Coax for Amateur Radio: RG58, RG213, LL240 and LL400 Compared

 Most people don't think about their feedline until the signal report comes back weaker than it should.

A while back, a fairly typical cable question came up: a customer needed coax for an antenna installation, knew the length of the run, and had already decided on RG58 because it was cheaper and easier to handle. The run wasn't particularly short, though. It was heading from the radio room towards an antenna well away from the shack.

On the reel, RG58 looked like coax. It had the right connectors available, it was 50 ohm, it was flexible and it was considerably cheaper than the heavier options.

So what's the problem?

Nothing, if the job is right for RG58.

That's the bit that catches people. RG58 isn't a bad cable. RG213 isn't automatically better for every installation. LL240 and LL400 aren't magic signal boosters either. They're different feedline choices, and the sensible choice depends on what you're trying to do with them.

The mistake is treating all coaxial cable as interchangeable because it carries the same basic job.

In radio, the feedline is part of the RF system. Ignore it and you can end up spending money on a better radio or antenna while quietly throwing away performance in the cable between them.

Where Most Cable Choices Quietly Go Wrong

The way people usually shop for coax is surprisingly simple: they know how many metres they need, then they look at the price.

"How much for twenty metres?"

That's often the first question. Not attenuation. Not operating frequency. Not the environment. Just length and price.

And that's understandable. Nobody wants to spend twice as much on cable if they don't need to.

But a ten-metre run and a fifty-metre run aren't really the same cable job, even if both are described as "coax for antenna".

Frequency matters too. A cable loss that seems tolerable at one frequency can become much more noticeable higher up the VHF and UHF bands. As frequency rises, attenuation generally increases. Add more cable and you increase the total loss again.

That means the right 50 ohm coaxial cable is not simply the one that physically reaches the antenna.

It's the one that does the job without giving away an unnecessary chunk of the signal along the way.

This is why four cable types that look like variations on the same theme can make quite different sense in an amateur radio installation: RG58, RG213, LL240 and LL400.

RG58 Is Fine for a Lot of Jobs

RG58 cable has been around radio equipment for a very long time, and for good reason.

It's relatively thin, flexible and easy to route. If you've got a short patch lead, a bench setup, a mobile installation, or a modest antenna run where the losses are acceptable, RG58 can be perfectly sensible.

It's also convenient when you're working around equipment where a thick, stiff feedline would be more trouble than it's worth.

The problem starts when people take those advantages and assume they make RG58 suitable for everything.

They don't.

A long RG58 run can introduce considerably more attenuation than a lower-loss cable designed for the same sort of application. You may still hear stations. You may still make contacts. Your transmitter may still show a sensible SWR.

And that's where it gets sneaky.

A radio system can "work" while losing useful RF in the feedline.

One troubleshooting job illustrates this nicely. A station had a weak signal that was initially suspected to be a radio or antenna problem. The equipment itself checked out. The antenna wasn't obviously damaged. SWR wasn't giving anyone a reason to panic.

The feedline, however, was a long run of relatively thin coax that wasn't a good match for the installation.

There wasn't a dramatic failure. Nothing had gone completely open circuit. The radio simply wasn't getting the benefit of the signal it could have had.

That's one of the frustrating things about coax cable loss: it doesn't always announce itself.

Why Longer Runs Change Everything

Think about the feedline as a toll road for RF. Every metre takes a little something, and the amount taken depends on the cable and the frequency.

The longer the cable run, the more those losses accumulate.

Suppose you've got a short run from a radio to an antenna mounted nearby. The convenience and flexibility of RG58 may outweigh the extra loss. There's not much cable there in the first place.

Now move that antenna to a mast or tower and suddenly the cable run is several times longer. Add VHF or UHF operation and the decision deserves more attention.

This is where RG213 starts to make sense for many base-station installations.

RG213 is physically larger than RG58, with a thicker construction and generally lower attenuation. It's also less flexible and takes up more room when you're routing it through a wall, conduit or equipment rack. You need to allow for that.

But if you've got a meaningful run from the shack to an outdoor antenna, the reduction in feedline loss can be worth the extra cable size and cost.

Then there are low-loss options such as LL240 and LL400.

These are the sort of cables that become interesting when the cable run is long, the operating frequency is higher, or both. The point isn't simply that they're "better". The point is that lower-loss coax can preserve more of the RF you're paying for with every watt from the transmitter.

That's particularly relevant when you're working with VHF and UHF systems, where cable attenuation deserves serious attention.

A useful way to think about the comparison is this:

RG58: convenient, flexible and useful for shorter runs and less demanding installations.

