What coax does
Coaxial cable (“coax”) carries radio-frequency power between your radio and your antenna. It has a center conductor, an insulating layer, a shield, and an outer jacket. The shield keeps the signal contained, which is why coax is popular for station wiring. Coax is also a part of your antenna system, not just a wire: its loss, impedance and condition all affect performance.
Why 50 ohms
Most ham transceivers and most common ham antennas are designed around 50 ohms. Using 50-ohm coax between them keeps the system matched. Cable TV and satellite cables such as RG6 and RG59 are typically 75 ohms. Using them with a 50-ohm system creates a mismatch; it may work for a short run in a pinch, but it is not a good choice and the shielding and connectors usually differ too.
Are RF and coax the same thing?
No. RF (radio frequency) refers to the signals themselves, while coax is one kind of cable used to carry them. Other kinds of feedline exist, such as ladder line, and there are many coax types.
How to tell RG6 from RG59
Check the printing on the jacket first. RG6 is generally thicker, with a larger center conductor and often a foam dielectric and a heavier shield; RG59 is thinner. If the markings are missing, compare diameter against a known cable. Either way, both are normally 75-ohm cable.
Common types for ham use
| Cable | Typical use | Notes |
|---|---|---|
| RG-174 | Very short jumpers, handhelds | Thin and lossy |
| RG-58 | Short HF runs, portable | Flexible, but lossy at VHF/UHF |
| RG-8X | Moderate runs, mobile | Lighter than RG-8 |
| RG-213 / RG-8 | HF and VHF, longer runs | Thicker, lower loss |
| LMR-400 and similar | VHF/UHF and long runs | Low loss, less flexible, check connector compatibility |
Brand names such as LMR are manufacturer product lines; equivalents from other makers exist. See our coax cable loss chart for approximate figures.
Choosing by band and run length
Loss rises with frequency and length. On HF, a short run of RG-58 may lose little. On 2 meters and 70 cm, the same cable can lose a significant share of your power over a longer run, so thicker cable is usually advised. If you mount an antenna high for better range, as discussed in the height of a VHF radio antenna, remember that the longer feedline you add costs signal.
Connectors
- PL-259 / SO-239 (UHF): common on HF gear. Fine for HF; less ideal at UHF.
- N connectors: popular for VHF/UHF and outdoor use, with good weather performance.
- BNC: quick-connect for test gear and some portable radios.
- SMA: found on handhelds; be careful of male/female differences.
Poor connector installation is a common cause of problems. Take your time soldering or crimping, and use the right connector for your cable size.
Installation tips
- Avoid sharp bends; they can damage the cable.
- Weatherproof outdoor connectors.
- Make a drip loop so water does not run into the shack.
- Use ferrite chokes or a choke balun where common-mode current is a concern.
- Replace cable that has cracked jackets or discolored braid.
Common questions
What is a good antenna for HF? A dipole or vertical is a typical beginner choice. See types of ham radio antennas.
How to set up a ham radio antenna? Pick a design, mount it clear of obstacles, connect with suitable coax, and check SWR. The steps are in ham radio and antenna basics.