🚀 go-pugleaf

toujours le m�me Belge qui est m�content de son alarme par radio
et qui parle USA maintenant
quel pollueur !


<p?aul@aol.com> a �crit dans le message de news:
td2u50l7d3044sl8pjtrrckate6bjlf82s@4ax.com...
> On Mon, 22 Mar 2004 16:43:32 +0100, Paul   i don' t read
> <mail@aol.com> wrote:
>
> >What type of signals are able to produce RFI (Radio Frequency
> >Interference) on Wireless Alarm Systems and will jeopardize they're
> >operation?
> >RF Transmitters operating:
> >- ON the wireless frequency
> >- Saturating the receiver
> >- Intermodulation
> >- Harmonics
> >- Falling in the receiver bandpass
> >- On the IF frequency
> >- 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.
> >
> >Not all Radio Frequency (RF) transmitters are able to generate RFI,
> >they have to be in accordance to certain rules described hereafter.
> > Find here with more detail the list of Radio Frequency (RF)
> >transmitter sources generating RFI mentioned here above:
> >
> >1. RF transmitters operating "ON" the Wireless Alarm Systems
> >   frequency.
> >   This is the most annoying RFI, it require only a very low power to
> >   do so (in my REAL case, 1 milliWatt was enough);
> >
> >2. RF transmitters "SATURATING" the input stage of the Wireless Alarm
> >   Systems RF receiver
> >   A transmitter "close" to the operating frequency may have enough
> >   power to saturate the RF receiver input stage.
> >   This signal overrides the normal incoming RF sensor signals.
> >   This can happen with permanent installed RF transmitter stations or
> >   temporary operated (CB, Radio Ham, ++) mobile or fix.
> >
> >3. RF transmitters causing "INTERMODULATION"
> >   "In gross" its the mix of two signals that result in an on
> >   the frequency signal of the Wireless Alarm Systems due to the
> >   non-linearity of wireless RF receiver input stage.
> >   It can be defined as a beat tone generated by two signals where
> >   the mixed beat part is on the Wireless Alarm operating frequency.
> >   Realize that quite a fair amount of combinations may produce
> >   that sort of RF signal.
> >
> >4. "HARMONICS" of a RF transmitters falling in the Wireless receiver
> >   frequency bandwidth.
> >   All transmitters generate harmonics, those harmonics have to
> >   be suppressed (EMC requirement) to a certain degree,
> >   nevertheless there are still attenuated harmonics and when you
> >   have to deal with a powerful RF transmitter they may still be
> >   sufficient to "muzzle" the RF receiver sensor inputs of the
> >   Wireless Alarm Systems.
> >
> >5. a RF transmitter signal not directly on the frequency who is "NOT
> >   ATTENUATED" enough by the RF "receiver bandpass filters".
> >   The RF receiver's use already since approx. 20 years SAW filters.
> >   Those filters attenuate the beside the frequency incoming signals,
> >   however those signals are still coming true in an attenuated manner
> >   but they may be of a sufficient amplitude to "interfere" the RF
> >   receiver sensor inputs.
> >
> >6. RF transmitters on the IF (intermediate frequency)
> >   Modern wireless receivers use frequency conversion techniques
> >   who uses and IF stage to narrow the bandwidth (easier on lower
> >   frequencies).
> >   One drawback with them, if the IF frequency is not attenuated
> >   enough by the input stage, a RF transmission on that frequency will
> >   pass and generate RFI.
> >
> >As you see there is a quite some impressive number possible of RF
> >transmitter sources that may generate RFI on Wireless Alarm System
> >receivers.
> > The major problem being that specific RFI avoidance techniques, used
> >in military and by similar instances, are not affordable for wireless
> >alarm systems even if the FCC (or like instances) would allow this
> >type of avoidance techniques in wireless alarm systems.
> >
> > RFI is expectedly most of the time (and lucky enough) of the
> >involuntary nature and not persistent but in the meanwhile the system
> >is deaf and when it comes to security realize how easy it is to have a
> >Wireless Alarm Systems disturbed... dead.
> > Silent key, NO ALARM, NO DETECTION.
> >
> >Paul
>