50:450 ohm (9:1) CUBE™ Balun, 1.8-31 MHz, 5 KW, ladder line, ZEPP, T2FDProduct DetailsMPN: CB-9-5000Input ohms/Output ohms: 50 in / 450 outputFrequency Range < 2:1 SWR (MHz): 1-31PEP Power Rating (watts): 5000Model 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.
HF 1-61 MHz coax feed line common mode chokes
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.
1:1 feed line Chokes (also known as feed line current chokes, common mode chokes, line isolators, current mode chokes, and 1:1 baluns/ununs) are available in kit form or assembled form in a weatherproof Current Unun and Balun Enclosure which we call a CUBE™. All 1:1 chokes are ferrite based and are designed for 50 ohm coaxial cable input and 50 ohm output. 1:1 Ferrite toroidal or bead chokes have a higher choking impedance than our popular Sleeve Chokes and various models are available for specific frequency ranges and power levels.
1:1 Chokes are useful for choking common mode currents that may flow on the exterior of the coax cable shield while allowing the signals on the interior of the shield and the center conductor to flow unaffected and keeping the common mode current on the antenna. They isolate the coax shield and prevent it from becoming part of the antenna system.
1:1 Chokes are useful between balanced lines for center fed dipoles at their fundamental frequency (468/f (MHz), beam antennas with a 50 ohm balanced driven element, G5RV, loops, yagis, NVIS antennas, mobile installations, portable antennas and anywhere common mode current (or RFI) is a problem. They are also helpful between transmitter and linear amplifier or between linear amp and antenna tuner or as isolation chokes where higher choking impedance is needed (in the range of 2K-7K ohms).
1:1 Chokes are also very useful as feed line current chokes at the “radio end” of the antenna (we call them coax noise filters) where they choke/filter common mode current induced onto the coax shield from radiated waves (from your antenna, and other sources such as DSL routers, computer devices, plasma TVs, etc. originating in your house or your neighbor’s house). For RFI issues see RFI/EMI Solutions for general use or for specific radios and devices.
For best results we recommend a 1:1 choke at the “antenna end” of the coax and a coax noise filter at the “radio end” of the coax. (A side benefit is a reduction in noise level caused by common mode currents). 1:1 chokes are also available as Sleeve Chokes (Slip on or Snap on) for ease of installation and light weight on the antenna.