A CB radio needs 50 ohm coax with a PL259 plug on each end, mating into the SO239 socket on the set. RG58 at 6mm suits short mobile runs, Mini8 at 7mm is the middle step, and RG213 at 9mm gives the lowest quoted loss for long base station runs.
The feeder is the part of a CB install nobody inspects, and the first thing blamed when transmissions sound thin. A dull solder joint, or a flat spot where the boot lid closes, wastes power on every transmission.
What coax does a CB radio actually need?
Two things matter. The cable must be 50 ohm, because the radio, the antenna and the test gear are all built around that figure. Our RG58 military spec cable is listed at 50 ohms, and so are the Mini8 and the RG213. The second is the fitting: CB coax terminates in a PL259 plug that screws into an SO239 socket, the connection used across the coax cable range, the mounts and the two way coax switch. None of that changes with the licensing: 27 MHz CB here is licence exempt at 4 watts on FM and AM, covered in our guide to whether CB radio is legal in the UK.
Can I use TV or satellite coax for a CB radio?
No. The Belden 9116 datasheet describes Series 6 broadband coax for cable television, RF drop and over the air aerials, with a nominal characteristic impedance of 75 ohms. Your radio, meter and antenna are 50 ohm devices, and a TV or satellite downlead ends in a Belling-Lee or F connector, neither of which mates with an SO239.
CB coax cable types compared: RG58, Mini8 and RG213
These are the published specifications from our own product pages. Every loss figure is quoted at 100 MHz, which matters below.
| Specification | RG58 | Mini8 | RG213 |
|---|---|---|---|
| Impedance | 50 ohms | 50 ohms | 50 ohms |
| Outer size | 6mm | 7mm | 9mm (9.65mm) |
| Core | 19 x 0.18mm | 19 x 0.28mm | 7 x 0.72mm |
| Braid coverage | 89%, 120 x 0.10 | 88%, 128 x 0.12 | 98%, 192 x 0.20 |
| Loss per 10m at 100 MHz | 1.5 dB | 1.2 dB | 0.7 dB |
Read the braid row carefully. At 89% against 88%, Mini8 buys no screening over RG58. It buys a thicker centre conductor, 19 x 0.28mm against 19 x 0.18mm, and the lower loss that follows. The step change in screening is RG213 at 98%.
Loss over length, and what those decibel figures mean
Loss scales with length, so multiply. Derived from the quoted per 10 metre figures, a 20 metre run at 100 MHz costs about 3.0 dB in RG58, about 2.4 dB in Mini8 and about 1.4 dB in RG213.
Now the honest part. UK CB sits at 27 MHz, not 100 MHz, and coax loss falls with frequency, so a real CB run loses less than the headline figure. Belden quote their 8262 RG-58 at 1.4 dB per 100 ft at 10 MHz, 3.3 dB at 50 MHz and 4.9 dB at 100 MHz, so 27 MHz sits between the first two rows. Their 8267 RG-213 follows the same shape, 0.55 dB at 10 MHz against 1.9 dB at 100 MHz. Different cables from ours, so rank grades with them, do not predict channel 19 from them.
Best coax cable for a mobile CB install
Mobile runs are short. Where a mount or antenna here comes with cable, it is typically 3.6 to 4.5 metres of RG58, PL259 fitted: 3.6 metres on the Sirio Mag 145 PL, 4 metres on several magnetic mounts, 4.5 metres on the Santiago 600. Over that distance the earth, the mount and a clean plug matter more than grade. For siting, see our guide on choosing a CB antenna for a vehicle.
Best coax cable for a CB base station
A base run is often ten to thirty metres, outdoors for years, and that is where RG213 earns its cost. Ours is described as a low loss, 50 ohm, MIL spec cable, suited to outdoor use for its UV resistance and direct bury durability, and to high power amateur stations on long runs. Ready made RG213 leads, PL259 both ends, are listed at 10, 20 and 30 metres, to pair with a home base antenna.
When a thicker cable is worth it
Thickness buys lower loss and far higher power handling, and costs routing flexibility. Belden rate their 8262 RG-58 at 300 W at 50 MHz and 200 W at 100 MHz, against 1,122 W and 748 W for the 8267 RG-213. As a rule of thumb, under about five metres the grade barely shows; over fifteen metres it shows on every call.
