EMC. RSGB and Intruder Alarms

EMC. RSGB and Intruder Alarms

Here is a excerpt taken from A Leaflet on the RSGB Website Entitled:

Dealing with alarm EMC problems – Advice for RSGB members (Leaflet EMC 03)

The Full Leaflet is Available on the RSGB Website

Please NOTE (READ) the Text that is underlined in red

Ham Radio and Alarm Systems

I have had years of experience dealing with Alarm Systems and here is some information

I write this article with my views to the information contained within the

RSGB

Leaflet

EMC

This Leaflet concerns Triggering of Intruder Alarms with Ham Radio transmissions.

The leaflet states that if

RF Immune Detectors are used as stated under BS4737, then Ham

radio transmissions will not trigger the Intruder alarm system.

But as I am a Electronic Security Engineer myself, and having spent many years with large

national Intruder Alarm companies , I find the information not quite correct.

Yes it does help to have RF Immune Detectors fitted, but even so I have proven over the

years that alarms can be triggered by RF, (An acquaintance of mine use to boast that he

parked his car outside a factory to Deliberately set the alarm system off), this triggering can

be caused by other errors in the installation that were un wittingly done when the system was

installed.

For example, I have found in numerous cases that re-running a wire from say the control

panel to the detector

in question can cure the problem, this could be caused because that

particular cable run was at the correct length for the particular band of transmission causing

the activation to act a bit like an antenna and pick up the transmitted signal and cause the

problem, thus re-running the cable in a different and say longer or shorter run would cure it.

It would of course be a good idea to use screened cable too, but most systems are not

installed with screened cable due to its increased cost.

Quite a lot of the more modern up to date control panels have to use screened cable so this

does not come in to play.

I have had a Fire station triggering the alarm system on a indoor shooting club, this clearly

was a concern to the police, again, re-running the cables and even fitting suppression

capacitors and RF chokes to the DC output at the control panel and even the detectors can

cure the problem, as it did in this case (Over 20 False activation from this club inside a 2

week period before I was called to have a look, as most alarm service engineers have no

knowledge of RF at all).

Of course it goes without saying that a well designed and installed intruder alarm system,

using the best quality materials and care in the placement of the system parts would be the

best approach from the onset and hopefully will give years of false alarm free use to the

customer.