High Power rated at 1.5KW/3KW/5KW (option) PEP (FT8 mode at 1.5KW) Broad frequency range of 3-30 MHz for < 2:1 SWR into matched load Compact 4" x 4" x 2" (1.5KW) or 4" x 4" x 4" (3KW/5KW) light weight weatherproof enclosure Quick, easy deployment with either halyard hoist and side eyebolts or to stud outputs (all 1/4" stainless hardware) Choice of BALUN (balanced outputs) or UNUN (unbalanced output and ground) Model CB-2.25-1500, 3000, 5000 is a 2.25:1 (112:50 ohm) multi-core balun used to translate a 50 ohm input to 112 ohms at RF power levels up to 5000 watts PEP when used with a matched load such as single band delta loop, quad or loop skywire. This assembled balun features a multi-core configuration for increased power handling and flatter frequency response to over 30 MHz. With a matched 112 ohm load the SWR over the frequency range is very consistent from 3-30 MHz and SWR is less than 2:1 over the range allowing easy tuning by most radio internal antenna tuners or an external tuner.
For RFI common mode suppression use, mix 31 is effective from 1-300 Mhz, mix 43 works from 25-300 Mhz, Mix 61 is for 200-2000 Mhz, and mix 77 favors .1-50 MHz. These frequencies are those of the interfering signal to be eliminated, not the operating frequencies of the equipment to be protected. See Mix Selection for other applications.
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Bead dimensions are shown in the picture below and in the table as A, B, C
Ferrite Bead Dimensions
Application Note: Use impedances for each bead at your desired frequency to select number of beads needed for desired Z. For example if you have a 50 ohm RG-8 coax cable and want a choking impedance of 500 ohms at 10 Mhz, you can check the FB102 column (since FB102 will pass RG-8 through its center ID) at 10Mhz and find that Mix 31 has a Z of 108 ohms/bead and Mix 43 has a Z of 91 ohms/bead. For 500 ohms we would need 5 mix 31 beads or 6 mix 43 beads to have greater than 500 ohms. Mix 31 has better response below 10 Mhz but above 10 Mhz mix 31 and mix 43 are very close. If you need more Z, just use more beads in series on the cable or use more windings thru a larger ID bead (e.g. USE FB102-31 for 4 turns of RG-8X for 16X increase in Z per bead – see pictures below for examples). Use Mix 61 for VHF and above for RFI/EMI suppression and below 30 Mhz for multi-ratio impedance transformers (baluns/ununs). See Mix Selection for other applications.
For extra large cables use the FB400-31 which has an inside diameter of 3 inches (76mm).
Frequency Range Comparison Chart
(FB56-xx size)
Multi-turn Common Mode Choking Impedance Increase Example (FB56-43)
Ferrite Bead relative size comparison
Left to right sizes: FB56 (ID = .25″), FB102 (ID=.505″), FB103 (ID=.77″)
SLIP ON Sizes for Heliax and Coax Cable
Cascaded Common Mode Chokes/Line Isolators/1:1 Baluns
 RG58 4 turns on 2 FB102-31 for 2000 ohms choking impedance |
 RG58 12 turns on FT240-43 for 4000-6000 ohms choking impedance |
Handy Wire Size reference for ferrite bead sizes needed
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Connector already on cable? See Snap On Ferrite Beads for convenient installation on cables with connector already installed.