The RFI kit is designed to suppress RFI caused by Solar micro-inverters, power optimizer, and solar arrays by electrically isolating the “antenna” wires used to connect the various devices.The cabling between the PV array, the micro-inverters or power optimizers and their connection to the electrical bus combining their individual outputs can be considered “antennas” for the pulse switching circuits of the individual devices thereby causing radiation at very low fundamental frequencies with harmonics that can cause undesirable radio interference in the 1-30 MHz (and sometimes higher) frequency range.This interference may be objectionable to the owner of the solar installation as well as neighbors who may also experience the interference to their electronic devices. THE RFI KIT FILTERS ONLY SUPPRESS COMMON MODE CURRENT (SIGNALS) THAT ARE COMMON TO ALL WIRES IN THE CABLE, AND DOES NOT EFFECT INDIVIDUAL DIFFERENTIAL SIGNALS ON EACH WIRE. THE FILTERS HAVE NO EFFECT ON THE NORMAL SIGNALS CARRIED WITHIN THE CABLE. Power Optimizer RFI Ferrite cores (slip on) have the two (+/-) cables from the solar array module thru the middle of the core and the two wires hooked to the “string” connecting the optimizers together. Suppressing RFI on all wires in and out of the optimizers helps to reduce any broadband RFI “noise” generated in the SOURCE switching circuits (typically at 200-1000 KHz and harmonics thereof). Two ferrite filters are required for each optimizer – we recommended Part # PV-RFI-PO (includes two ring filters). See typical installation diagram below:Solar Power Optimizer/PV Module Noise Filters (2) - ID=1.4"
Iron powder cores are more stable than ferrites and do not saturate as easily so they are best for tuned circuits, filters, and high power inductors. They come in different “Mixes” for use at different frequencies. For best “Q” use the Mix specified for your frequency.To find the number of turns to give the desired inductance for your coil use the formula below:
Turns = 100 x 
Toroid Dimensions
To order specify core size and mix (e.g. T200A-2). Available in sizes that have µH per 100 turns shown in table.
All iron powder cores are special orders. Please allow one week for shipment after order received.
The iron powder cores shown in the above tables are primarily used for either high power feed line chokes for common mode current reduction or for 4:1 and 9;1 very high power transmission line transformers.
For high power feed line chokes, choose the inside diameter of the iron powder core closest to the transmission line outside diameter and use 6-20 cores at the junction with the antenna feed.
For 4:1 (50/200 or 75/300 ohm) transmission line transformers in the range of 1.8-30 Mhz, select the size appropriate for the power level as follows:
T200A x 2 = 1.5KW
T300A x 2 = 2.5KW
T400A x 2 = 5KW
Use Mix 2 for all the above transmission line transformers. Fully assembled and enclosed units are available for each of the power levels. Click HERE for information.
4:1 transmission line transformers using iron powder cores are typically used for ladder line to 50 ohm coax connections
For .1 – 2 Mhz wide band transformers use Mix 26 which has a higher permeability and requires less turns to achieve a given inductance. Mix 2 has almost constant permeability from 1-30 Mhz. Mix 26 has an initial permeability of 75 at .1 Mhz and gradually decreases to about 10 at 30 Mhz. For high power AM broadcast range (.5-1.7 Mhz) transformer, use Mix 26 to reduce the turn count.
Minimum order for iron powder cores is $50
Shipping on larger cores in quantity may be more than $10 – email/call for quote.