In response to Bernard Green

[dpt]

Do, please tell us about your experiences of this.

I'm a fully licensed amateur radio operator I can and have built jammers and experimented with them, it's what geeks like me do.

full text was "How many occasions have you witnessed a Yale alarm, in an ordinary domestic house in an ordinary residential street, where intereference blocked the signal from a sensor?

Do, please tell us about your experiences of this."

So you have never witnessed a Yale alarm being blocked in that way, and have no experience of it.

You are making guesses about criminals who might try it.

I've done it myself. Are you suggesting it can't be done?

 

[mdf290]

You have a responsibility to use your equipment in a way not to cause inteference.

You make me laugh because now you suggest you have created a jammer that would work to jam wireless systems within a mile radius.

lol... you would like to think so. Unless you have a seperate direct power system you would simply fry your incoming mains supply with the power that would need....



Let Bernard explain the inverse square law to you and then you will be able to calculate the power you would actually need to prevent a wireless sensor signal reaching a control panel within a home.

You have got your transmitting aerial legally sighted haven't you?

 

[bernardgreen]

lol... you would like to think so. Unless you have a seperate direct power system you would simply fry your incoming mains supply with the power that would need....

That is utter rubbish and shows how ignorant you are when it comes to radio technology.

the power you would actually need to prevent a wireless sensor signal reaching a control panel within a home.

Assume the power of the sensor TX is 10milliwatts. Then assume the jammer has a 1 watt ouput. The jammer is one hundred times more pwerful than the sensor. Square root of 100 is 10 so the jammer can be 10 times further away from the receiver than the sensor is from the receiver to get equal field strength at the receiver. That will corrupt the data from the sensor if the jammer is un-modulated carrier.

Since the jammer attacking a siren can be line of sight free air from the siren and the sensor signal is having to pass through at least one wall losing some of its strength in doing so then a one watt jammer could be 50 yards from a siren and effectively block it receiving any sensor or panel signals.

One watt of ERP can be run from a battery so why are you thinking it would fry the mains.

 

[JohnD]

...So you have never witnessed a Yale alarm being blocked in that way, and have no experience of it.

You are making guesses about criminals who might try it...

...I've done it myself. Are you suggesting it can't be done..?

You mean you have blocked a Yale Alarm? That's interesting, tell us more.

 

[dpt]

You mean you have blocked a Yale Alarm?

Yes I purchased one and played around with it in my shack.

That's interesting, tell us more.

I don't think it would be appropriate to do so, needless to say motion detectors are a very weak link in the chain.

 

[dpt]

You have a responsibility to use your equipment in a way not to cause inteference.

I passed the RAE then Morse. I'm well aware of my responsibilities.

You make me laugh because now you suggest you have created a jammer that would work to jam wireless systems within a mile radius.

Yes subject to conditions, I was liberal with the mile radius depending what amplifier, antenna and the lay of the land. I could pinpoint accurately using a yagi.

I built a transmitter that is capable of "jamming/interfering" with wireless systems within it's frequency range, 433.000 range. It's a transmitter that is within my licence conditions.

lol... you would like to think so. Unless you have a seperate direct power system you would simply fry your incoming mains supply with the power that would need....



Let Bernard explain the inverse square law to you and then you will be able to calculate the power you would actually need to prevent a wireless sensor signal reaching a control panel within a home.

He did answer it

You have got your transmitting aerial legally sighted haven't you?

All my equipment is legal and above board, even my mobile set-up.

I will tell you that my friend, who lives in Gipton, had a problem with some Yale wireless alarms on his road. A complaint was made and he was visited, he explained that he had not had a complaint and was not aware of the problem, his equipment was tested and found to be clean, no spurious emissions. The complaint was rejected because the alarms were the issue.

You see just because radio equipment may be the source of interference it is often the fault of bad filtering of the equipment that has the interference. Not the fault of a clean station

 

[bernardgreen]

had a problem with some Yale wireless alarms on his road.~~~ ~~~ The complaint was rejected because the alarms were the issue.

