on. At least for your repeater sites, you may have the benefit of starting from scratch, OR, do you ? OK, for now, gotta run. 73 GL VIc

mike95490 · September 2009

Re: Radio Noise from PV System

I would add:
a large steel PV DC Junction box, at the charge controller, built into it, would be a LC 24KHz trap filter. You have to stop the signal from sneaking back out the DC feed wires. I'd put a big honking LO-ESR cap at the PV side of the trap, and maybe the output side too. Steel box may help contain it.

Battery cables, you may have to do the same treatment, minus the Lo-ESR caps.

Hmmm... Is the OB CC a de-sulphater too ??

niel · September 2009

Re: Radio Noise from PV System

bill,
even in meeting fcc specs for radiation under 30mhz it is still possible to have that radiant energy travel long distances as hams have proven too many times using milliwatts to do it. if the said radiation is not coupled to an antenna or anything acting as an antenna like pcs then your assumption may hold some value, but not in the case of pv as the wires and pvs are radiating with great efficiency. no saturation will occur on the coil unless it is a poorly designed one with iron. air coils will not be saturated by such duality. below 30mhz is not considered just lf either, but is hf, mf, lf, and ulf. the ulf and lf area as well as the mf area will be affected more strongly as harmonics do tend to weaken as it goes up. the signal seen by him on 1.8mhz and 7mhz is strong and readings hundreds of miles away could show a signal stronger than what he sees on these frequencies.

mike,
if it were just the 24khz that was the problem then a simple 24khz trap would suffice. this is not the case as all harmonics are present through the 2 meter band meaning there is a frequency being radiated every multiple of 24khz up to around 148mhz. low pass filtering like that of power supplies is in order and after all a controller is a sophisticated power supply without the ac transformer and rectification from utility sources as our source is pv and it is a dc source that tends to vary somewhat.

boB · September 2009

Re: Radio Noise from PV System

How about some reviews by real hams, or a link to one. I'd like to hear just how good Class B is working in the real world in (< 30 MHz) HF operation for folks. Who knows ?..... Maybe it really needs to be better than that ??

boB

PS Edit: Well, Duh ! Of course I could try it too... Think I will soon as I get a chance. I need to put up my new dipole anyway.

niel · September 2009

Re: Radio Noise from PV System

too bad halfcrazy doesn't have a license yet.

nothing like a little peer pressure to speed things up.:-):D all i have is an sb50 and i never noticed any problematic radiation from it so i won't be of any help with real world observations.
output levels could be seen on scopes as well and maybe sg can chime in with a summary of that info for you and possibly a comparison between the 2 controllers if he has one of them. that reading would represent the worst case condition with all of the energy being radiated even though mismatched impedances and other losses would usually cause some loss of radiated power. it doesn't sound like it's losing much power in ed's case.

W0SD · September 2009

Re: Radio Noise from PV System

TEST RESULTS

I have no problem spending $600 for an Xantrex XW SCC or upcoming Morningstar "IF" it will cure the problem? I am hoping someone out there has a Xantrex XW SCC and we could run some tests. Dave Sparks say 2 years ago on the test he ran it was much better than a Outbacker so that is motivation that it will help? Dave can you please give me more information? What frequency or frequencies did you run the test. What was the strength of the signal on the Xantrex.

The question on getting the Xantrex seems to me boils down to how much better? It probably is worth the $600 even if I still have problems. For one thing if it would cure things from say 7 Mhz and up and it well may not below 7 mhz but for me those are night time bands so the controller would be asleep. If this would be the case I would do it instantly. Also anything I would do additionally should improve things faster than now where I am starting at such a high level of signal strength.

FYI this afternoon I tried .22 capacitors to ground on the PV input leads and a .22 capacitor between the two leads and reduced the level from S-9+15 db to S-8 on the highest peaks. As I said earlier I have been seeing three levels of strength on 1.8321. At the highest one that would be some where around 20 db less. At the lowest of the 3 levels it is S-8 with no capacitors and with capacitors is it aout S-5 so that is also a good and similar improvement. Obviously the S-meter is not a lab instrument.

I am going to try the capacitors in the 7 mhz range tomorrow. I would also like to try some inductance. I did some reading that for an inductor to be effective it should have an iron core. One suggestion is a tight wound coil about the size of a paint spray can about 6 inches long and to fill it with iron rods insulated from each other. My wire is about the size of my little finger. The coil is then bypassed at each end with .1 to ground and .1 between the wires at each each end. I could start out with the PV input wires as that seems to be the big radiator. For the battery leads it would be easier to put them in conduit and by pass with capacitors at the battery end.

If I can get rid of it at 7 mhz or above I can easily work around the interference below 7 mhz by shutting the panels off it I want to operate below 7 mhz in the day time. I could live with it if it got rid of it at 20 meters and up.

I am not an engineer so any suggestions are welcome about the "filtering" design. The FM80 appears to have a pretty good size electolytic by the input/outuput terminals but I have no diagram.

Ed W0SD

niel · September 2009

Re: Radio Noise from PV System

try adding even more capacitance and use the ferrites too and see what happens. come to think of it, were the ferrites still inline when you added the caps or not as you didn't say? why did you not just go to the 40 meter band and see what your caps did as it is a matter of just going up the dial?

