Two 433MHz based systems in same environment?

Can two 433MHz based systems co-exist in the same environment? Or does the mere fact that they share the same frequency space make it not practical? (i.e. they would interfere with one another etc.)

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It depends what behaviors are forced on each of these systems by the regulations applicable to their type approval. But in general the answer is yes, they can share the same space. Often found, for instance, in wireless alarm systems (in Europe).

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Having first taken the post to mean to 433MHz clocked processors side-by-side I now see what is going on! Presumably they can't both transmit at the same time without interfering so some kind of arbitration would be required?

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Tom Lucas

On Sep 17, 7:43 am, "Tom Lucas"

Yeah, me too, until I realized what frequency he was talking about :)

No. Most systems use very infrequent, redundant messages and random timing to avoid the need for any kind of master arbitrator. For cost reasons such systems are usually one-way.

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The last time I looked at 433 there seemed to be a requirement that transmitters had to have a 1% or less duty cycle, that is with a wideband 433 signal. There are new 433 band devices which are narrow band, and there are up to 36 NBFM channels available, and can have a 100% Tx time


Reply to
Martin Griffith

In the UK at least, the maximum allowed duty cycle depends on the exact

433MHz sub-band, channel bandwidth and radiated power. The details are in IR 2030 if anyone is interested. (Make sure that you pick up a relatively recent edition; it's been revised within the last year or so.)


Simon Clubley,
Microsoft: Bringing you 1980's technology to a 21st century world
Reply to
Simon Clubley

I would not put any critical applications on the 433 MHz ISM band, since amateur radio is the primary allocation with 100-1000 W transmitted power, while the license free ISM (Industrial, Scientific, Medical) operations are in the 10 mW-100 mW range.

If you have a radio amateur operator at 100 m, you might get 1 m communication distance with some license free LowPower-device.


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Paul Keinanen

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