Iron Powder Cores

Icom IC-7300 Transceiver Deluxe RFI Kit - 5 Noise Reduction Filters + Coax Noise Filter

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BUY THIS KIT NOW TO SOLVE YOUR RFI PROBLEMS! WORKS WITH MANY BRANDS OF HAM/COMMERCIAL HF RADIOS INCLUDING THE ICOM 7300. This kit is an improvement over our standard Icom 7300 RFI Kit and now includes our very effective Coax Noise Filter, (CMNF-500-50) to reduce common mode noise picked up by the antenna feed line coax as well as individual filters for the DC power line, and other cables including DIN Plug, Remote/CIV, AMP Send/ALC, and USB.

This kit will help reduce or eliminate:

1. Radio Frequency Interference (RFI) to electronic devices including audio/video systems, computers, telephones, garage door openers, alarm systems, and home appliances, in your house or your neighbor’s house.

2. RFI from other electronic devices such as switching power supplies, LED and fluorescent lights, battery chargers, Ethernet cables, solar systems, kitchen appliances, and cable/satellite TV systems which generate common mode currents on your radio cables.

3. These filters help cure SWR problems between transceiver and a linear amp and between transceiver and antenna tuner or direct to 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 beads and ring 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 a low frequency noise reduction ring filter (works great on DC switching power supplies too!) for AC/DC power, 4 snap on filters (1/2" ID) for I/O cables and the CMNF-500-50 coax noise filter and double male barrel connector for direct attachment to your radio antenna connector. The CMNF-500-50 provides up to 38 dB (6 "S" units) of common mode noise attenuation.

This Kit features Quick installation - immediate RFI/noise reduction. No radio mods required.

For additional RFI suppression, use a feed line choke(like the MC-1-500 for 500 watts or the MC-1-3000 for powers up to 3KW PEP) at the antenna feed point to suppress common current on the coax feed line during TRANSMIT.

If you use a linear amplifier use a Palomar Engineers Amplifier RFI kit (part# RFI-LA-GAC) for additional RFI interference suppression.

Icom 7300 RFI Kit Flyer Download

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Iron Cores 150x150 - Iron Powder CoresIron 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 iron core formula 300x14 - Iron Powder Cores

Toroid Dimensions

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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.