A question for the real nerds who know about wireless comms

[The Artist]

I need to transmit an important N/C or N/O signal, think machinery commands and emergency stop type stuff, 2km with line of sight in Europe.

Must be legal
Unlimited power is available.
Must be reliable and not give false signals.

Any ideas?

I see 900Mhz E-stop systems available but they are not legal in Europe as that frequency is used for telecoms.

433MHz is limited in range due to power limits.

Wifi way too short.

[MCN]

Twisted Pairs.

Sorry, I'm no help.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Robby]

I've been around a few sites doing thing that are important.

Over that distance it would be a cabled connection.

Longer distance could be a microwave link, but these days more likely to be a phone line. Sometimes an old fashioned twisted pair plugged into a 56k modem, nowadays more likely broadband.

From memory, all of the safety of life stuff relied on hard wiring and some kind of industrial protocol running over the wire. I can't remember any emergency stops running over that sort of distance, they were usually within seeing and shouting distance.

[Easy-X]

433 probably would work with directional antennas but not something I'd stake my life on. You probably need something industrial e.g.

https://www.racom.eu/eng/products/radio-modem-ripex-overview
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[WD Forte]

Lasers

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fwww.gadgety.co.il%2Fwp-content%2Fthemes%2Fmain%2Fthumbs%2F2019%2F01%2Flaser-dr-evil-1.gif&f=1&nofb=1&ipt=4508c7c97a7396d3371749f13b6dc0e338ba2b86f07eb32ce30ba89f3a04b48e&ipo=images
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bikers smell of wee

[WD Forte]

It sounds as if you only need to read two states, hi or lo for nc/no
can you run a cable? if so maybe put a repeater half way depending on the voltage levels and resistance/voltage drop of the cable.
The reciever circuit then only has to respond to a pre determined
high or low condition
Basically simple and no high frequency stuff required as that would suffer if high data rates were needed over that length of cable.

Or a fibre optic link with repeaters that run in an ON or OFF state
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bikers smell of wee

[The Artist]

[stinkwheel]

Presumably if it's safety critical, the signal should be constant and hold it in the "unsafe" state. Drop the signal for longer than a pre-determined period and default safe state ensues.

I'm not an expert but I immediately thought microwave too. Needs careful alignment though so how mobile are both ends?

A man at each end with a whistle, a red flag and a big red button?

I wonder if IR would have enough reach (giant TV remote)?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Easy-X]

[Robby]

Really we need more information on what you're trying to do.

You can get wifi antennas which claim impressive range, the directional parabolic ones claim up to 15km.

But the use case matters. If this is safety of life stuff, you go along to someone like schneider electric and buy an off-the-shelf solution and get it installed properly. If it's to control a water pump on a farm, you go cheaper.

[MCN]

Wireless or hard wired has to have certain redundancy built in.

I would not guess what protocol would suit without more info on the project.

It depends, as mentioned, on what the function is and how vital it is.

We still had those pipes that you shout into and listen to a horn on our drillship for comms between the control room at the front and the steering room at the back.

Although the four other systems were on UPS battery back up too.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[panrider_uk]

60GHz point to point wifi can do several kilometer distances if you have clear line of sight

eg
https://www.broadbandbuyer.com/products/46155-ubiquiti-wave-lr/

We use two pair of dishes to link our gatehouse to the admin building (the under road trunking carrying the fibre cable collapsed due to years of hgv traffic and was going to cost a fortune to re-instate)

The pairs automatically failover so if comms drop on one set then the other set kick in.
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Current bikes: Honda ST1100 Pan European. Moto Guzzi V85 TT Travel

[P.]