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Assuming the dielectric properties of the material inside the cable do not vary appreciably over the operating range of the cable, the characteristic impedance is frequency independent above about five times the shield cutoff frequency. For typical coaxial cables, the shield cutoff frequency is 600 Hz (for RG-6A) to 2,000 Hz (for RG-58C). [10]
The characteristic impedance of coaxial cables (coax) is commonly chosen to be 50 Ω for RF and microwave applications. Coax for video applications is usually 75 Ω for its lower loss. See also: Nominal impedance § 50 Ω and 75 Ω
The circuit shown in the bottom diagram only can model the differential mode. In the top circuit, the voltage doublers, the difference amplifiers, and impedances Z o (s) account for the interaction of the transmission line with the external circuit. This circuit is a useful equivalent for an unbalanced transmission line like a coaxial cable.
These traces were produced by a time-domain reflectometer made from common lab equipment connected to approximately 100 feet (30 m) of coaxial cable having a characteristic impedance of 50 ohms. The propagation velocity of this cable is approximately 66% of the speed of light in vacuum.
A terminating resistor for a television coaxial cable is often in the form of a cap, threaded to screw onto an F connector. Antenna cables are sometimes used for internet connections; however, RG-6 should not be used for 10BASE2 (which should use RG-58) as the impedance mismatch can cause phasing problems with the baseband signal.
Depending on the frequency range, coupling loss becomes less significant above 15 dB coupling where the other losses constitute the majority of the total loss. The theoretical insertion loss (dB) vs coupling (dB) for a dissipationless coupler is shown in the graph of figure 3 and the table below.
If a coil is made using coaxial cable near to the feed point of a balanced antenna, then the RF current that flows on the outer surface of the coaxial cable can be attenuated. One way of doing this would be to pass the cable through a ferrite toroid. The end result is exactly the same as a 1:1 current balun (or Guanella-type balun).
In an electrical or electronic circuit or power system part of the energy in play is dissipated by unwanted effects, including energy lost by unwanted heating of resistive components (electricity is also used for the intention of heating, which is not a loss), the effect of parasitic elements (resistance, capacitance, and inductance), skin effect, losses in the windings and cores of ...