Electronics > RF, Microwave, Ham Radio

Detecting very low power motion sensors

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LaserSteve:
That picture has a plastic cased SA point blank into  an unmatched waveguide.  A bare  1n914 diode would detect a signal  at that point.  In that picture the SAs front end is massively overdriven, so it sees the harmonics in the mixer. .  The SA would not see the far weaker signal of a tiny transmitter which would  be close to or below its noise floor.

Sorry, You need a better instrument or a professional.


Steve

ejeffrey:

--- Quote from:  glradio on April 22, 2024, 02:23:10 am ---
TinySA Ultra can detect motion sensor frequencies around 10 GHz, in these examples

--- End quote ---

I thought it only went  to 6 but I now see there is a higher frequency version. My understanding is that it has much worse sensitivity above 6 GHz so I would count on it working.


--- Quote ---Could ultrasonic sensors work reliably through a wall ?

Is it possible to somehow detect the emissions of ultrasonic sensors placed behind a wall ?

--- End quote ---

Depends on the wall and the sensor.  Going from wall to air, reflecting, back to the wall and to the sensor is probably a tall order?  It's also possible to hide things by e.g. drilling a hole in the wall, mounting sensors in the hole, skim coating it and painting over.

A microphone with an audio signal analyzer would work as long as the microphone works up to the frequency in use.  I think the things used in parking sensors are like 40 kHz?

glradio:

--- Quote from: LaserSteve on April 24, 2024, 05:46:30 pm ---... The SA would not see the far weaker signal of a tiny transmitter which would  be close to or below its noise floor ...
--- End quote ---

That's what I think too: the power of these sensors is so low that the TinySA Ultra does not have the necessary sensitivity to see the emitted signal ...

I was wondering whether an antenna made from a short "stub" of wire (like the one shown below) of the appropriate length to receive the emission frequencies of motion sensors, would change things appreciably or whether it would be better to try a higher-end device ...

Teledog:
Perhaps they're RCWL-0516 microwave motion sensors. Low power & can pass through drywall, etc.
They run @ ~3.181-3.2 GHz.
G'luck! :-+

glradio:

--- Quote from: Teledog on May 02, 2024, 04:07:44 am ---Perhaps they're RCWL-0516 microwave motion sensors. Low power & can pass through drywall, etc.
They run @ ~3.181-3.2 GHz.
--- End quote ---

I have that sensor and have done some bench tests.

The TinySA Ultra has no problem detecting it even when placed behind a wall about 30 cm wide.

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