Model CB-9-5000 is a 9:1 multi-core, balanced output balun housed in a NEMA enclosure box (4″ x 4″ x 2″) with top studs (TS) used to translate a 50 ohm input up to 450 ohms at RF power levels up to 5000 watts PEP when used with a matched load. With matched 450 ohm load the SWR over the frequency range 1 to 31 MHz is less than 2:1 on the coax feed side. All power rating are PEP, 100%, continuous digital modes are 30% duty factor rating of PEP, FT-8 digital mode rated at 1500 watts. Application note: If using 450 ohm ladder line on the output of the balun top studs, make sure the impedance seen at the balun end of the ladder line is near 450 ohms since the ladder line acts as an impedance transformer, the impedance at the end of the ladder line may be different than the characteristic 450 ohms of the ladder line. For example a 1/4 wavelength of ladder line will transform a high impedance at the antenna feed point to a very low impedance at the other end connected to the balun thus placing a very low impedance load on a balun expecting 450 ohms and such a load may damage the balun. The impedance seen at the balun output should be near 450 ohms for full power rating.
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.