PL259 fitting, and the SO239 side
RG213 takes the standard 9mm PL259 body, and N-Type, as its product page states. Thinner RG58 and Mini8, at 6mm and 7mm, need a plug matched to their diameter, normally a PL259 with a reducer, or the braid will not clamp and the joint fails when the cable flexes. Soldering one well means tinning the braid through the side holes without cooking the dielectric.
Routing the cable so it survives
Respect the bend radius. Belden publish an installation minimum of 2 in (51 mm) for their RG-58 and 4 in (100 mm) for their RG-213, and forcing a cable tighter deforms the dielectric. Keep it clear of hinge pinch points and exhaust heat, and add a drip loop so water runs off before a connector. Where a mount leaves no room, an angled connector with two SO239 sockets, specified DC to 600 MHz with a 16 mm mounting hole, lets the cable leave sideways.
How to fix a CB coax cable
Diagnose before you cut. Our SWR guide lists a bad or loose coax connector and a damaged coax cable among the common causes of a high reading, so the feeder is a fair suspect.
- Substitute a known good short lead. A half metre RG58 patch lead with PL259 on both ends is the ideal test piece, and stays useful for CB, marine and PMR work.
- Flex the cable near each plug while watching the meter. A reading that jumps points at the termination.
- Inspect where it passes a seal, a hinge or a sharp edge, looking for flattening, cuts or corrosion.
A crushed or badly terminated cable can push an SWR reading up, so rule the feeder out before shortening a whip. See what SWR is and how to tune a CB antenna. Then either re-terminate properly or replace the lead.
Dual coax and co-phased antennas
Some trucker antennas are designed to work either singly or as a twin co-phased pair, and the Sirio Bull Trucker 5000 specification says exactly that. Follow the maker’s own phasing harness instructions: the pair only behaves as intended when the feed is built as specified.
Scanner, VHF and UHF runs
Loss climbs with frequency. The same 8262 RG-58 that loses 1.4 dB per 100 ft at 10 MHz loses 7.3 dB at 200 MHz and 11.5 dB at 400 MHz. A cable that is fine at 27 MHz works far harder up there, so on a long run to a rooftop scanner or VHF antenna, step up in size.
Short list by setup
- Short mobile run. The RG58 supplied with the mount.
- Medium home run, sheltered. A ready made RG58 lead at 10 or 20 metres, or a Mini8 reel.
- Long or outdoor home run. RG213, for the UV resistance, the 98% braid and the lowest loss.
Frequently asked questions
What coax cable should I use for a CB radio?
Use 50 ohm coax with PL259 plugs. In a vehicle, the 3.6 to 4.5 metres of RG58 supplied with a mount or antenna is fine. For a base run of 10 metres or more, RG213 is quoted at 0.7 dB per 10 metres at 100 MHz against 1.5 dB for RG58, so it suits the distance.
Can I use TV coax cable for a CB radio?
No. Broadband and cable television coax is 75 ohm, built for CATV, RF drop and aerial use, as the Belden 9116 datasheet states. Your radio, antenna and SWR meter are all 50 ohm, and a TV or satellite downlead ends in a Belling-Lee or F connector rather than the PL259 a CB set requires.
What is the best coax cable for a CB base station?
RG213 for most home installs. Its product page describes a low loss, 50 ohm, MIL spec cable with UV resistance and direct bury durability, suited to long runs at high power, and it takes standard 9mm PL259 and N-Type connectors. Ready made RG213 leads are listed at 10, 20 and 30 metres.
How do I fix a CB coax cable?
Test before cutting. Substitute a known good half metre patch lead, flex the suspect cable near each plug while watching the SWR meter, then inspect where it passes seals and hinges. A bad or loose connector and a damaged cable are both listed as common causes of high SWR.
What connector does CB coax use?
A PL259 plug, which screws into the SO239 socket on the radio, the mount or the antenna. Our RG213 takes the standard 9mm PL259 body, while 6mm RG58 and 7mm Mini8 need a plug matched to their diameter. Factory leads arrive with the PL259 soldered on each end.
Unsure which run you need? The coax cable category lists reels and ready made leads. We are in Larbert, Falkirk, with UK wide courier delivery.