Re: 4 . Wireless alarm systems INTERFERING sources>

["Dr. Phred" <fred.spearey@xxxxxxxxxxxxx>]

I'm new here but I'd like a chance to voice an opinion. RFI is
everywhere on this planet and is ceated by just about everything on and
surrounding this planet. It is true, RFI is real, but if it was really
all that much of a problem almost anything electronic wouldn't work. RFI
is transmitted thought the air (radiated) and though wires (conducted).
This is simple elementary knowledge. Anything electrical can generate
it, have you ever tried to listen to a radio when the wife vacuums?, or
tried to use a CB when sun spot activity is high. It can cause concerns.
But it is in no way as bad as I have some people talk about in this
group. If a product was so suseptible to RF that it wouldn't work, the
UL or FCC wouldn't give it their approval. I can hardly believe that a
grown man would spend hundreds of hours campaining about the pitfalls of
wireless alarm simply because he probably had an install go bad in the
past that he couldn't resolve. There are literally millions of wireless
alarm system in the world and if they were so unreliable as to fail
every time someone shaved next door, I'm sure the manufactures would
have been driven out of business years ago. I have only discovered a few
wireless problems that have become a mystery to resolve. I have found as
many strange quirks with wired systems, some resulting from RFI( yes,
they can suffer from that too). All I can say is, I'm not a fan of air
cooled engines, but I didn't spend my life trying to run Volkswagon out
of business. I hope that these people realize that as they waste their
lives whining about the BIG RFI problem, they're only creating more with
each key stroke...

-pull@shoot wrote:
> What type of signals are able to produce RFI (Radio Frequency
> Interference) on Wireless Alarm Systems and will jeopardize they're
> operation?
>
> 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
>