Specifications
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HD-CCTV SYSTEM
Features of HD-SDI signal
The transmission method of HD-SDI uses Bitrate 1.485Gbit/s of SDI(Serial Digital Interface) method as a standard of SMPTE
292M dened by SMPTE(Society of Motion Picture and Television Engineer). The transmission of HD-SDI uses high frequency
of 750MHz due to large amount of data transferred per second. Compared to Analog video signal which uses less than 10MHz,
it is over 75 times dierences. The higher frequency means short wavelength of signal, and signal attenuation by distance will
be increased. So, the most important part in HD-SDI transmission is to minimize decrease of signal. To minimize decrease of
signal , user needs to select suitable coaxial cable for HD-SDI transmission.
Coaxial Cable
The coaxial cable consists of signal line with insulator sur-
rounding signal line and shield(outer conductor). The signal
line, metal, has resistance value and this resistance value can
be separated as resistance, capacitance and reactance. From
these 3 values characteristic impedance is decided, and
there are 50ohm and 75ohm impedance in Coaxial cable.
Video cable has minimum attenuation at 75ohm character-
istic impedance and can transfer signal farthest at that time.
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External diameter of signal line, permittivity of insulator and external diameter of insulator are the elements to maintain 75ohm
impedance.
Even though conventional Analog CCTV system consists of coaxial cable, user needs to check impedance of coaxial cable, quality
of insulator, shielding method and impedance of cable connector to apply HD-CCTV system using HD-SDI.
75ohm Impedance
The picture shows Attenuation according to Characteristic Impedance, Power and Volt-
age. HD-SDI transmission signal is very low voltage and the most important part in the
coaxial cable is signal decrease. If signal decrease is big, that means transmission distance
becomes short. So, 75ohm characteristic impedance cable which shows minimum atten-
uation should be used.
In contrast to HD-SDI signal, 50ohm characteristic impedance coaxial cable is used in area
of RF such as communication, measurement, antenna to deliver signal of higher voltage
and current even though signal decrease is bit fallen behind.
The main coaxial cable types and specications
RG-type coaxial cable
RG-type coaxial cables include RG-59, RG-6, RG-58, RG-8, etc. following the American coaxial cable standard. RG-58, RG-8 is 50ohm coaxial
cable and RG-59, RG-6 is 75ohm video coaxial cable. RG-59 means 4C high-foamed coaxial cable, and RG-6 means 5C high-foamed coaxial
cable. /U means normal cable and /T means triple shielded cable.
ECX-type coaxial cable
ECX-type coaxial cables include 3C-2V, 5C-2V, 7C-2V,
10C-2V etc., and they are dened in Korean domestic
standard KSC 3610. They are solid polyethylene insula-
tion type coaxial cable, and it is dierent from foamed
insulation type ones. 3, 5, 7, and 10 means the outer di-
ameter, C means 75ohm impedance, 2 means PE (poly-
ethylene), and V means braided-shielding.
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Impedance in Ohms
FB (T)-type coaxial cable
FB(T)-type coaxial cables include 3C-(H) FB (T), 4C-(H) FB
(T), 7C-(H) FB (T), 10C-(H) FB (T) etc., and they are de-
ned as foamed/high-foamed polyethylene insulation
coaxial cable in Korean domestic standard KSC 3617. 3,
5, 7, and 10 means the outer diameter, C means 75ohm
impedance, F means foamed PE insulation, B means
braided-shielding, and T means triple shield. Especially, HF means high-foamed, but the expression is a little dierent according to manufac-
turers. In case of HD-SDI transmission, high-foamed insulation type is better than ECX type, and HFBT/FBT type’s triple shielding shows better
signal attenuation performance.
For reference, FB(T) type coaxial cable shows the most cost eective performance in HD-SDI transmission because it has high-foamed insula-
tion and shielding as default suitable for high frequency. But, if the distance is short, every cable does not make problem. You may refer to the
standard signal attenuation vs. frequency band table provided from cable manufacturers. You may think that HD-SDI signal
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