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Guest
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 Posted:
Tue Sep 07, 2004 2:39 pm Post subject:
10/. NEWBEES, external RF transmitters disturb often Wireles |
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Don't thrust wireless alarm systems, use wired!!!
My wireless alarm system was:
- "deaf", muzzled for sensor signal reception
and
- "dead" on alarm giving
when i used a simple commercial available wireless radio headphone,
that simple ..
Its a well known radio transmission problem called "Radio Frequency
Interference" (RFI)
- present at ALL systems (old and new = external) but
- more present than normal in wireless alarm systems due to the low
power transmitters (10milliWatt) used in the sensors
AND
- the use of shared frequencies (obliged) who have disturbances and
are unprotected for RFI (see at FCC and/or other country authorities
for the world frequency band attribution scheme or www.ero.dk for
official info).
What type of signals are able to jeopardize they're operation?
External RF Transmitters operating:
- ON the wireless frequency
- Falling in the receiver band pass
- On the IF frequency (IF = Intermediate Frequency)
- Intermodulation
- Saturating the receiver front end circuit
- Harmonics
- and more...
In essence the problems caused by interference is the fact that by no
way two (or more) systems can use simultaneously the same frequency.
My wireless headphone story showed me "how simple it is" to have the
operation jeopardized completely by an external transmitter operating
on the wireless alarm frequency.
This problem is NOT REPORTED by any mean to the owner, realize what
can happen when you have a wireless FIRE detection system...
The system will no longer detect it (same for intruder alarm).
I replaced my Wireless Alarm System with a wired one; the problem is
solved for me, what about yours?
Some "extra clever pro's" say that the FCC (++) will locate and find
the disturbing signal.
1. Just realize that the local range of the disturbing signal don't
allow to locate it at distance.
2. That other legal users share the wireless alarm frequency
and that they have to find out in that bunch the one whom is
disturbing... Good luck.
Paul
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