Iron Powder Cores

Ladder Line baluns are used to match the impedance seen at the end of the ladder line to a coaxial cable, usually 50 ohms, but a ladder line balun can also be used to match to 75 ohm coax like RG-6/U used for cable and satellite installations. While RG-6 doesn’t have the same power rating as larger cable, it is very useful for beverage antennas or receiving antennas which don’t carry a lot of power.

The impedance seen at the end of the ladder line will not be the same as the characteristic impedance of the ladder line (typically 300 or 450 ohms). Good ladder line antenna designs try to have the impedance at the end of the ladder line attachment to the balun close to 200 ohms so that a 4:1 balun can be used to match to 50 ohm coax.

A typical ladder line antenna is shown in the picture below:

Ladder Line antenna Diagram - Iron Powder Cores

Palomar Engineers has ladder line to coax 4:1 baluns in both kit form and also assembled in a variety of 1 watt to 10KW power levels to suit the needs of many customers. The ladder line baluns are designed for balanced output and are generally used at the end of a run of ladder line from the antenna. The baluns connect to the ladder line and then transition to coax cable to you antenna tuner or radio station.

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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.