RG213: thicker, more robust and generally a better choice when you need lower loss over a longer base-station run.

LL240: a low-loss option that can be attractive where performance and cable size need to be balanced.

LL400: a larger low-loss cable suited to installations where keeping feedline attenuation down is a priority.

The exact attenuation figures should always be checked against the manufacturer's specifications for the particular cable. Don't buy a cable based on its name alone. Construction and specification can vary between products, and the frequency you're operating at matters.

The Cable Looked Fine on the Reel

Here's another mistake that happens more often than people like to admit.

The cable looks perfect when it's new.

It's clean. The jacket is intact. It bends nicely. The connectors go on. You run an SWR check and everything appears reasonable.

Then it spends a year outside.

Australian weather isn't especially forgiving to equipment that wasn't intended for prolonged outdoor exposure. UV, heat, moisture and mechanical movement can all take their toll. A cable running up a mast or across a roof isn't sitting in a nice indoor equipment cabinet.

I've seen installations where the cable looked perfectly respectable from the ground, while closer inspection showed the outer jacket had deteriorated. Once moisture gets where it shouldn't, the original electrical performance can change.

This is why outdoor-rated coax matters.

And the cable itself isn't the only concern. The connection at the antenna deserves just as much attention. A good feedline with a poorly weatherproofed connector is still a problem waiting to happen.

Marine installations make this even more obvious. A marine antenna cable can be exposed to salt air, movement, spray and constant changes in temperature. The cable needs to suit that environment, and the connection needs to be protected properly.

There is a tendency to think of weatherproofing as the finishing touch.

It isn't. It's part of the installation.

Cheap Coax Usually Comes With Expensive Signal Loss

There's nothing wrong with looking for value. Radio equipment isn't cheap, and nobody wants to waste money.

But bargain coax can be a false economy.

Sometimes a cheap cable will measure close enough to what you expected when it's new. The trouble is that the installation isn't happening in a laboratory. It's going outdoors, around corners, through penetrations, onto connectors and, in some cases, up a mast where you really don't want to replace it next month.

Cable thickness matters because it affects how the cable is constructed, how it handles mechanically and, in many designs, how much loss you can expect. Flexibility matters too. A thick low-loss cable may perform brilliantly but be awkward in an installation that requires tight routing.

This is where the idea of "best coax for long cable runs" needs a little qualification.

The best cable isn't necessarily the thickest cable you can afford.

It's the cable whose loss, construction, flexibility, environmental rating and connector compatibility suit the actual installation.

And yes, connectors matter.

There's not much value in buying a good low-loss feedline and then fitting unsuitable or poorly installed connectors. The cable and connector system needs to be considered together. A bad termination can introduce losses or reliability problems of its own.

When RG213 Makes More Sense Than RG58

RG213 is often the natural step up when an operator looks at a longer base-station feedline and realises that RG58 isn't necessarily the economical choice in the long run.

It's thicker and less flexible, so you need to plan the installation accordingly.

But that extra bulk isn't there for decoration.

For a longer HF or VHF installation, a lower-loss feedline can make a worthwhile difference. At VHF and UHF especially, the cumulative effect of cable attenuation can become significant.

Imagine spending money and time putting an antenna at a better height, only to run a long length of higher-loss cable back to the radio.

The antenna is doing its job.

The feedline is quietly taking some of the benefit away.

RG213 is not always the answer, but it's a cable worth considering when the run length makes loss more important and the physical size isn't a problem.

LL240 and LL400: When Low Loss Becomes the Priority

LL240 and LL400 sit further towards the low-loss end of the conversation.

These cables are particularly relevant to operators and installers who have longer runs to deal with or who are working at frequencies where feedline loss becomes increasingly important.

The physical difference is noticeable. LL400, in particular, is a substantial cable compared with RG58. That's both an advantage and an installation consideration.

You can't always route a large low-loss cable wherever you can route a thin flexible one.

You may need larger bends, stronger support and more thought around connectors and entry points. That's not a reason to avoid it. It's simply part of specifying the installation properly.

One old-timer at a radio club I know puts the general idea rather bluntly: if you've already gone to the trouble of putting the antenna in the right place, don't casually throw away the improvement with an undersized feedline.

That's a fair way of looking at it.

LL240 can be a useful middle ground where you want better loss performance without going all the way to a very large cable. LL400 makes more sense when minimising feedline loss is worth accommodating the extra diameter and stiffness.

Again, check the actual manufacturer's attenuation specifications at your operating frequencies. "Low loss" is useful terminology, but the numbers are what let you compare cables properly.

