Iron Powder Cores

50:200 (4:1) CUBE™ Ladder Line/Balanced Antenna to Coax Balun, 1.8-31 MHz, 1500 Watts PEP, Zepp, G5RV, Beam

SKU CB-4-1500TS
In stock
Product Details

The CB-4-1500 Balanced output Balun is a 4:1 impedance transformer designed to step down balanced antenna loads from ladder line/dipole/beam feed point impedances of 600-50 ohms to 150-16.7 ohms unbalanced coax at full legal amateur power of 1500 watts PEP ICAS/500 watts FT8/RTTY from 1.8 to 31 MHz. When connected to an antenna tuner output capable of tuning a 3:1 SWR range (16.7-150 ohms for 50 ohm coax) the CB-4-1500AT provides a suitable range for antenna tuner adjustment to 1:1 SWR as seen on the input of the antenna tuner. Also works with 75 ohm coax as well.

The balun can be used to connect unbalanced 50 ohm coax to ladder line fed balanced antennas like a center fed zepp, log periodic beam, G5RV, full wave loops, etc. It is not meant to be used with unbalanced antennas like verticals, OCF antennas, etc, unless they are also fed with ladder line and the feed point impedance presented to the balun is in the range of 600-50 ohms.

The CB-4-1500TS includes a ground lug as the transformer is DC grounded, but RF isolated so that the ground lug can be used to as a sink to a ground rod to dissipate static electricity built up on the antenna and feed line.

Typical impedance transformation ratios measured for the CB-4-1500TS are shown in the graph below. Notice that the impedance transformer is useful up to 750 ohms and down to 50 ohms impedance at the ladder line feed point converting these impedances very near 4:1 from 1.8-31 MHz. This impedance transformation covers most feed point impedances seen at the end of the ladder line for typical ladder line fed HF antennas. Keep the coax to transmitter line as short as possible to minimize coax line losses.

CB 4 1500AT Product 2 - Iron Powder Cores

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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.