Special Features:
  • Custom permeability ferrite cores for widest bandwidth (1MHz to 50 MHz) & lowest energy loss (<0.2 dB)
  • High power handling capability (up to 10KW)
  • 'Current' and 'voltage' type available
  • Aluminum casing with SO239 connectors and two ceramic feedthrough post outputs for antenna
  • Dimensions: a x b x c
  • Mounting hole

Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms unbalanced (coaxial)
    For direct connection to yagi beam
    1 MHz to 50 MHz
    5 KW to 10 KW
    *5.5" x 3.8" x 2.3" (*6.8" including flanges)
Model W2FMI-4:1- HB50

1:1 Balun - 50 ohms balanced to 50 ohms unbalanced (coaxial)
    For 1/2 wave dipole or yagi beam
    For tranceivers, linear amplifiers, LC tuning networks
    1 MHz to 50 MHz
    5 KW to 10 KW
    *5.5" x 3.8" x 2.3" (*6.8" including flanges)
Model W2FMI-1:1- HBH50
The W2FMI-1:1 balun is generally designed to match 50-ohm coaxial cable to the balanced loads of center-fed half-wave diapoles or Yagi beam antennas. Feeding the balanced diapole with coaxial cable will upset the balance as one side of the antenna is connected to the shield while the other side is connected to the inner conductor. This results in reduction in gain, increase in VSWR and RFI interferences. Use W2fmi 1:1 balun to reduce these.
The W2FMI-1:1 is also used to match the unbalanced outputs of tranceivers and linear amplifiers to the input of a balanced L-C tuning network.
When to use and when not to use a 1:1 Balun:
Since feeding a center-fed half-wave diapole with coaxial cable creates a very small imbalance at the feedpoint (because the diameter of the cable is much smaller than the wavelength), a 1:1 balun is generally not needed in the HF and VHF bands. Experiments have found it to be needed only when the coaxial cable does not come away at right angles from the diapole (for the plane of an inverted V). A 45 degree angle created a considerable imbalance.
With Yagi beam antennas it is a different matter. Since hairpin matching networks are usually employed, the effective spacing at the feedpoint is greatly increased and a 1:1 balun is required. Its biggest effect is the retaining of the antenna's beam pattern by preventing radiation from the feedline.
It must be pointed up that a 1:1 balun should never be used on the second harmonic of a half-wave center-fed dipole (like an 80 meter dipole being used on 40 meters). The impedance can be as great as 10,000 ohms creating very high boltages which can bring about voltages breakdown and/or excessive heating.

1.5:1 Balun - 75 ohms balanced to 50 ohms unbalanced (coaxial)
    For 1/2 wave dipole at 0.22 wavelengths above ground
    *5.5" x 3.8" x 2.3" (*6.8" including flanges)
When a half-wave diapole is at a height of about 0.22 wavelengths above ground, its resonat input impedance is close to 75 ohms. A 1.5:1 balun then performs the perfect match to 50-ohm coaxial cable. Although a VSWR of 1.5:1 (without the balun) is not of breat importance, some personal satisfaction can be realized by using this balun.
Model W2FMI-1.5:1- HB75

2:1 Balun - 100 ohms balanced to 50 ohms unbalanced (coaxial)
    For 1/2 wave dipole at 0.22 and 0.33 wavelengths above ground
    For Quad Loop antennas which have resonance input impediance close to 100 ohms
    *5.5" x 3.8" x 2.3" (*6.8" including flanges)
Probably the most useful application of a 2:1 balun is in matching 50-ohm coaxial cable to the input of quad loop antennas. These broadband antennas generally have input impedances close to 100 ohms. When the half-wave diapole is at about 0.33 wavelengths above ground, its resonant input impedance is close to 100 ohms. This would create a VSWR of 2:1. Obviously, a 2:1 balun is needed here.
Model W2FMI-2:1- HB100

4:1 Balun - 200 ohms balanced to 50 ohms unbalanced (coaxial)
    For 2KW Log Periodic Beam Antennas
    For Folded Dipoles using 300 ohm ribbon at 0.17 wavelength above ground
    Multi-band antenna
    Off-center-Fed antennas
    1MHz to 50 MHz
    2KW to 10KW
The 4:1 balun finds use in matching 50-ohm cable to log periodic beam antennas, multi-band antennas and folded dipoles using 300 ohm ribbon at a height of about 0.17 wavelength above ground. A dual ferrite core version is also available for high power and for G5RV. For antenna tuners, please use HBHT200. The 4:1 HB/U200 is both a current and a voltage balun. The 4:1HB/U200 is uniquely designed to function both as balanced to unbalanced matching and unbalanced to unbalanced matching. It is particularly suited for off-center fed antennas.
Model W2FMI-4:1- HBM200
Model W2FMI-4:1- HB/U200

4:1 Antenna Tuner Balun
    For 10KW Antenna Tuners
    For High Power (10KW) Log Periodic Beam Antennas
    For High Power (10KW) G5RV Multi-band Antennas
    1MHz to 50MHz
The 4:1 baluns in antenna tuners can be subjected to very hostile conditions (mainly ver high impedances and hence, high voltages) depending upon the length of the transmission lines. Therefore special attention is paid to the desigh of the balun and the best length for one-half of the diapole and the feedline. For antenna tuners, experience has shown that a balun with a rather large powdered iron toroidal core, connected as a voltage (Ruthroff's design) balun, to the be preferred choice. These 10KW baluns can also be used for high power log periodic antenna and G5RV.
Model W2FMI-4:1- HBHT200

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