Regardless of some that try to flood the fish by mentioning unrealized performances of spread spectrum (SS) in wireless alarm systems, regardless the invalid comparisons with military equipment, everybody knows that wireless alarm systems are unreliable during Radio Frequency Interference (RFI).
WHY?
Does that Spread Spectrum (SS) do any good to interferences avoidance? Yes, of course "IF" it is applied the correct way like in military / space / ++ equipment's ($$$).
What's the correct way to implement spread spectrum?
- The hopped frequencies should be "wide spread" over different frequencies, each frequency acting likes a separate transmitter / receiver link operating on a whole different frequency.
- The receiver should be tuned to each frequency in a "synchronous" manner with the transmitter otherwise it will capture even better RFI due to hiss wide spread capture range required when the receiver is not hopped.
- The receiver should be small band and receive only the requested hopped frequency and not capture at once the whole range of spread frequencies.
First: How can the required synchronized transmission between sensor and control panel workout with "multi-sensor transmitters" operating "asynchronously" as required use in Wireless Alarm Systems? Impossible or with a high-speed multi frequency switching receiver, too expensive for the application here, to $$$.
Second: FCC (and other country authorities) regs only allow spread-spectrum use on three bands: 902-928 MHz, 2.4 GHz, and 5.8 GHz. Those bands are not available for wireless alarm systems.
3 th: Some systems implement small frequency hopping (very limited spread spectrum) feature, WHY do they let believe to sales people that there is SS in theyre system?Wireless Alarm Systems don't use the spread spectrum possibility as it should be in order to avoid interferences, they're allocated frequency spectrum is to restricted and the receiver is only tuned to the center frequency of the hopped frequencies (the large bandwidth cope with all hopped frequencies and as such is even more interference sensitive).
The design purpose of this erroneously mentioned so called SS feature is to avoid sensor location black spot problems inherent to the higher frequencies used and not to avoid RFI like some tend to let you believe.
Propagation problems and sensor location: The frequency hopping used in some wireless alarm systems is used to resolve the sensor propagation nodes problems at the receiver end when a metal objects is displaced from his initial installation setup position (car, statue, ++).
Conclusion on SS frequency hopping: Why does installer and maintenance persons think (say) that it they have better systems now? Because they have the impression that they have a more solid (better) wireless data link connection in normal operating conditions because they find it not so critical by initial sensor position setup.
That limited frequency feature, that manufacturers and sales people tend to let you believe as the latest miracle, is worse than more selective receivers designed to capturer one frequency. The wide receiver range included in so called SS systems capture all hopped frequencies simultaneously and as such open an even wider RFI susceptibility door.
Again, where are the manufacturer technical specifications about the wireless data loop involved in theyre system???? Embarrassing to show to the general public the low quality of they're equipment in that area.
Wireless alarm systems are UN RELIABLE during interference and don't warn you when they are MUZZLED.
Paul