DSC 433 mhz Jamming Issues

[Jim Palminteri]

Is anyone having issues with RF jamming on the the DSC 433 MHz receivers? I recently discovered that thses cheap wireless door annunciators are jamming the receivers. The system then fails to pick up the devices. This caused the door signal to be missed and the door could be opened without tripping. BIG LIABILITY PROBLEM.

 

[davenn]

hi Jim

not really about what is happening....
what specifically is causing the jamming the door transmitter ?
what specifically do you mean by jamming ?
is the DSC 433 MHz receiver actually being used to receive the signal from the door transmitter?
if not what are the DSC 433 MHz receivers being used for ?

if the DSC 433 MHz receivers are being used for other projects and not related to the door system then it just shows that they are on the same freq.

433MHz is a standard LIPD freq ( LIPD = Low Intereference Potential Device) as in low intereference to other services like commercial and amateur radio services.
Unfortunately they are anuthing but low intereference, they cause horrific problems that I have to deal with every time I turn on my radio gear.

can you just explain a little clearer what is occurring, answer the above Q's and see if we can get you on the right track

Dave

 

[Jim Palminteri]

I have a standard security installation consisting of :

1. PC 5010 control panel
2 RF5132-433 receivers
1. PC5320 Multi-receiver module
1 PK5500 keypad
8 WS 4549 door sensors
5 WS 4904 motion detectors.

All the equipment is DSC.

The client had install a separate wireless door chime system on the front door alongside a WS4945 door sensor. Every time the door is opened, the receiver indicates an RF jamming condition and the system does not show the door opening. It behaves as if it were bypassed. I disconnected the chime system and the door sensor functioned normally.

 

[davenn]

ok well there isnt a lot you can do about it other than change the door chime freq
get the home owner to look for a 315 MHz system, it should be far enough away in freq to solve any intereference issues.

is the door chime at the same location as the alarm system ?
if yes then the owner may be happy to pay for the cost of the change in freq unit as these shared freq's are just that shared. There's all sorts of gear that uses them and the chances of getting intereference on 433MHz is very high.

Dave

 

[Jim Palminteri]

433 mhz jamming issue

Good idea to go to 315 MHz on the door chime. I understand from DSC that they are going to switch their modulation scheme from Direct Sequence Spread Spectrum (DS-SS) to Frequency Hopping (FH-SS). That should make the system more immune.

 

[haidao]

Good idea to go to 315 MHz on the door chime. I understand from DSC that they are going to switch their modulation scheme from Direct Sequence Spread Spectrum (DS-SS) to Frequency Hopping (FH-SS). That should make the system more immune.

It is not about the frequency issue. The 433Mhz and 315Mhz have no difference. The door application usually use the cheap RF solution, which is ASK modulation. It is easily interrupted by any tiny change of the environment. I recommend the FSK or GFSK solution if you need better performance.

 

[davenn]

It is not about the frequency issue. The 433Mhz and 315Mhz have no difference. .......

I strongly disagree.... 433MHz is full of high power transmitters in use by a large number of commercial and amateur systems that will cause all sorts of problems regardless of the modulation method of the much lower power LIPD device

Dave