The Frequency You Use Changes the Conversation

Someone running HF doesn't necessarily have the same cable priorities as someone running a UHF station.

That's because coax cable loss is frequency dependent.

At lower frequencies and shorter cable runs, the loss may be modest enough that a flexible cable such as RG58 is perfectly reasonable.

Move up into VHF or UHF, increase the cable run length and suddenly the feedline deserves more attention.

This is why there isn't one universal answer to "which coax should I buy?"

A short amateur radio coax run might be a simple decision.

A long run to a rooftop or tower isn't.

You need to know the approximate frequency, the total cable run length and where the cable will live. If the cable is going outside, include the environmental conditions. If it has to make difficult bends, consider flexibility. If you're fitting connectors yourself, make sure the cable and connector are compatible.

It sounds like a lot of detail.

In practice, it's five minutes of thinking before you buy instead of five hours of troubleshooting later.

The Failed Installation Nobody Wants to Repeat

One particularly annoying installation mistake is underestimating the actual cable run.

Someone measures the straight-line distance from the radio to the antenna and orders that much cable.

Then the cable has to go around a room, along a wall, through a penetration, up the mast and leave enough slack for proper routing and servicing.

Suddenly the "twenty-metre run" isn't twenty metres.

It's thirty-five.

Or forty.

And if you've already bought a cable that was marginal for twenty metres, you've just made the situation worse.

A little spare length is sensible. Excessive cable coiled into a tight bundle isn't a substitute for planning either.

Measure the real route.

Then add a sensible allowance for routing, connectors and future maintenance.

That small bit of planning is much cheaper than re-running cable after the installation is finished.

Buying Coax Before You Climb the Mast

This is probably the most useful habit you can develop.

Work out the cable run before you start installing the antenna.

Not approximately. Properly.

Walk the route. Allow for the vertical rise, horizontal distance, bends and entry point. Think about where the cable needs to be supported and where it will terminate.

Then look at the expected attenuation for the cable at your operating frequency.

If you're running HF over a relatively short distance, RG58 may be all you need.

If you're running a longer base-station feedline, RG213 may make more sense.

If you're dealing with a long VHF or UHF run where cable loss is becoming a major consideration, LL240 or LL400 may be worth the additional cost and installation effort.

There is no prize for using the thickest coax on the shelf.

There's also no prize for saving a few dollars on cable and then spending an afternoon back on the roof trying to work out why the station isn't performing as expected.

Getting the Cable and Connectors Right Together

A coax cable comparison isn't complete without mentioning terminations.

The connector needs to suit the cable and the equipment. The installation needs to be mechanically sound. Outdoor connections need appropriate weather protection.

It's easy to concentrate on the cable specification because that's what appears on the product label.

But an RF installation is a chain.

Radio, connector, feedline, connector, antenna.

A weakness anywhere along that chain can become the problem you end up chasing.

And chasing RF faults can be surprisingly time-consuming because the symptoms aren't always obvious. A poor connection might look like a radio problem. Feedline loss might look like an antenna problem. Water ingress might look like an intermittent fault that appears only under certain weather conditions.

This is where good installation practice saves more money than buying the cheapest cable.

So, Where Do You Start?

If you're unsure which cable suits a particular antenna installation, start with three things: frequency, cable run length and environment.

Then look at attenuation.

For a short indoor connection, flexibility and convenience can be more important than squeezing out the last fraction of a dB.

For a long outdoor run, especially at VHF or UHF, low-loss coax becomes much more attractive.

If the cable is going outside, choose something appropriate for the environment and protect the connections properly.

And don't forget that cable routing itself matters. Don't crush the coax, don't force tight bends where the cable isn't designed for them, and don't leave a heavy cable hanging from a connector at the antenna.

If you're ready to compare what's available, you can browse Comtek Radio's coaxial cable range and match the cable to the installation rather than simply buying the cheapest option by the metre.

That's really the whole point.

RG58, RG213, LL240 and LL400 aren't competing for one universal title. They're tools for different jobs.

RG58 is handy when you need a flexible, practical cable for a suitable short run. RG213 gives you a more substantial feedline when lower loss and longer runs matter. LL240 and LL400 come into their own when preserving RF over longer or higher-frequency runs becomes a priority.

The expensive mistake isn't necessarily buying the more expensive cable.

It's buying the wrong one, installing it somewhere awkward, weatherproofing it, connecting everything up... and then discovering that the feedline was the part of the system quietly costing you performance all along.

Most weak-signal complaints aren't dramatic. They're just a feedline that was never quite right for the run.