Radio Noise from PV System

[W0SD]

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]

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]

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]

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]

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]

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]

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]

Morning, Ed,

Posted my main reply @ OB site ...

http://www.outbackpower.com/forum/vi...hp?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.]

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]

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