Wireless controls

[maltaron]

Is anyone else concerned with the amount of wireless remote control is around. Allthough the units have all sorts of encoding nothing is fool proof especially as a lot of this stuff comes out of China and other far east countries. I recently fitted a wireless energy monitor (Owl) and shortly after tunes were playing on my wireless doorbell, and it aint got tunes in it. I am concerned that a car key fob may disable a burglar alarm or worse affect a life saving device. I,m also concerned at the amount of RF energy around us, there are already concerns with mobile phones, and we now have many high power transmitters churning out multiplex digital signals which themselves are at radio frequency.

 

[sparkiedave]

And I joke with customers about taxis turning up when your cantral heating comes on

 

[electronicsuk]

I can appreciate your worries about interference between various wireless devices. However, what you experienced is most likely due to the very reason you've already stated yourself - a lot of this kit is manufactured in the far east, and clearly, little effort has gone into R&D in terms of interference mitigation.

It's more likely to be a fault in the design of the doorbell than anything else. The energy monitor has to transmit a data stream to the receiver, so there will (hopefully) be some basic error checking and addressing going on there to allow them to talk to each other. As the doorbell only requires an 'on' signal from the bell push, it probably just transmits that signal on a certain carrier frequency, with no validation at the receiver - ergo, anything operating on that frequency can cause the doorbell to go off.

Although bad design, it's not really a problem for insecure devices. The protocols used by wireless keyfobs for cars, alarms, garage door openers and the like are more secure. Admittedly it's not really my area of expertise, but I believe they rely on a system whereby a the receiving device stores a master cypher, which the user can then program into the transmitting devices they use with the system. As only the receiving and transmitting devices know the cypher, it is very difficult (but not impossible) for anyone to decrypt the signal over-the-air.

None of these should cause problems with life-saving devices (although I'm not sure to exactly what you're referring) if properly designed. What you're talking about now is Electro Magnetic Compatibility, which refers to the electromagnetic waves generated by almost all modern electronics, regardless of whether or not they intentionally incorporate any kind of transmitter. I believe EMC testing is a requirement to gain a CE mark, so most any device you buy in this country should be guaranteed to operate in harmony with other electrical devices around it.

Sometimes it's unavoidable that some spurious interference will be generated (like when using a mobile phone near a radio, or running a large motor), but manufacturers should make some effort to minimise the susceptibility of their products to electromagnetic interference, as well as to limit the generation of it. One would hope that medical devices would be properly shielded such as to prevent this kind of interference, given how commonplace it actually is.

I wouldn't worry yourself too much about digital TV signals. High power transmitters have been around us for a long time, but the truth is that at distance, the EIRP (that is, Effective Isotropic Radiated Power) is not very high at all, as the signal is spread out over such a large area. If this sort of thing does worry you then you should be far more concerned about using mobile phones, which can and do generated EIRPs in short bursts of up to 1 watt, and we're (well, most of us) quite happy to put them up against our head.

 

[ericmark]

I also get worried about the amount of gear that uses the shared 70cm band. And walking the dog while talking through the local 70cm and 2 meter repeaters to other radio amateurs I note with a chuckle how many security lights come on. And I am only using 3 watts. I hate to think what would happen if I was using the permitted 100 watts!

Best I heard of was a guy would take his misses to darts and while she was playing sit in the car talking on radio. At end of night guy in next car is playing heck with his misses for locking car and setting alarm with his keys still sitting in car. The lady takes out her key still in plastic wrapper you can guess what set the alarm.

But even low power it seems can cause problems, we found with ford transits locking one could also lock the next door truck although it would not unlock it again.

But really speaking it is surprising how little cross channel interference we do get. I have TV, DVD/Radio Player, DVD recorder, Sky satellite, Free to air satellite, and VCR and except where they are designed to work two devices we don't seem to have any problem using the 6 remote controls. OK light not RF but I would have expected some problems.

Some times it can be handy when my sister locks her car out side my sons house it works door bell with odd tune so he can hide quick?

Items designed for health and safety are normally OK. But using two way radios etc for crane control one have to follow fail safe. i.e. banksman talks load all the way down and loss of voice means driver stops rather than wait until in correct position and say stop. It will be the same with fire alarms if they lose signal then alarm goes off rather than send a signal to set off alarm.

Biggest problem is mobile phones as they pole. So unlike me with my radio when I press the button I see light go on so I know it was my radio with the phone even when not using it they pole to cell site every so often and not even a led to show they are transmitting. It took the nurse doing an ECG on me three goes because of someone with phone on in waiting room.

Real big signs saying turn phones off too. So many people don't realise about polling and think if they are not talking on it then it's OK. Some will even turn themselves back on. Mine did that in hospital I had set alarm so I would not miss appointment then went in early and at alarm time the phone turned itself back on.

To a lesser extent blue tooth and WiFi also cause problems my PC was set to wake up on lan and when my son came with his PDA it would auto start my PC.

My mother with a pace maker is not suppose to use a mobile but in public places how does she avoid them especially in a wheel chair so her hart is at pocket height? Putting on notice on her wheel chair please turn of mobiles is not really an option.

 

[ban-all-sheds]

Go here: http://www.csl.sri.com/users/risko/risksinfo.html

Subscribe.

Sooner or later the subject will crop up - it'd probably be worth searching the archives too.

 

[ban-all-sheds]

I,m also concerned at the amount of RF energy around us, there are already concerns with mobile phones, and we now have many high power transmitters churning out multiplex digital signals which themselves are at radio frequency.