Your feedline is the quiet part of the antenna system. It carries power from the radio to the antenna, and every choice you make about it affects how much of that power actually gets radiated. Most hams start with coax because it is convenient, but open-wire and ladder line have been used for a very long time for good reasons. This guide compares them so you can match the feedline to your antenna and your situation.
Two Very Different Kinds of Line
Coaxial cable has a centre conductor surrounded by insulation and an outer shield. The fields stay inside the cable, which is why coax is so easy to live with. Ladder line, also called window line or open-wire line, is two parallel conductors held apart by plastic or spreaders. It is a balanced line: the two conductors carry equal and opposite currents, and it relies on that balance to keep its fields from radiating.
Impedance: The Number That Drives the Decision
Amateur transceivers are designed to work into about 50 ohms, and the most common coax has a characteristic impedance of 50 ohms. Ladder line is usually somewhere in the range of 300 to 600 ohms, depending on wire spacing. A resonant half-wave dipole fed at the centre presents an impedance in the neighbourhood of tens of ohms, so it pairs naturally with coax. The same wire used on several bands presents very different impedances on each one, and that is where ladder line comes in.
Loss: Where the Power Goes
All feedlines lose some power as heat. For coax, loss rises with frequency, rises with length, and is higher in thinner cable. It also rises when the SWR is high, because the reflected power travels back and forth along the line and is attenuated on each pass. Ladder line has very low loss even when it is carrying a high SWR, because its conductors are large relative to their spacing and there is little dielectric material. That is why it is popular with multiband doublets and with long runs on lower HF bands.
Two practical points follow. On a matched, single-band antenna with a short run, the difference between good coax and ladder line is often small. On a multiband antenna with a poor match on some bands, the coax can lose a lot more.
Where Ladder Line Shines
- A centre-fed doublet or other wire antenna used on many bands with a tuner.
- Antennas on bands where the feedpoint impedance is far from 50 ohms.
- Longer runs where coax loss would add up, especially at higher HF frequencies.
- Low-cost installations where a lightweight, low-loss line is an advantage.
If you are still choosing an antenna, the beginner's decision guide to a first HF antenna pairs well with this article.
Where Coax Wins
Coax is forgiving about where you put it. You can run it along a metal mast, tape it to a tower leg, bury a suitable direct-burial type, or route it through a wall without much thought. It is shielded, so it is less prone to picking up noise from household electronics and less prone to radiating into your own shack. It is also the standard for beams, verticals, and most commercial antennas, which are designed for 50 ohms. If your antenna is resonant and matched, coax is usually the simplest choice.
Balanced Line Meets an Unbalanced Radio
Your transceiver has an unbalanced coax output, while ladder line is balanced. You need something to bridge the two, either a balanced antenna tuner or an unbalanced tuner followed by a balun. Choose a balun or tuner rated for the power and for the wide range of impedances it will see, because some baluns can overheat with a large mismatch. This is one reason to read the specifications carefully instead of assuming any balun will work in every situation.
The same principle applies on the coax side. A dipole fed with coax is also a balanced antenna on an unbalanced line, so a balun or common-mode choke near the feedpoint helps keep current from flowing on the outside of the shield and radiating.
Installing Ladder Line Properly
- Keep it away from metal such as gutters, siding, and mast sections. A few inches is a minimum and more is better.
- Bring it away from the antenna at a right angle for a short distance before turning.
- Use standoffs or insulators so it does not touch walls or tree branches, and leave a little slack so wind does not strain the connections.
- Avoid tight bends and never coil it up in a pile, which upsets the balance.
- Use a proper window or feedthrough panel to enter the building, and keep the last stretch of line away from metal objects.
- Connect it at the shack to a balanced tuner or a suitable balun.
Window line can be affected by rain, ice or snow, which changes its impedance and adds some loss. Open-wire line with wide spacing handles weather better.
Installing Coax Properly
Use a cable suited to your bands and run length. Thicker cable generally has lower loss but is heavier and stiffer. Fit connectors carefully, since a poor connection is a common source of noise and intermittent problems. Seal outdoor connections with self-amalgamating tape or a similar weather seal, and leave a drip loop so water does not run into the shack. Follow local electrical codes for grounding and lightning protection, and disconnect and ground outdoor lines when an antenna is not in use during storms.
Common Mistakes
- Running ladder line tightly alongside a metal pole for its whole length.
- Using a cheap or undersized balun with a high-SWR antenna.
- Choosing very thin coax for a long run on higher bands.
- Skipping a choke on a coax-fed dipole and then wondering why the shack picks up RF.
- Trusting the tuner to hide a poor feedline; a tuner can present a good match to the radio, but any loss in the line and in the tuner is still there.
- Guessing about conditions instead of checking them. A quick look at the live HF propagation page tells you which bands are worth testing first.
Safety and Licensing
Ladder line at high SWR can carry high RF voltages, particularly at the antenna end and at the point where it meets the tuner. Keep it out of reach of people and pets, keep it clear of anything a person can touch, and never work on a feedline while transmitting. Keep every antenna and feedline well away from overhead power lines, and follow the manufacturer's guidance for any device you use. Transmitting requires the right licence, and the rules on power, bands and station operation differ between Canada and the USA, so check your own regulator's current rules. If you are still studying, the licence exam practice is a good place to build confidence.
A Simple Way to Choose
If you have a resonant single-band antenna or a beam, use coax. If you have a multiband wire antenna and a tuner, ladder line is usually the better feedline, as long as you can route it cleanly. If your setup is limited by space, weather or nearby metal, coax may be the more practical choice even if it loses a bit more. A good middle path is to use a thick, low-loss coax with a balun at the feedpoint and see how the antenna works before you change it. The simple half-wave dipole guide is a good place to start experimenting.
Wrap-Up
Neither feedline is better in every situation. Coax gives you shielding, simplicity and tolerance for where you route it, while ladder line gives you very low loss with mismatched multiband antennas, provided you handle balance and spacing carefully. Note which combination you use and how it performs, and keep those notes with your contacts in the free online logbook so you can learn from real results. If you need parts, the ham radio marketplace lists antennas and accessories.
How HamRadioList can help
Once your feedline is in place, the free HamRadioList logbook is a handy place to record which antenna and feedline you used for each contact, so you can compare results over time. Check the live HF propagation page before you call CQ, and browse the marketplace if you need coax, connectors or a balun.
- Live HF propagation - see current band conditions before you call CQ.
- Free online ham radio logbook - log every contact, import and export ADIF, sync with QRZ.com and keep your awards organised.
- Ham radio marketplace - buy and sell radios, antennas and accessories.
- Ham radio FAQ - plain answers to the questions new operators ask most.
- Ham radio quick reference - bands, modes, phonetics and Q-codes on one page.
New here, or getting back on the air? Create your free HamRadioList account to log contacts, check band conditions and practise for your exam, or browse more guides from the blog. HamRadioList is built by amateur radio operators in Nova Scotia for operators everywhere.