Somewhat funny stuff

["ABLE1" <royboynospam@xxxxxxxxxxxxx>]

Found this discussion over at alt.electronics.  Those Brits are all the rage
some times.
Kinda enjoyed the read and thought I would share.



We have a wireless network at work which appears to have gone downhill since
the workmen installed PIRs for the burglar alarm.  One of them in particular
appears to cause dropped packets the closer a laptop is to it.  Is this
possible??  It's not a wireless PIR as far as I know, as I can see some
leftover cable he was using which is a multicore (about 10 cores) type
similar to phone systems, so I assume this is for the signal aswell as
power.  The person in that office swears blind that there were absolutely no
problems until the PIR was installed above her desk, and now when I check,
about 60% of the packets are being dropped.  Moving her laptop to the
opposite side of the room it drops only 5% of packets.  PIRs used to just
pick up infrared of your bodyheat, but I think now they are also motion
sensors?  Perhaps this means they are sending out a signal and bouncing it
off you?  Perhaps this could interfere with wireless networking?

--
> You can now get ones that use microwave detection as well as PIR, they
> are called "Dual PIR" sensors:

> 10.5GHz for the microwave
>
> A normal PIR sensor would not cause any issues like this as they are
> passive.
>
> You can simply swap a Dual PIR for a normal PIR no probems.

Good point, I'll just tell them to put in a passive in any rooms with
problems if I can prove it's that.

We've always had detectors though and never had problems, so maybe it's
faulty?  Or the new ones are on a different band.  If it's using 2.4GHz, in
my opinion it's wrong.  Using the same band as wireless networks in an
office is just plain stupid.

> Sensors only need a 4 conductor cable, two for power (12V), two for the
> contact.

Odd that they left a bit of approx 10 core cable then (and that was the only
thing they were fitting at the time).  Unless it uses a different core for
each type of detection?

A normal PIR sensor would not cause any issues like this as they are
passive.

You can simply swap a Dual PIR for a normal PIR no probems. Sensors
only need a 4 conductor cable, two for power (12V), two for the
contact.

> ---
> If its PIR it shouln't.
>
> PIR is Passive Infra Red, and it's body heat which triggers the sensor,
> not anthing the device transmits.
>

I'm not sure if it's PIR or not.  Aren't a lot of them nowadays
multifunction?

> Maybe the wiring is affecting the strength of the RF field areound where
> she sits.

The wiring?  It shouldn't have that strong a field from its wiring surely?

The effect is as such: within about 2-3 metres the network is unusable.  The
next 2-3 metres it works most of the time.  After that it's almost perfect.