Specifications

74
COMTEK Baluns
COMTEK Baluns were inspired by the writings of Jerry Sevick W2FMI, published in
his book Understanding, Building and Using Baluns and Ununs. COMTEK baluns are
value-engineered to provide maximum performance at minimum cost while providing
a superb, e icient match between unbalanced coax and balanced antennas.
• Design inspired by Jerry Sevick W2FMI with modern improvements from
DX Engineering’s in-depth balun R&D
• Unique high voltage compensating capacitors for unequalled SWR bandwidth
• Outstanding ferrite mix coated toroid core with special design to accommodate
close coupling without excessive stress
• Exceptionally high and consistent common-mode impedance across the specified
band width provides isolation where it is needed most
• Special wire size selection and Teflon®-insulated wire sleeves provide exact
impedance matching and superb insulation, unlike common Thermaleze® wire
• Typical insertion loss is less than 0.2 dB
• Power handling from 3 kW continuous to 7 kW intermittent, depending on model
May be used to 54 MHz with reduced ratings
• Gasketed SO-239 connectors are silver plated with Teflon® insulation.
• All hardware is Stainless Steel. Studs are 1/4"-20
• COMTEK Baluns are sealed in a weatherproof 4" x 4" x 2" NEMA box which makes
an excellent outdoor enclosure
1:1 Dual Wire/Single Core
COM-BAL-11130E 3 kW, 1.8 to 54 MHz, Side Eyebolts ....................................... $56.95
COM-BAL-11130ET 3 kW, 1.8 to 54 MHz, Side/Top Eyebolts ............................... $56.95
COM-BAL-11130S 3 kW, 1.8 to 54 MHz, Side Studs ............................................ $56.95
COM-BAL-11130T 3 kW, 1.8 to 54 MHz, Top Studs ............................................. $56.95
1:1 Coax/Single Core
COM-BAL-11150E 5 kW, 1.8 to 54 MHz, Side Eyebolts ....................................... $61.95
COM-BAL-11150ET 5 kW, 1.8 to 54 MHz, Side/Top Eyebolts ............................... $61.95
COM-BAL-11150S 5 kW, 1.8 to 54 MHz, Side Studs ............................................ $61.95
COM-BAL-11150T 5 kW, 1.8 to 54 MHz, Top Studs ............................................. $61.95
1:1 Dual Wire/Dual Core
COM-BAL-11140T 5 kW, 1.8 to 54 MHz, Top Studs ............................................. $78.95
COM-BAL-11140S 5 kW, 1.8 to 54 MHz, Side Studs ............................................ $78.95
1:1 Coax/Dual Core
COM-BAL-11150DS 5 kW, 1.8 to 54 MHz, Side Studs ............................................ $78.95
COM-BAL-11150DT 5 kW, 1.8 to 54 MHz, Top Studs ............................................. $78.95
4:1 Dual Wire/Single Core
COM-BAL-41130E 3 kW, 1.8 to 54 MHz, Side Eyebolts ....................................... $66.95
COM-BAL-41130ET 3 kW, 1.8 to 54 MHz, Side/Top Eyebolts ............................... $66.95
COM-BAL-41130T 3 kW, 1.8 to 54 MHz, Top Studs ............................................. $66.95
COM-BAL-41130S 3 kW, 1.8 to 54 MHz, Side Studs ............................................ $66.95
4:1 Dual Wire/Dual Core
COM-BAL-41150T 5 kW, 1.8 to 54 MHz, Top Studs ............................................. $93.95
COM-BAL-41150S 5 kW, 1.8 to 54 MHz, Side Studs ............................................ $93.95
COM-BAL-41150E 5 kW, 1.8 to 54 MHz, Side Eyebolts ....................................... $93.95
Contact DX Engineering Customer Support to discuss your application or for recommendations.
Jerry Sevick W2FMI-inspired COMTEK Baluns
W2FMI Series Baluns
When properly connected to balanced antenna loads like symmetrical dipoles,
unbalanced coaxial feedlines must have exactly equal and opposite currents on the
shield and center conductors. COMTEK baluns are value-engineered to provide
maximum performance at minimum cost while providing a superb, e icient match
between unbalanced coax and balanced antennas.
Balanced current distribution along the halves of the antenna assures correct pattern
shape and antenna e iciency. Current baluns add common-mode isolation between
the antenna and coaxial feedline.
The expected figure-8 dipole azimuth pattern cannot be achieved unless RF current
is flowing equally on both halves of the dipole. The COMTEK current baluns force
equal current to flow and prevent high values of common-mode feedline current.
This eliminates pattern distortion, unpredictable performance, RFI, and noise pickup
from nearby sources like TV sets and computers.
Baluns come in ratios for e ective SWR matching between the 50 Ω coaxial
transmission line and the antenna feedpoint based on the feedpoint impedance.
COMTEK baluns have been designed to provide the lowest possible SWR match
across the specified frequency range.
Current baluns isolate or add impedance to unwanted common-mode current paths,
reducing or controlling common-mode current. Current baluns are the best choice
in almost all situations because they work better in most real-world systems by
isolating the input and output connections.
Contrary to some published information, a high common-mode impedance across a
wide frequency range is absurd, if not unachievable. The highest impedance values
are most useful at lower frequencies, while lesser impedance values are more than
adequate at the high end of the HF range. In most cases, baluns are installed as close
as possible to a balanced-to-unbalanced transition point.
Balanced Current With No Balun
Baluns, UNUNs & Chokes
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