RFI Noise??

Re: RFI Noise??

BB. wrote: »

Yes, the + and - cables should go through together (and wrap together, if room). Larger DC current with "saturate" the iron/ferrite core and make, essentially, non-magnetic in terms of killing your RFI.

When you pick a ferrite--you need to look at the material itself and make sure it is "active" in the frequency range of interest.

-Bill

One small addition to that one: Putting both + and - through the same ferrite will cut back the "common mode" interference which is equal in amplitude and phase on both + and - outputs. But if the - lead is grounded, all that the ferrite will do is make the same amount of RF current flow in both the + and - wires.
If you can work out a situation with a reduced number of turns which can avoid saturation of the ferrite (the same ferrite which is good for 20 Amps AC should also be able to handle 20 Amps DC) then you should also put a second ferrite on the ungrounded (if there is one) lead only. Luckily this will only have to handle the panel current and not the battery output current.


Probably the best solution available to you on the battery side is to keep the wires to the battery as short and large as possible and twisted, and perhaps put a capacitor (of the appropriate voltage and sized for the frequency range of interest) from + to - just on the battery side of a single ferrite. At lower frequencies the chances of radiation on the battery side are low but at 156 MHz, you could be getting significant radiated noise unless the wires are only a few inches long. The batteries should act as a capacitor to keep interference from passing out the other side on the load wiring, but they may do nothing to reduce radiated RF from the connecting wires. Keep them short and twisted and maybe even put a shield around them.

I would not worry about radiation from the panel wires, as long as you can keep the noise generated by the CC from reaching them in the first place. Shielding them on the way to the panel will not help with radiation from the panel elements themselves.

And finally, if you have an amateur radio friend, ask him about designing a "trap" specific to the 156.8 MHz frequency you are having the most problems with. It can be a simple as single properly cut piece (exactly 1/4 wavelength at 156.8Hz) of coaxial cable with the end left open and properly weather-sealed.

Re: RFI Noise??

There is this exhaustive (or perhaps exhausting?) Thread:
http://forum.solar-electric.com/showthread.php?5887-Radio-Noise-from-PV-System

Second, if the main radio that you are using is a base station type set, you could try removing the antenna coax at the radio, open the Sqelch, and note if the noise is; reduced, gone, or about the same. This will reveal weather the interference is Radiated, or Conducted noise. If radiated, it might be possible to move the antenna, altho, if on a boat, the common vertical antenna it is probable that the antenna cannot be moved far enough away from the electronics and wiring to make a difference.

And, guess that you KNOW that the interference you are sleuthing, is actually coming from the CC (?). Obviously, switching off the input and output breakers should tell this story ... know that you know this.

Sometimes, conducted noise can enter the radio itself (if it is a base station radio) via the power leads, so in this case you might try filtering the power leads to the radio, where these leads connect to the power supply, or battery.

For either conducted or radiated, Common-Mode Chokes, and shielding of conductors should help. As noted, a small disc ceramic capacitor across the PV In terminals and another of ht Battery terminals right at the CC could help. In the case of the PV in capacitor, make certain that the capacitro can tolerate the max possible PV voltage. Vic

Re: RFI Noise??

Yes, niel,

I had NO confusion what YOU were saying, YES, HTs and Hand-held RXes are great tools, as are portable AM batt operated radios -- great sniffers.

In my limited experience, PV cables are the dominant RFI source, as, traditionally, these leads are the longest and generally most exposed. Batteries are low Z, and leads generally short, but at VHF, of course, the batts are not teriffic capacitors.

YMMV, Good Luck, Vic

Re: RFI Noise??

"Someone here mentioned or questioned if the interferance was worse when the
unit was at a lower solar input, and the answer is yes, when the unit is at max output,
there seems to be less interferance."

that's odd as i would've expected it to be less at lower solar input or am i reading you wrongly? anyway, read the other thread on the mx60 noise and that should help some. do know you may or may not cure it. also, it may not hurt to get a hold of marc at rogue and see if he can be of assistance too.

Re: RFI Noise??

A quick check online and your controller appears to be a MPPT type. I'm using a couple of ProStar 30M controllers, which are PWM. These too produce some RF interference. I tried to capture the video with a low resolution video camera, but it did a poor job of showing the noise on the computer screen of one of my security cameras. I used a ferrite to greatly reduce the noise. Initially, I used a split ferrite to test the fix first. It actually caused the two pieces to buzz in my hand, making a lot of audible noise.

[video=youtube_share;ffXBcXPQ9gc]http://youtu.be/ffXBcXPQ9gc[/video]

I later installed a one piece ferrite on both the positive and negative cables as close to the controller as possible. This didn't fix the issue 100%, but the result was satisfactory.



Good luck with your gremlin. Please post any results, good or bad.

Re: RFI Noise??

niel wrote: »

robert,
i never gave it a thought that you may hear the 2 separate halves vibrate audibly, but as the pwm cc is typically functioning in the audio frequency range it can very well do this and you proved it. the solution was a one piece ferrite or toroid as you've indicated. even if the vibrating would not bother you, the fact is they would be hitting each other at at xxx hertz and could eventually weaken and crack the ferrite halves.
.

My solution for the split shell ferrite vibration noise was to inject RTV into them to fill the voids. Another product that might help is a cable wrap. http://www.kitagawa-ind.com/rs_up/pdf/ECBR-CF_shohin3.pdf

I have some scrap (10 feet plus) from a deinstalled tool at work that I could send to someone with a RFI/EMI problem to try. http://farm9.staticflickr.com/8038/8031700393_711885b601_c.jpg

PM me.

Re: RFI Noise??

BB. wrote: »

ideally, the two halves should touch (bundle tie, snap housing, etc.)--Air gaps reduce the amount of flux going through the ferrite.

-Bill

Ideally, Yes...

The small gap between has little effect on the magnetic performance as the total impedance in hardly effected because the flux lines will deflect into the cores away from the gap unless the gap is a sizable fraction (10%+) of the wavelength of the signal. (assuming the overall coverage is close to 100%)

Re: RFI Noise??

It is generally considered that Type 43 material is the best for the RF frequency range of the OP's birdie/noise.

In my experience, 43 is also the most common, especially for these cable style large beads. Unfortunately, there are no specific makings on any of these parts, FWIW.
Opinions, Vic

Re: RFI Noise??

When I ordered replacement parts for the kits, this is how they came:



I haven't ordered them in bulk, maybe 10 at a time. The smaller ferrites didn't have numbers on the parts, just on the packaging.

'tis good to be lucky! :cool:

Re: RFI Noise??

do you have access to ceramic disc capacitors either from a store like radio shack or an old junk tv set? if so try placing a cap across the controller input leads and try with and without the ferrites. .001uf to .005uf should do well. even 500pf is ok to try. just remember you don't want to short across the leads as you have the full pv power across there in a tight space so be careful.