Part of our Building Your First Ham Radio Station guide.
Coax is easy to treat as an afterthought. It is just the cable between the radio and the antenna, right? But the type and length of coax you run has a real effect on how much of your power reaches the antenna, how much you spend, and how convenient your station is to work with. Here is a practical look at choosing coax for HF.
Why coax loss matters
Every foot of coax has some loss, meaning a bit of your transmit power turns into heat in the cable instead of reaching the antenna, and incoming signals are slightly weakened on the way to your radio. Loss is measured in decibels (dB) per 100 feet, and it depends on three things: the type of coax, the length of the run, and the frequency. Loss goes up as frequency goes up, so the same cable that is fine on HF may be lossy at VHF or UHF.
The good news for HF operators is that HF frequencies (roughly 1.8 to 30 MHz) are relatively forgiving. Loss is low enough that on short runs, the difference between cable types barely matters. On long runs, it starts to matter a lot.
Common coax types for HF
- RG-58 is thin, cheap, and flexible, with relatively high loss. Fine for short jumpers and portable use where a few feet will not hurt you.
- RG-8X (mini-8) is a middle-ground cable: thicker than RG-58, still fairly flexible, lower loss. A popular choice for portable operating and moderate runs.
- RG-213 and RG-8 are thicker, lower-loss cables good for longer runs at a home station. Less flexible and heavier, but efficient.
- LMR-400 (and similar) is a low-loss cable prized for long runs and higher frequencies. It is stiff and pricier, but it delivers excellent efficiency.
- RG-174 is very thin and lossy, used mainly for very short connections inside equipment or tiny portable setups.
How length changes the picture
Since loss is per unit length, the length of your run is the single biggest factor in whether coax choice matters. Here is how it plays out across the range you asked about, on HF:
- 3 to 15 feet: Almost anything works. Even lossy cable like RG-58 gives up only a tiny fraction of a dB at HF over these lengths. For a short jumper or a portable setup, pick whatever is flexible and convenient. Do not overspend here.
- 25 to 50 feet: Now the differences start to show, though they are still modest on HF. RG-8X is a sensible, economical pick for this range. RG-58 is usable but you are leaving a little on the table, especially toward the top of HF.
- 50 to 100 feet: This is where good coax pays off. Over 100 feet, a thin cable like RG-58 can waste a meaningful chunk of your power, while RG-213 or LMR-400 keeps loss low. If you have a long run to a tower or a far corner of the yard, invest in lower-loss cable.
A useful way to think about it: a fraction of a dB is inaudible and not worth worrying about, but once you are losing 1 to 3 dB or more in the feedline, you are throwing away a noticeable portion of both your transmit power and your received signals.
Cost versus benefit
Better coax costs more, is thicker, heavier, and less flexible, and uses bulkier connectors. So the goal is not always the lowest-loss cable, it is the right cable for the job:
- For short runs and portable work, favor flexibility and low cost. RG-8X or even RG-58 is perfectly reasonable, and the weight savings matter when you are carrying it.
- For permanent home runs, especially long ones, favor low loss. RG-213 or LMR-400 is worth the extra money because you install it once and benefit every time you transmit.
- If you also operate VHF/UHF on the same feedline, lean toward lower-loss cable, since loss climbs quickly at higher frequencies.
A few other things to keep in mind
- Connectors and weatherproofing matter. A great cable with a corroded connector or water intrusion will perform poorly. Seal outdoor connections well.
- Quality varies. There is a lot of cheap, mislabeled coax out there. Buy from reputable sources so you actually get the specs on the label.
- Do not buy more length than you need. Extra coiled-up coax just adds loss. Run what you need with a little slack, not a huge excess.
The short version: on HF, keep short runs cheap and flexible, and spend your money on low-loss cable only when your runs get long. Match the coax to the job and you will get efficient performance without overpaying or wrestling with stiff cable you did not need.