Understanding coaxial cable types — RG6, RG58, RG174 — and their impedance specifications is essential for anyone working with RF systems, video signals, antenna installations, or high-frequency electronics. The “RG” designation (Radio Guide) describes a specific cable construction including impedance, capacitance, and physical dimensions. This guide covers all major coaxial cable types, their impedances, applications, and India-specific availability.
Table of Contents
- What Is Coaxial Cable?
- 50 Ohm vs 75 Ohm: Why Impedance Matters
- RG58: The Versatile 50Ω Workhorse
- RG174: Miniature Coax for Electronics
- RG6: The TV and Satellite Standard
- RG8 and LMR-400: High Power RF
- Coaxial Connectors: SMA, BNC, F-Type, N-Type
- India Sourcing and Pricing
- Frequently Asked Questions
What Is Coaxial Cable?
A coaxial cable has a central conductor surrounded by a dielectric insulator, an outer braided or foil shield, and a protective jacket. The coaxial structure provides excellent shielding from external electromagnetic interference and maintains consistent characteristic impedance along the cable’s length — critical for RF signal integrity.
50 Ohm vs 75 Ohm: Why Impedance Matters
Coaxial cables come in two main impedance families: 50Ω (for RF transmitters, test equipment, networking) and 75Ω (for video signals, cable TV, satellite). Mixing impedances causes reflections (VSWR) that reduce signal power and cause signal distortion. Always match cable impedance to your system:
- 50Ω systems: Amateur radio, professional RF, Wi-Fi antennas, oscilloscope probes, test equipment, military/aerospace
- 75Ω systems: Cable TV (CATV), satellite dish installation, composite/component video, broadcast video
RG58: The Versatile 50Ω Workhorse
RG58 is the most common 50Ω coaxial cable for general RF work. It’s used in amateur radio, laboratory RF setups, Ethernet (10BASE2, now obsolete), and as test cable for oscilloscopes and network analysers.
RG58 Specifications
- Impedance: 50Ω
- Centre conductor: 19-strand 0.9mm (RG58/U) or solid 0.9mm (RG58A/U)
- Dielectric: PE (polyethylene)
- Shield: Braided copper
- Outer diameter: 4.95mm
- Attenuation at 100MHz: ~5 dB/100m
- Max frequency: 1 GHz practical
- India price: ₹15–35 per metre
RG174: Miniature Coax for Electronics
RG174 is a miniature 50Ω coaxial cable, thinner and more flexible than RG58. It is widely used in maker electronics for connecting small SMA antenna pigtails to Wi-Fi modules (ESP8266, ESP32), GPS receivers, and Bluetooth modules.
RG174 Specifications
- Impedance: 50Ω
- Outer diameter: 2.8mm (much smaller than RG58)
- Attenuation at 100MHz: ~12 dB/100m (higher loss than RG58)
- Max frequency: 500 MHz practical (higher loss at GHz frequencies)
- India price: ₹12–25 per metre, pigtail assemblies ₹50–150
RG174 pigtails with U.FL (IPEX) to SMA connectors are the most commonly used accessory for connecting Wi-Fi and LTE module antennas in embedded systems. Available from Amazon India and Robu.in.
RG6: The TV and Satellite Standard
RG6 is the 75Ω cable used for cable TV (CATV), satellite dish, and home video distribution across India. The DTH (Direct-to-Home) satellite installation in every Indian home uses RG6 cable running from the dish to the set-top box.
RG6 Specifications
- Impedance: 75Ω
- Centre conductor: 18 AWG solid copper-clad steel (CCS)
- Shield: Aluminium foil + braided shield (dual or quad shield versions)
- Outer diameter: 6.9mm
- Connector type: F-type connector (standard for India DTH installations)
- India price: ₹8–20 per metre (Finolex, Polycab brands at electrical shops)
RG6 is used in: CATV installations, DTH satellite (Tata Sky, Airtel, Dish TV), CCTV camera runs (75Ω video signal), and home theatre component video connections. Available at every hardware and electrical store in India.
RG8 and LMR-400: High Power RF
For high-power amateur radio and professional RF installations, thicker low-loss cables are used:
- RG8/RG8X: 50Ω, 10.3mm diameter, suitable for amateur radio HF/VHF transmitters up to 1kW
- LMR-400: 50Ω, 10.3mm, superior to RG8 with only 2.7 dB/100m at 450 MHz. Used in cellular base stations and amateur radio antenna runs. Available from RF component importers in India at ₹150–300/metre.
Coaxial Connectors: SMA, BNC, F-Type, N-Type
| Connector | Impedance | Max Freq | Application |
|---|---|---|---|
| SMA | 50Ω | 18 GHz | Wi-Fi, GPS, SIM modules, drones |
| BNC | 50/75Ω | 4 GHz | Oscilloscopes, CCTV, test equipment |
| F-Type | 75Ω | 3 GHz | Cable TV, DTH satellite India |
| N-Type | 50/75Ω | 18 GHz | Amateur radio, cellular antennas |
| U.FL/IPEX | 50Ω | 6 GHz | PCB-mount micro connector for Wi-Fi/LTE modules |
India Sourcing and Pricing
- RG6 (75Ω): Available at every electrical shop — Finolex, Polycab, and generic brands. ₹8–20/m. Best quality: Belden India-distributed or Commscope.
- RG58 (50Ω): Electronics component shops (SP Road Bangalore, Lamington Road Mumbai), or online via Amazon/Flipkart. ₹15–35/m.
- RG174 pigtails (SMA, U.FL): Amazon India, Robu.in, Zbotic. ₹50–150 per pigtail assembly.
- LMR-400, LMR-200: RF-specialised importers, Mouser India. ₹150–400/m.
- SMA connectors: Crimp-type SMA connectors for RG58 — ₹25–80 each from electronics component shops.
Frequently Asked Questions
Can I use RG6 (75Ω) cable for my Wi-Fi antenna?
Not recommended. Wi-Fi (2.4/5 GHz) systems are designed for 50Ω impedance. Using 75Ω RG6 creates an impedance mismatch, causing reflections that reduce transmitted/received power and can damage transmitter front-ends. Use 50Ω RG174 or RG58 pigtails for Wi-Fi antenna connections.
Why does my CCTV system use BNC connectors on RG59 cable?
Analogue CCTV cameras use composite video signals on a 75Ω transmission line. RG59 (75Ω, thinner than RG6) with BNC connectors is the traditional CCTV standard. Modern HD-TVI, HD-CVI, and AHD cameras also use 75Ω coaxial (RG59 or RG6) with BNC connectors. BNC at 75Ω is the video industry standard worldwide.
How do I crimp an SMA connector onto RG58 cable?
You need an SMA crimp connector sized for RG58 and a proper coaxial crimp tool. Steps: strip jacket 25mm, trim braid back 10mm, fold braid back over jacket, trim dielectric to 5mm, tin centre conductor. Insert into SMA crimp body, position crimp ferrule over folded braid, crimp with hex die. An SMA crimp tool costs ₹800–2,000 in India and is available from RF accessory suppliers or Amazon India.
What is the maximum cable run for RG6 in an Indian DTH installation?
RG6 attenuation at satellite IF frequency (950–2150 MHz) is approximately 25–35 dB per 100 metres. Maximum practical run to maintain adequate signal level: 30–50 metres from dish to set-top box without amplification. For longer runs (apartment buildings, multi-storey), use a distribution amplifier (masthead amplifier) or active satellite distribution system. Available from DTH installers and electrical supply shops in India at ₹800–3,000.
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