[RFI] RFI & Alarm Systems?

Roger (K8RI) k8ri at rogerhalstead.com
Fri Aug 3 23:52:18 PDT 2012

On 8/3/2012 10:06 AM, qrv at kd4e.com wrote:
> You could try a big 440 amp in your mobile and see how good their
> incoming filters are ... the problem may resolve itself when they
> protect it against incoming overloading they will also stop their
> unintentional illegal jamming 'broadcasts'.
>> : There is one I drive by nearly every day that wipes out a portion of the
>> : 440 band.

That was me.

It's a motion detecting alarm system. I haven't used the 440 band in the 
car for some time except for cross band repeat, but back when I was 
operating 440 mobile I'd hear it over quite a bit of the band.  "I 
think" it was a high frequency sweep across a portion of the band. 
Whether it was centered on ISM in the 440 band or not I don't remember. 
  There are a lot of link frequencies just below the 435 spot and I use 
a link frequency for a cross band input.

>> What exactly are you hearing from it?  Intentional RF or incidental?

It would have been intentional as it is checking for movement.
Call it a poor mans RADAR.<:-))

>> is an ISM band (Part 15) from 433.05 to 434.79.  I usually monitor 433.925,
>> 434.000 and 434.500, but I have equipment operating throughout that range.

Repeater links are some where around 431 something, IIRC.


Roger (K8RI)

>> Almost forgot 418 MHz, lots of stuff there.  Alarms operate throughout the
>> spectrum.  I have a transmitter next to me that operates from 150 - 276 KHz.
>> Then there was some stuff around the AMBC band, article surveillance systems
>> throughout HF, MILLIONS of devices covering six decades around 27 MHz, then
>> 49 MHz, also some stuff around 33, 40, 72 and 76 MHz, 150 MHz, 210-215 MHz
>> or so,
>> 250, 275, 290, 303 and 308 are quite common, as are 315 and 318 MHz, then
>> there was the stuff in the 80's that didn't change codes, but frequencies,
>> 290-410 or so if I recall correctly, 434 is common, commercial stuff around
>> 450-470 MHz, the entire analog cellular band, but 868 MHz is the most common
>> now, throughout 902-928 with stuff centered on 915 MHz being the most common
>> and now 2.4 GHz where the garbage out there exceeded all other bands
>> combined long ago!
>> If you want to know what frequency your equipment operates on, check the FCC
>> ID database:
>> http://transition.fcc.gov/oet/ea/fccid/
>> Kurt

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