W0SD · September 2009

Re: Radio Noise from PV System

Ferrite Cores

I re-read all the post several times and will do so again. Questions were asked about ferrite. FYI I have tried 4 clip on ferrite cords on each PV input wire for a total of eight that just fit over my wire. They do absolutely nothng!!! I have tried them all on the battery wires and absolutely nothing and I have used them on both the PV input and the battery leads. I have moved them from as close as possible to the controller to farther away. The clip ones were gotten from Northern Sun and WInd and should be the correct material.

Ed W0SD.

niel · September 2009

Re: Radio Noise from PV System

is there enough room inside of the ferrites to loop more turns through it? if not then leave the ferrites there and just concentrate on adding more capacitance as that has shown a result.

W0SD · September 2009

Re: Radio Noise from PV System

I should of went to 40 meters, dumb mistake on my part, but I was fixated on getting a valid test on 160M. I wrote down the interference levels and then it took me awhile to put in the capacitors. I was fixated on tearing the capacitors out quickly and seeing if the interference was back to what is was originally to validate my test which they were. Knowing what I know now the levels seem to be very, very constant but at that time I was not sure.

I did not try the ferrite clip ons at the same time as they did absolutely nothing by themselves but it sure would be worth a try.

The sun is going away so I will try again tomorrow if I have good sun and constant values.

Ed W0SD

Vic · September 2009

Re: Radio Noise from PV System

Hi Ed,

interesting test results ... about 20 Db reduction in noise signal is not bad for your first try.

RE inductors, you probably do not need a lot of L. If you had some powdered Iron cores (often painted red) this would porbably be OK. The most common Ferrites by far are type 43. This is a VHF material, and not very useful in the HF range. Type 31 ferrite material would probably be your best bet, but is is not common at all, and furthermore, there are almost never any marking on ferrite cores or clamp-ons, so it it difficult to determine the material with the eye.

Perhaps, as an experiment, you could try 20 or 30 turns of #10 solid (if possible solid) wire around a 1.5-inch PVC pipe or something, with capacitors at each end, this might be in the range of something useful. Solid wire is just a bit easier to work with, as it tends to stay put. You may find better rusults, later, if the inductors were divided into two sections, with capacitors at the center point of the coils. Use an inductor/capacitor set in the Pos and Neg leads of the CC It is possible that the noise currents in the capacitors might trip GFIs in some systems, but you probably do not have them. As your filter becomes more effective, you would need to pay more attention to coupling between the input and output of the filter, perhaps using a shield near the center.

As you know, each additional Db of attenuation of the noise tends to come at an ever-increasing cost -- diminishing returns.

Off to a meeting. Good Luck, please let us know how you do. Vic

mike95490 · September 2009

Re: Radio Noise from PV System

I doubt ferrite will work, as it will saturate fairly easily. I'm thinking some air core enamel windings, and low ESR caps. If you don't use Low ESR caps, you aren't going to see much effect. You have to stop the radiation from the long panel wires, right at the charge controller. Aim for Vmax of your panels +20%, that should be safe enough. What's the Array voltage again?

Windsun · September 2009

Re: Radio Noise from PV System

I am somewhat surprised that the ferrites did nothing, as some of the testing I have done on other things, such as fluorescent lights showed a pretty good decrease in most cases. But there I only had two wires to worry about.

I suspect that the majority of the radiation is coming from the wiring to the panels, but it is also possible that some is coming from the battery temp sensor (have seen that on a Xantrex C-40). On testing that I did long ago, the controller to battery wiring was a fairly minor source - the batteries seem to swamp out a lot of it. But that was an older system, with a direct ground from the battery negative to a nearby earth ground post, which may have been part of the reason.

tallgirl · September 2009

Re: Radio Noise from PV System

Windsun wrote: »

I am somewhat surprised that the ferrites did nothing, as some of the testing I have done on other things, such as fluorescent lights showed a pretty good decrease in most cases. But there I only had two wires to worry about.

I suspect that the majority of the radiation is coming from the wiring to the panels, but it is also possible that some is coming from the battery temp sensor (have seen that on a Xantrex C-40). On testing that I did long ago, the controller to battery wiring was a fairly minor source - the batteries seem to swamp out a lot of it. But that was an older system, with a direct ground from the battery negative to a nearby earth ground post, which may have been part of the reason.

The ferrites aren't going to do anything because dI/dt is phat and anything that can be put around the PV conductors isn't going to be able to store enough energy in the magnetic field (see "saturated") to help.

niel · September 2009

Re: Radio Noise from PV System

guess everybody is against the ferrites, but you could still wind some air coils to try.

tallgirl · September 2009

Re: Radio Noise from PV System

niel wrote: »

guess everybody is against the ferrites, but you could still wind some air coils to try.

Someone suggested winding around an iron core. I'm not against inductors, I'm just against pointless ones.

boB · September 2009

Re: Radio Noise from PV System

For common mode filtering, high permeability ferrite will normally be THE way to go.
That is, all wires (or both + and - PV wires) going through one toroid or clamp on.

Ferrite will normally saturate if placed on one individual current carrying conductor (differential mode), but may help at lower currents.

There is still a bit of an art to getting this all correct though..... And also some trial and error plus a wee bit of black magic.

boB

Radio Noise from PV System

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