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The Industrial Wi-Fi Shop Podcast – Ep. 11 Cable Guy!

66 min • 6 november 2024

Contact the guys at the Industrial Wi-Fi Shop!
Scott – [email protected]
Jeremy – [email protected]

R-Coax Deep Dive

High Level

What is Radiating Cable? Is it “Wire for a wireless system?” Let’s dig in.

Leaky Coax is an extruded copper core, with an external copper sheath. Featuring slits along one side which allow RF to escape (the matrix).

It is composed of just four components. An inner conductor, a dielectric or low density PE layer, an outer conductor with slots, and a cable jacket. This technology has been around for 40-50 years from what I can tell.

The slits allow emission of certain frequencies.

It goes by several names, but most commonly referred to (by me) as leaky coax. You may have heard of:

Radiant Coax
Radiating Cable
Leaky Coax
Leaky Feeder
RCoax
<expletive deleted>

The standard boiler plate use cases are AGV systems, overhead cranes, rotating machinery, skillet systems, monorails, mining, even tunnels in some cellular applications. We deploy it in these scenarios and also entertainment applications.

This stuff is a pain to get in, stiff and easy to damage if you aren’t careful. Siemens documentation says it has a spatially limited radio link, but the stuff can be detected up to 30 meters away if using enough power from the radio.

The main benefit is that it replaces things like slip rings where constant flexing of ethernet cables leads to wear and failure.

RF Propagation

This can work in 2.4GHz, 5GHz and also the new 1.21 Gigawatts band they teased for release in early 2025

Think about it kinda like one of this perforated garden hoses, a little water comes out at every inch of the cable.

I call it the astropop, essentially at the head end, where the most energy comes out it’s the broad base of a cone and tapers to the end of the cable.

Near field 2-10 cm

Far Field: 0 to 3M

Typical loss (approximate) per 100m 17dbm for 2.4 and 27 for 5GHz

Segment length reduces transmission rate.

Installation

There is a ridge on the back side of the transmission surface, which is used to align the cable. Make sure your antenna is on the side of the remote antenna.

Not intended to be mounted directly to surfaces, requires standoffs with a minimum of about 5cm.

Secure with a clip at least every meter. There are metal reinforced clips available for more secure mounting and can be interspersed every 10 meters. YMMV

DO NOT MOUNT CLOSE TO BUS BARS!!!

A 480 bus bar is an electrical connection point that distributes and transports electricity.

SHOEs or Induction of current. Think of a trolley.

<— Wanna hear about how I got shocked?

Some radio vendors recommend overlap, some don’t.

Can be installed outdoors. If it is in danger of being stepped on you can protect with something like cable tray. <— Picked this tip up from some smart guys on a carousel installation

A hacksaw file and a few wrenches is all you really need to put the N-Type connectors on the end. Don’t use snips.

You can also use rubber pipe wrenches to help grip for twisting the cable as you lay it or fix misalignments.

Best Practices

Keep the antenna within 1” to 2 meters, you can get away with a longer distance though. The signal will degrade the further you get away from the cable. If you can reach out and touch the coax, you should be good to go.

Don’t put it in channels.

Check the alignment with the ridge, then check it again every few weeks after initial install make sure it settles into the installation. This stuff will relax after some time.

Don’t get shocked, or do, but don’t say I didn’t warn you. Keep it the minimum distance from high voltage rails.

Keep the remote antenna in line with the central axis of the EM field.

Mind the bend radius.

Torque stripe the cable at the clips for easy visual inspection. Do this after the cable has settled.

Don’t install the radio in EX zones (Class1, Div 2 – explosive zones),

cable is passive so treat it like an antenna

Be mindful of common outdoor, corrosive environments and follow the same component sealing best practices.

Not sure about direct burial of this stuff, but it might work.

Typically we only use this as SISO, though it appears ProSoft will allow you to install using two tx chains.

You can dual feed and use something like a UNII-1 and UNII-2 channel to send signals from both ends.

This is an exotic application so be wary of the hardware you use.

Angling antennas slightly improves performance.

Fun Stuff

My most famous project and probably the only one I can talk about with much detail is the Secret Life of Pets ride in Universal Studios Hollywood. Got it in right before Covid locked everything down.

We won an award for this ride.

It is what is referred to as an omni mover. The cable is installed inside the machine guarding and has tons of bends and turns in it.

A few takeaways, not all unions are the same, which is fun. I learned about the delicate nature of sitting around waiting on someone who has no idea what they are doing install hardware while I scream internally. Mostly good people, so don’t take this as a total knock against union workers.

We made some on the fly brackets after the custom client brackets we built hit some stuff in line of travel which wasn’t supposed to be there. Amazing what you can do with bar stock, a bench vise, a step bit, and a hammer.

We got to figure out how to make the Fluidmesh radios work with this cable. So that was fun.

Acceltex Clear Antennas