BUY THIS KIT NOW TO REDUCE NOISE IN THE RECEIVER AND SUPPRESS INTERFERENCE TO/FROM OTHER ELECTRONICS ON YOUR VESSEL. Works on most marine HF transceivers including ICOM M700, M710, M800, M801, M802, M810, GM800 HF Transceivers up to 60 MHz. Also applicable to SEA 225 & 323, Furuno FS 1502, SGC SG-2000 and similar HF marine radios with external antenna tuners. Purpose. The RFI kit is designed to be installed on your radio transceiver to reduce Radio Frequency Interference (RFI) caused by common mode current on the outside of the coax braid at the output of your radio and AC/DC power cable and antenna tuner cable. This kit will help reduce or eliminate: 1. “Hot mic” RFI caused by poor grounding of antennas or common mode currents from linear amps feeding unbalanced (coax fed) antennas without baluns/line isolators. 2. RFI to other electronic devices including audio/video systems, computers, marine electronics, etc. A side benefit is a reduction in noise floor in your receiver depending on the amount of noise being introduced by common mode currents (which are blocked/reduced by the chokes in this kit). These chokes use a special mix of ferrite core material that is effective in suppressing radio frequency interference from transmitters and high noise floor on receivers. The split beads beads are easy to use, don’t require modification of the protected equipment and work in almost all cases, even when plug-in filters fail. Use of the chokes often helps cure SWR problems between transceiver and antenna tuner s used on marine systems. The DC power line choke helps keep common mode current out of the power line which could cause interference to other devices connected to the same power line if not suppressed. Included are the following chokes and installation guidelines: RF Input/Output: Antenna feed line choke installed between radio and antenna tuner coax to reduce noise into receiver and suppress RFI. Includes double barrel male connector for joining choke directly to antenna tuner. DC Input: 1.4" inside diameter filter ring – coil 3-7 turns of DC power cable through center Antenna tuner cable: Two 1/2 snap on for 1-2 turns through center at each end of cable.
$89.95
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.