What Is a 50 Ohm Coaxial Cable? Types and Selection Criteria
A 50 ohm coaxial cable is a coaxial RF cable with a characteristic impedance of 50 ohm that connects radio, GSM, WiFi and GPS equipment to its antenna.
A 50 ohm coaxial cable is a coaxial cable with a characteristic impedance of 50 ohm that carries radio frequency (RF) signals between a transmitter, receiver and antenna. It is the feed line between the device and the antenna in radio, GSM/4G modem, WiFi, RFID and GPS systems. It does not replace the 75 ohm cables used in TV and satellite installations or RG59-type camera cables: an impedance mismatch reflects part of the signal back.
Types of 50 ohm coaxial cable
| Type | Outer diameter | Dielectric and shield | Attenuation at 900 MHz (dB/100 m) | Use |
|---|---|---|---|---|
| RG174 | 2.85 mm | Solid PE, 95% braid | 109.3 | Inside equipment, very short links |
| RG58 C/U | 4.95 mm | Solid PE, 95% braid | 66.0 | Short, flexible links |
| RG213 U | 10.3 mm | Solid PE, 95% braid | 25.75 | Long, high-power runs |
| Reçber RWC 240 (low loss) | 6.0 mm | Foam PE, foil and 85% braid | 24.8 | Loss close to RG213 in a thin cable |
| Reçber RWC 400 (low loss) | 10.2 mm | Foam PE, foil and 85% braid | 13.02 | Long antenna runs |
The values are the maximum attenuation in the Reçber datasheets; the low loss rows come from the Reçber RWC 240 and RWC 400 datasheets. A foam dielectric raises the velocity of propagation from 66% to 84–85% and lowers the loss.
Selection criteria
- Attenuation: Loss rises with frequency and length. Line loss = the dB/100 m value × length (m) / 100, plus connector losses; 3 dB means half the power. On a 30 m run at 900 MHz, RG58 loses about 19.8 dB, RG213 7.7 dB and RWC 400 3.9 dB.
- Connector: Connectors are made for a specific cable type; an RG58 connector does not fit RG213. Common types are BNC, TNC, SMA and N; UHF (PL-259) is also used on radio lines. BNC also comes in a 75 ohm version; check that the connector is 50 ohm.
- Jacket: PVC is for indoor use, halogen-free (HFFR) for enclosed spaces where low smoke and halogen-free gas are required, and PE for outdoor and underground use.
- Shield: Low loss types combine foil and braid; the Reçber RWC datasheets give at least 90 dB screening attenuation at 30–3000 MHz.
- Bending: The minimum bend radius is 10 x D: about 50 mm for RG58 and 103 mm for RG213.
Common installation mistakes
- Using a 75 ohm cable or connector: A 50/75 ohm mismatch causes a reflection of about 1.5 SWR on the line and extra loss.
- Extending the antenna cable unnecessarily: Extending a 9 dBi 4G antenna with 10 m of RG58 at 900 MHz loses about 6.6 dB, most of the antenna's gain. On long runs, choose a low loss cable with low attenuation or move the device closer to the antenna.
- Terminating the shield poorly: If the braid does not seat fully in the connector body, shielding and impedance suffer; use a connector and crimp tool made for the cable type.
- Leaving outdoor connections exposed: Water entering at the connector travels along the braid and permanently increases loss; seal outdoor connections with waterproof tape.
Standards
- MIL-C-17 (now MIL-DTL-17): The RG174, RG58 and RG213 type names come from this US military specification; the Reçber RG datasheets state MIL-C-17F and MIL-C-17G.
- IEC 61196: Specification series for coaxial communication cables; listed in the Reçber RWC datasheets.
- EN 60332-1-2, EN 60754-1/2, EN 61034-2: Flame propagation, corrosive gas and smoke density; only the first applies to PVC jackets, all three to halogen-free jackets.
50 ohm coaxial cables in the catalog
The 50 Ohm Coaxial Cables category has 9 active products, all sold by the metre.
| Brand | Type | Jacket | Product |
|---|---|---|---|
| Reçber Kablo | RG174 | PVC | Reçber RG 174 Cu PVC Cable |
| Reçber Kablo | RG174 | Halogen-free | Reçber RG 174 Cu HF Cable |
| Reçber Kablo | RG58 C/U | PVC | Reçber RG 58 C/U PVC Cable |
| Reçber Kablo | RG58 C/U | Halogen-free | Reçber RG 58 C/U HF Cable |
| Reçber Kablo | RG213 U | Halogen-free | Reçber RG 213 U HF Cable |
| Reçber Kablo | LWR 240 | PE | Reçber LWR 240 PE Cable |
| Reçber Kablo | LWR 400 | PE | Reçber LWR 400 PE Cable |
| Mekas Kablo | RG213 U | PVC | Mekas 50 Ohm PVC Coaxial RG213 U Cable |
| Mekas Kablo | RG213 U | Halogen-free | Mekas 50 Ohm Halogen Free Coaxial RG213 U Cable |
Frequently asked questions
What is the difference between 50 ohm and 75 ohm coaxial cable?
50 ohm cable is used on transmitter-to-antenna lines such as radio, GSM and WiFi; 75 ohm cable is used for TV, satellite and video distribution. One cannot replace the other.
RG58 or RG213?
RG58 is 4.95 mm and flexible, suited to short links. RG213 is 10.3 mm; at 900 MHz it loses about 40% of what RG58 loses and is chosen for long runs.
Why does low loss cable lose less?
Its dielectric is foam PE. Foam has lower loss than solid PE and allows a thicker centre conductor within the same outer diameter. The Reçber RWC 400 has a solid copper conductor; at 900 MHz it runs at about half the loss of RG213 of the same thickness.
Which cable should I use for a WiFi antenna?
Loss rises with frequency: the Reçber RWC 400 datasheet gives 13.02 dB/100 m at 900 MHz, 23.30 at 2500 MHz and 38.92 at 5800 MHz. For runs longer than a few metres, choose low loss cable and calculate the loss from the length.