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Professional Cables



DEFINITIONS OF THE ELECTRICAL FEATURES OF A CABLE

CAPACITY:
The capacity of a cable is the value that indicates the properties of the dielectric to store electrical charges between the central conductor and the screen. The capacity is expressed in pF (picofarad, 1 pF = 1x10-12 F). The higher is the capacity the more high frequencies are attenuated along the cable. So the best cable is the one that has the lowest capacity.
(at the same impedance).

IMPEDANCE:
It indicates the opposition of a transmission line to the flow of electrons, it is expressed in Ohms and is derived from the relation between the voltage V and the current I at any point of the coaxial cable.

ATTENUATION:
It quantifies the loss of signal and is expressed in dB (Decibels). In reception and transmission (power)  the attenuation is given by 10xlog10 (Pin / Pout).    The signal is halved every 3 dB.

SRL - STRUCTURAL RETURN LOSS:
It measures the intensity of reflected waves (toward the source) inside the cable. The SRL is highly affected by the imperfections of the impedance in one or more points along the transmission line.

SCREENING EFFICIENCY:
It generally indicates the ability of a screen to prevent electromagnetic interference, which can “contaminate” the signal along the cable and vice versa that the signal could be radiated outside of the cable. At high frequencies (> 30 MHz), this is expressed in “Screening Attenuation” (SA) and the unit of measurement is the decibel. At low frequencies (< 30 MHz), it’s called transfer impedance (Zt) and it is expressed in mOhm/m.
The lower is the value in milliohms, the better  is the cable performance.
In the old RG cables, the maximum screening efficiency obtained is 80 dB, while in our new cables is >105 dB (A++ CLASS).
The Zt in the old RG cables does not drop below 13 mΩ/m (RG 214), compared to 0.9 mΩ/m of our new cables:
 

VELOCITY RATIO:
It’s the speed which the signal travels at, along the cable, and it is expressed as a percentage of the light speed. In the cables with plain polyethylene, the best value reached is 66%, against the  85% of the cables with foamed polyethylene dielectric.
 

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