Re: 4 . Wireless alarm systems INTERFERING sources>

[-pull@shoot]

On Wed, 04 May 2005 21:54:57 -0600, "Dr. Phred"
<fred.spearey@xxxxxxxxxxxxx> wrote:

>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.

True, wireless is useable when power and receiver quality is
implemented.
 The power of Wireless Alarm Systems is LOW (<10MilliWatt)? receivers
are basic/elementary.

>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 come back on that extend of certification in an other post.

> 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.

Its resolved, replaced with a WIRED ALARM SYSTEM.

> 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,

Not all equipment cause RFI. Read what is said.

> 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.

? Manufacturers should be driven out of business, that simple.

> I have found as
>many strange quirks with wired systems, some resulting from RFI( yes,
>they can suffer from that too).

Ill come back on that one too.

>-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
>>