Radio interference

Glamsland

Hello!
Norway calling....

I have a problem with radio interference on the FM band 80 to 108 mhz .(typicly norwegian radio).
Its the same interference if i use battery radio or the 220volt radio.

I have aepsolar tracer mppt 30amp CC, and a "unknown" brand inverter 500w (300$ type).

All the electronics are mounted in a small building 15 meters from my cabin. There is a thich burried cable going from the inverter to the cabin.
How do i seek for the main problem? I am sure you guys know "the right way" , many of you have been there, done that...??
I have tryed to search on the forum, but it is so widely explaned , an so many solutions.
Anyone who can help me to clean op the FM band?

Runar

norway

feedhorn

Re: Radio interference

Just a process of elimination...


Good thing you got an FM instead of an AM problem. FM is easier to fix.

First find out if its the inverter or charge controller that is causing the problem. Turn the off individually and see where the noise goes away.

Next get a 0.1uf 400 volt capacitor and put it across the input then the output of the offending device and listen for an effect.

If the added capacitor doesn't fix the problem you may need to find a better inverter or charger.

An AC noise filter component may work better than just an added capacitor.

Especially, pay attention to the noise that may be getting into the solar array because it acts like a large antenna.

You may need to add a 0.1 cap to each panel.

BB.

Re: Radio interference

Does the problem go away if you disconnect the solar charger (and/or at night) or if you turn off the AC inverter? Trying to figure out if it is the charge controller or the AC inverter.

Ferrite beads clamped around both/all wires from a cable can help (placing all wires through cable is especially important for DC/battery cables--The constant DC current will "saturate" a ferrite bead if clamped just on one + or - lead at a time).

Radio interference is very common with solar/battery power system--The MPPT controllers and inverters/battery chargers are naturally noisy devices. Although, the problem is not usually FM as often (FM is much more resistant to RF noise).

Also, if you have the option, moving an external antenna away from the equipment shed/solar panels can help.

If you have any HAM radio (amateur radio) operators/clubs in the area--Try contacting one of them--They can be very helpful and appreciative of you trying to quiet down your system. It could be very helpful for HAM folks in the area.

-Bill

waynefromnscanada

Re: Radio interference

My MX-60 controller was horribly noisy, even on FM. The new MidNight Classic however is happily, more or less RF silent.

BB.

Re: Radio interference

Here is a Ferrite company (for basic information):

http://www.fair-rite.com/newfair/index.htm

-Bill

Glamsland

Re: Radio interference

Thanks for many good ansvers! I will test if its the cc or the inverter next weekend when im going up to the cabin.
About ferrite beads, are they ment to be clamped all the way , the hole length of the charger/battery cable frem the cc? I have 1meter cable from cc to batteries.and about the ext antenna on the radio, i will try that, it have a external ant plug ..

Runar

Vic

Re: Radio interference

Hi Runar,

As BB Bill mentioned, often the most effective solution is to separate the antenna from the/any noise generator. If most or all of the FM stations that you are interested in receiving are in one general direction, a Directional FM antenna should help very much, although the FM receiver would need an external antenna connection. On FM radios, it is very common for them to have such an external antenna connection.

Regarding trying to reduce the noise coming from the Charge Controller (CC) or the inverter, as was also noted, turning off the PV input and the output (both of them) for the CC will help you tell weather it is the main problem. If the noise is not reduced or eliminated when switching off both the input and the output of the CC, them, next try switching off the inverter, and use the battery radio to look for a noise reduction.

If you have a battery operated portable radio, you can move it around the cables connecting to the CC, and the inverter, when listening on the FM band. The largest noise source should create the loudest signal in the FM radio, when it is moved around, and very close to these cables.

For the FM band, using a capacitor may be the easiest and perhaps an effective approach in reducing any noise.

For the CC perhaps a fairly small value of capacitance would be required for noise on the FM radio band ... possibly in the order of 0.01 microfarads -- 0.01 uF. Possibly even a smaller value than that. Keep the wires on that capacitor as short in length as possible. A Disc Ceramic capacitor should have good suppression ability at the VHF frequencies of the FM band. The CC PV input terminals are the most likely to be creating the largest amount of noise, so try these terminals, very close to the CC, first.

Ferrite chokes, with both the + & -- leads of the PV input to the CC can be very effective. The larger the number of turns that you can wind through the core, generally the better for noise reduction. If this does not completely eliminate the noise, try a similar core, with both wires wound through the core again, on the output cables on the CC. For either the capacitor or the ferrite cores, keeping them very close to the CC will help them be effective.

Also, twisting the cables from the PV to the input of the CC, and possibly on the output cables of the CC to the battery, within the first few meters of the CC, can also help.

The most important thing to try first, however, is separation of the FM antenna for the radio from the PV array, and your power room. And then perhaps a directional FM antenna, if the FM stations are generally in a single direction. And then, of course, locate this antenna so that it will be pointed AWAY from the PV array and your power room and cabin.

Good Luck, please report back on your results. Good Luck, Vic

niel

Re: Radio interference

it may be unclear to you, but the capacitor and/or ferrite beads need to be placed as close to the offending device as is possible to be more effective. if it is the controller then determine if it is the pv input throwing out the noise or if it's on the battery side or both. the portable radio placed near those wires will indicate if they are throwing off rf noise. similarly for the inverter as you should see if the portable radio picks up the noise on the dc side of things and/or the ac side of things. often times a better inverter or controller can help to eliminate the noise, but there's no guarantee of this. i trust you don't have one of those battery desulfator devices there as they are crap and could cause the noise and sometimes they could interfere with other electronics from operating properly.