Twin-lead

Twin-lead cable is a two-conductor flat cable as a transmission line used to high-frequency signals (HF). It is made of two multi-Cu or copper-steel wire, held a precise distance from each other by a plastic (usually) polyethylene tape. The uniform beab stan manure of wires is the key for the function of the cable as the parallel transfer cable, no abrupt changes in the distance was high-frequency power back in the direction of the source to reflect.Twin-lead Also the plastic covers and isolates the wires. In 300 Ohm twin wire, is the most common type of wire in the Rule 20 or 22 gauge, approx. 7.5 mm (0.30 inches) apart.  Twin Lead less signal loss as a coaxial cable, the main competing form of transmission line , but is more susceptible to faults Twin-lead.

How it works Twin-lead

Twin Lead is a form of parallel wire symmetric transmission line. The separation between the two wires in a twin-lead is small compared to the wavelength of the radio frequency (RF) signal carried on the wire.  The RF current in a wire in the same size and in the opposite direction to the RF current in the other wire. It is therefore in the region of far-field far from the transmission line, the radio waves emitted by a wire are equal but opposite in the phase (180° phase shifted) to the waves that radiated by the other wire so that they overlap and cancel each other.  The result is that there is almost no net radiative energy emitted by the line.
In a similar way, any disturbing external radio waves equal to induce, in phase HF currents in the same direction, in the two wires. As the load on the centerd on the wires connected to only difference, counter-related flows in the wires a current in the load create. Thus the disturbing currents is lifted, ribbon cable does not have a tendency to get, radio noise. Twin-lead
However, if a piece of metal is sufficiently close to a double track line within a distance comparable with the wire distance, it is for the wire much closer than the other. As a result in the metal object on the RF current through a wire will be greater than the opposite induced current by the other wire is induced, so that the currents are no longer cancel. So in the near body can power losses in the double connection lines cause, by energy as heat is dissipated by induced currents. You will also find building radio noise in cables or metal objects in the vicinity of the two-wire line can be asymmetrical currents in the wires induce noise coupling in the line.

Flexible flat cable

Twin-lead - Chicken ladder

ladder line or "window" line is a variant of the ribbon cable that is similar with the exception that the polyethylene belt between the wires that you hold apart rectangular openings ( "window") cut in it. [1] [3] The line consists of two insulated wires with "shoots" made of plastic, you every few inches so that it appears a ladder. The advantage of the "Window" is that the line and also reduce the amount of surface on the dirt and moisture buildup lighten so that chicken ladder less susceptible to weather-related changes in the shaft resistance. The most frequent type of 450 Ohms Chicken ladder, a wire spacing of approximately one inch Twin-lead
ladder line also can be produced or DIY-designed as "open-wire line", consisting of two parallel wires with widely spaced plastic or ceramic insulating bars and with a characteristic impedance of 600 ohms or more. ribbon cable