As did a friend of mine in Waltham Abbey

it is often the fault of bad filtering of the equipment that has the interference.

Or a comms protocol that is not resilient to the interference that equipment using a licence exempt channel must be able to tolerate.

 

[mdf290]

So now we can establish that you can have your wireless system compromised if you live near a radio ham. Whose prescence would be indicated usually by a feckin great mast in their back garden.

For sure I would not recommend a wireless alarm in that scenario or next door to a taxi office.

So how many radio hams are there in action? Cant be very many as its the first I have heard of a problem.

 

[bernardgreen]

So now we can establish that you can have your wireless system compromised if you live near a radio ham.

Yes that is possible but not because of a fault of the radio amateur's equipment.

If you read it again you will see that the radio amateur's equipment was given a clean bill of health. The fault was found to be the alarm systems being unable to operate correctly in the presence of legal transmissions from a licenced transmitter.

 

[dpt]

So now we can establish that you can have your wireless system compromised if you live near a radio ham. Whose prescence would be indicated usually by a feckin great mast in their back garden.

Vast majority of amateurs don't have masts, my friend in Gipton has a 2m/70cm colinear.

For sure I would not recommend a wireless alarm in that scenario or next door to a taxi office.

This is very interesting. Why? What about all the other commercial companies, transport, doctors, security?

So how many radio hams are there in action? Cant be very many as its the first I have heard of a problem.

What you should be asking is how many devices are out there transmitting that could interfere with budget devices that are not upto the job of filtering interference. In the case of cheap wireless alarms you don't even need to be on the same frequency, front end overload, bleed over due to poor adjacent channel rejection of equipment and direct harmonics etc Just an example of the problems you can face with wireless devices.

 

[JohnD]

What you should be asking is how many alarms you you seen that have actually failed to operate when the signal was jammed at the same fraction of a second that a burglar broke in?

the rest is just speculation.

 

[bernardgreen]

another interesting question, how many alarms you you seen that have actually failed to operate when the signal was jammed at the same fraction of a second that a burglar broke in?

Not a burglar as I would be too busy calling the police to say there was a crime in progress, suspects on premises.

I have seen sensors. ( doors and PIRs ) not invoking any response at the panel during blocking of the system by transmissions from a legal and compliant common place item.

You really must learn and accept that transmissions from a single legal and compliant item can last several seconds provided they do not exceed 10% of the time ( transmitting for 10 seconds means they must then be silent for 90 seconds )

Modules in a good well designed system will not try to transmit until the radio channel is clear. They will also expect the messages they send to be acknowledged by the destination and will repeat the message if it is not acknowledged.

 

[JohnD]

what matters is not fanciful speculation about what might or might not happen.

You really must learn and accept that what matters is the actual probability that an alarm will fail to sound because interference blocks the signal at the exact fraction of a second that a burglar breaks in.

Everything else is just hot air.

 

[mdf290]

Installed 6 alarms last week and as usual part of the process of the handover is to set the alarm and imitate a burglary attempt by entering the rear of the property through a protected zone. As always the alarms activate as they have always done in this test for many years and thousands of installs. Never yet opened a patio door and found the alarm did not activate as expected.

What can I say that I have not already said about these systems and their ability to perform when used as designed???

If I kept getting egg on my face by opening doors and the alarm failing to activate then I would have to think again about their fitness for purpose.

 

[dpt]

Installed 6 alarms last week and as usual part of the process of the handover is to set the alarm and imitate a burglary attempt by entering the rear of the property through a protected zone. As always the alarms activate as they have always done in this test for many years and thousands of installs. Never yet opened a patio door and found the alarm did not activate as expected.

What can I say that I have not already said about these systems and their ability to perform when used as designed???

If I kept getting egg on my face by opening doors and the alarm failing to activate then I would have to think again about their fitness for purpose.

I find it remarkable that you are unaware of interference, professionals are so why are you not?

I wouldn't be able to sleep at night knowing I haven't done my customer a service by telling them the pit falls of these alarms.

Next time you fit one give me a call and I will show you how easy it is to jam them.