|Don's Home Home & Garden Coaxial Cable Contact|
Coaxial Cable (coax) is the most popular type of transmission line for TV, CB and amateur radio. 300 ohm twin lead is also popular.
The coax connects the receiver or transceiver to the antenna, dish or commercial Cable TV line.
Coaxial Cable can come in many grades based on the type of shield, conductors and diaelectric.
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Foam dielectric - More flexible, higher Velocity of Propagation.|
Stranded core - more flexible.
larger core - lower resistance, and attenuation.
Shielding - Layers and quality reduce noise and signal leakage.
U - Solid Core A/U - Stranded Core 3dB loss represents 1/2 the original signalSpecs within a cable type vary based on conductor size, construction and dialectric type.
40 m ham = 7 MHz 10 m ham = 29 MHz CB = 27 MHz (11 m) VHF TV = 54-88 MHz (4.3 m), 174-216 MHz (1.5 m) 2 m ham = 144-148 MHz UHF TV = 470-806 MHz Satellite TV = 950 to 1450 MHz - The higher frequency satellite signals are converted by the Low Noise Block Converter (LNB) at the dish to L-Band (1 GHZ) for transmission to the receiver.Velocity Factor of Propagation (Vp) Through Coaxial Cable
The velocity factor is the speed at which an RF signal travels through a material compared to the speed the same signal travels through a vacuum. The velocity of propagation is inversely proportional to the dielectric constant. Lowering the constant increases the velocity.
Generally, the higher the velocity factor, the lower the loss through a coaxial cable.
General Rules for Coaxial Cable
D = diameter of insulation under the shield
d = diameter of inner conductor.
Velocity Factor, Velocity of Propagation, Vp
The higher the velocity factor, the lower the loss through the cable.
Raising the D/d has no effect on Vp
Raising the dielectric constant lowers Vp
Raising the D/d ratio lowers capacitance
Raising the dielectric constant raises capacitance
Impedance Raising the D/d radio raises impedance
Raising the dielectric constant lowers impedance
Attenuation or Loss
Raising the D/d ratio lowers attenuation
Raising the dielectric constant raises attenuation
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Stranded wire core is more flexible.
Solid or Stranded doesn't affect Propagation factor
Some cables use copper covered steel (CCS) for strength.
Quad cable (two layers of foil and braid) is not necessairly better depending on the quality of the foil and braid.
attenuation- Signal loss CATV - Community Antenna television Television service to homes via radio frequency signals sent through fixed optical fibers or coaxial cables as opposed to over-the-air radio waves. CCS - Copper Coated Steel CCTV - Closed-circuit television Typically used for surveillance cameras. CFEP - Cellular Fluorinated Ethylene/Propylene copolymer CL2 - Class 2 cable - low voltage (NEC Type) CL2P - Class 2 plenum rated CM - Communications Cable dielectric constant - relative permittivity or a measure of how well the material insulates electrically. FEP - Fluorinated Ethylene/Propylene copolymer (Teflon®) HD-SDI - High Definition SDI MP - Multipurpose cable LL - Low Loss (same as LMR) LMR - standard is a UV Resistant Polyethylene jacketed cable designed for 20-year service outdoor use. The bending and handling characteristics are significantly better than air-dielectric and corrugated hard-line cables. LLMR® is a trademark of Times Microwave Systems. MATV - Master Antenna TV NEC - National Electric Code Article 800 covers multi-purpose and communication cable. Article 820 covers community antenna television and RF cable. CATV cable substituted with multi-purpose or communication listed coaxial cable. Article 800 800-3(b)1 CMX Communications cable limited use 800-3(b)1 CM Communications cable 800-3(b)2 CMR Communications riser cable 800-3(b)3 CMP Communications plenum cable OF - PE - Polyethylene (Solid and Foam) PU - Polyurethane PVC - Polyvinyl Chloride SBC - Solid Bare Copper SDI - Serial Digital Interface (TV) Vp - Velocity Factor, Velocity of Propagation STC - Stranded tin copper See: Glossary of terms - Coax at Belden
Attenuation & Power Handling Calculator at TimesMicrowave.com
Ham Radio Coaxial Cable Power Handling and Loss Specifications
CCTV Cable and Differences in Coaxial Cables at West Penn Wire
Attenuation at QSL
Coax Attenuation Chart at W4RP
Attenuation Chart at Davis RF wire
Coaxial Cable at TWAcomm.com
Coaxial Cable at ElectroCables.com
Video Cables from the Inside Out