Alarm problems.

Notice:
Poor design or fitting of alarms can cause false alarms or failure to be triggered when they should. The type and positioning of sensors is important, so should be chosen by proper alarm installers.
Due to the problems of noise, laws have been put in place regarding alarms. Anyone making, modifying or fitting alarms should be fully aware of the law and technical issues regarding alarms. As well as specific alarm laws, it should be noted that having constant false alarms may be considered to be "anti-social behavior".
The author does not encourage dabbling in circuits that you do not understand or the fitting of alarms by people unaware of correct fitting methods.

What is the problem?
Burglar alarms triggering for no apparent reason are a known problem. On some estates, where alarms are on almost every house, alarms can be heard often going for no reason. The most common problem associated with this is that alarms may be ignored. In fact, police may refuse to attend most cases of alarms being triggered. If an alarm is often falsely triggered, it may lead to people making complaints about the noise.

What can suffer from this?
Any burglar alarms, although wireless systems can be more prone to problems.

Who's fault is it?
This depends upon the type of alarm and the cause.
Clearly, a wired system which does not use RF should not pick up any signals. In such cases, picking up any external signals suggests poor alarm design. However, if you use excessive power then you should not be surprised if your signal causes problems.
Although wireless systems do use RF, as the frequency is much higher than CB, a legal CB radio should not interfere with any burglar alarm. In cases of shared band interference, I would blame the problem on the government department who allocated the frequencies.

What causes it?
This depends upon the type of alarm and the situation. Possible causes include:
  Poor alarm fitting
  Faulty alarm sensor
  Poor alarm design
  Sharing of band
  Smart burglar using tactics
  Excessive power from CB
  Problems with CB

What should I do about it?
In any case, but particularly with car alarms, check for:
Poor alarm fitting:
Check the positions of sensors. Check whether pets in the house could be setting the alarm off. PIR detectors may be triggered by sudden temperature changes, objects blowing in the wind, etc. Direct bright sunlight may also cause problems with sensors.
The smart burglar using tactics.
Burglars have been known to purposely trigger alarms, then run and hide. If the owner hears the alarm, they will reset it. So, once again, the burglar sets off the alarm and hides.
He will play these games until you decide that the alarm is faulty and switch it off or stop using it... jackpot.
Always be aware of this trick and keep your eyes open.

Children playing games.
If there are sensors that may be triggered from outside, then it is possible that children may trigger the alarm with a ball. Maybe innocently, but maybe they like to see you running around looking for the problem. Children will play.

If the problem is uncertain and the alarm is wireless, check for:
Identical alarms:
Does a neighbor have a wireless alarm? Although each alarm has a code, cheap alarms can have as few as 1024 different codes. This may seem plenty, but not on an estate where alarms are all over and close together.
Shared use:
A good indication could be whether other alarms are being affected. If other alarms are affected, you may be able to find the source - where is the interference centered? The real problem is that there are now so many wireless products used in homes, so pinning down a particular item may be difficult. Even if you do, will the person stop using it when your alarm is on?

If you are absolutely certain that your CB equipment is causing it, then check:
Antenna position:
Wherever possible, your antenna should be mounted as high as possible and as far as possible from any equipment that may be affected.
Coax.
The use of old or cheap coax may cause more signal to be radiated by the coax, rather than the antenna.
Antenna tuning:
Poor tuning of the antenna can cause the coax to radiate signal, which will be lower to the ground and closer to other equipment. It is in your interest to make sure that as much of your signal as possible is sent out at the antenna.
Do not leave your SWR meter in line:
As the SWR meter can cause losses and produce harmonics, it should only be connected while testing the antenna.
Modifications:
If your radio has been modified, particularly for extra channels, have it checked out to see if it is the problem. An unmodified, legal UK CB radio should not give out harmonics at a high enough level to cause problems.

If all else fails:
Consider changing the alarm.
Wireless alarms could be real problems, especially on crowded estates or in blocks of flats. They should not be fitted without considering whether you really need a wireless system and just how likely there is to be interference at some point in time. Even if they work fine when fitted, you cannot be sure what equipment you or a neighbor may use in the future and it may interfere.

As a last resort.
Warning:
This really is a last resort. Do not do this unless all other possibilities have been tried including, if possible, replacing the alarm - as it opens up your alarm to attack using a jammer. This means that a smart burglar can disable your alarm with small transmitter set to your alarm frequency. Also, if the problem is caused by a local signal, that equipment may act as a jammer, making your alarm useless whenever that equipment is switched on.

Anti-jamming circuit
Wireless alarms should have something called "anti-jamming" built in. This is designed to detect if someone tries to disable your alarm using a jammer.
Unfortunately, with the amount of wireless products in home use now, this more often gets set off by some innocent wireless product transmitting on the shared wireless band used by the alarm.
It is often possible to disable this circuit, and the alarm instruction manual may tell you how. If in doubt, consult the alarm fitter - please do not mess with what you do not understand. Please remember the above warnings.