BUY THIS KIT NOW TO SOLVE YOUR RFI PROBLEMS! WORKS WITH MANY BRANDS OF COMMERCIAL VHF RADIOS INCLUDING ICOM A120, A220, A220T. Quick installation - immediate RFI/noise reduction. No radio mods required. This kit will help reduce or eliminate: 1. Radio Frequency Interference (RFI) to electronic devices including instrumentation and GPS systems. 2. RFI from other electronic devices such as switching power supplies, LED instrument and cockpit lights, battery chargers, GPS and computer systems which generate common mode currents on your radio interface or coaxial antenna feed lines. 3. These filters help reduce SWR problems between transceiver and antenna. The DC power line filter helps keep common mode current out of the power line which could cause interference to other devices connected to the same power source. These chokes use a ferrite core material that is effective in suppressing RFI from transmitters and receivers experiencing a high noise floor in the 1-300 MHz range. The ferrite split bead filters are easy to use, don’t require modification of the protected equipment and work in almost all cases, even when plug-in filters fail. Kit Includes 2 noise reduction split bead (they snap on like a clam shell) filters for coax and AC/DC power/ standard 15 Pin connector cable. 3/4" whole ID - just wrap 2-3 turns of coax cable thru 1 bead and 2-3 turns of the DC power/15 Pin cable thru the other split bead. Does not affect signals carried by the cables, only the common mode interference noise is suppressed. For additional RFI suppression, use a feed line choke at the antenna feed point to suppress common current on the coax feed line during TRANSMIT and a CMNF-500-50 coax noise filter at the radio end of the coax to reduce common mode noise during RECEIVE. Visit our website for all your RFI needs! Note: Icom A220 radio shown NOT included in this kit.
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.