Show HN: RF Hunter – Find hidden cameras and other devices

Fun fact, you can actually detect semiconductor devices even if they are powered off and hence emit no radiation unless the design took specific precautions. This works by illuminating a region with high frequency electromagnetic radiation and then listening for the effects that PN junctions have on the reflected radiation due to their nonlinearity. [1]<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nonlinear_junction_detector" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Nonlinear_junction_detector</a>

2018, <i>&quot;Low budget consumer hardware espionage implant&quot;</i>, 220 comments, <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=40363704">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=40363704</a> &amp; <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20190251">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20190251</a> &amp; <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=15676737">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=15676737</a><p>2019, <i>&quot;Airbnb Has a Hidden-Camera Problem&quot;</i>, 50 comments, <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24324300">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24324300</a><p>2019, <i>&quot;How to find hidden cameras in your AirBnB&quot;</i>, 300 comments, <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20457419">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20457419</a><p>2023 repro of &quot;Great Seal Bug&quot; (1952): mechanical microphone, no power source, data exfiltrated via external directed microwave beam, <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NLDpWrwijE8" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NLDpWrwijE8</a><p>Try measuring the RF emissions of:<p><pre><code> USB hubs AC power strips SSD enclosures monitors</code></pre>

Thanks for making this public. What&#x27;s the ballpark BOM cost?<p>Could a directional antenna help with locating RF sources? There&#x27;s some older work (&quot;WokFi&quot;) on parabolic antennas for WiFi, <a href="https:&#x2F;&#x2F;web.archive.org&#x2F;web&#x2F;20140802123553&#x2F;http:&#x2F;&#x2F;www.usbwifi.orconhosting.net.nz&#x2F;" rel="nofollow">https:&#x2F;&#x2F;web.archive.org&#x2F;web&#x2F;20140802123553&#x2F;http:&#x2F;&#x2F;www.usbwif...</a><p>Here&#x27;s another circuit design for AD8317, <a href="https:&#x2F;&#x2F;g8rwg.uk&#x2F;articles&#x2F;noise-meter-ad8317&#x2F;" rel="nofollow">https:&#x2F;&#x2F;g8rwg.uk&#x2F;articles&#x2F;noise-meter-ad8317&#x2F;</a><p><i>&gt; The AD8317 module I’m using has the logarithmic slope set to 22mV&#x2F;dB. I used the output of a Viavi JD785 at different frequencies to check the slope and dynamic range of the device. Linearity and dynamic range at 1GHz and 3.5GHz is good and as expected drops off at 144MHz and 6GHz.</i>

The most effective way would be use a Thermal Camera, because a normal &quot;hidden camera&quot; you get from eBay will consume around 5 Watts - a significant heat dissipation.<p>For others, probably just get an off the shelf TinySA?

This is cool. Is is all point-to-point wired inside? I can&#x27;t imagine a PCB design would be too difficult if all the RF stuff is handled by the IC.

What I really want is something that detects any EMF above 60Hz.<p>When I was a kid I used to hook a coil of wire and a diode to a piezo earphone. I then listened to the emissions of various devices in my house. My Amiga 500 was particularly interesting.<p>I ran across a few projects that do the same thing but add an opamp and recording so you can generate sounds for electronic music.

A way easier solution to this is to turn off all of the lights and look around with your phone camera.<p>The phone camera will pick up the bright IR lights that hidden cameras use to illuminate the room-- wireless or not.<p>Obviously this only works if the camera uses IR lights, but pretty much all of the sneaky ones do.

Title is misleading. It only detects RF. A hidden camera could record to storage for later upload in which case wouldn’t be transmitting continuously.

I have long dreamt about building a portable phased array for this purpose, but additionally using the phase difference between receivers to visualize where the transmission source is.<p>In effect a camera into the RF world!

Does anyone have a personal experience with finding a hidden camera in an AirBnB?

What is the sensitivity&#x2F;range? I&#x27;ve always wanted something like this to carry in the woods to detect game&#x2F;trail cameras. Not for any nefarious purpose, but to get an idea of how surveilled the woods are.

This doesn&#x27;t do anything useful. To detect RF transmissions you need to sweep a range of frequencies stopping at each frequency for a period of time for the Rx amp to sample. The AnalogDevices detector that is uses needs to be programmed, and the arduino code doesn&#x27;t do that. It doesn&#x27;t have the bandwidth or performance to do any real scanning. There&#x27;s a reason why spectrum analyzers cost thousands (or tens of thousands) of dollars.<p>Its funny watch Arduino (ease) programmers try to figure out RF (very hard).

In Japan there was a requirement to make a noise when taking a picture on a phone. I&#x27;m not a huge fan of that since there are a lot of reasonable reasons to not want noise, but I would be a fan if any capture device was require to advertise its presence wirelessly to make it easy for any smart device to notice an active recording device nearby. That wouldn&#x27;t stop sophisticated surveillance but it would act like a cheap lock and stop a lot of the abusive stuff, or at least let people more quickly notice it.

OP, cool project. I have questions though:<p>How does the device detect very short bursts? After looking up the data sheet of the RF detector I believe you would need additional circuitry to not risk that very short bursts slip through the sampling of the ESP A&#x2F;D input.<p>Second, the supply voltage of the detector seems to be 3.0 V to 5.5 V, <a href="https:&#x2F;&#x2F;www.analog.com&#x2F;en&#x2F;products&#x2F;ad8317.html" rel="nofollow">https:&#x2F;&#x2F;www.analog.com&#x2F;en&#x2F;products&#x2F;ad8317.html</a>

&gt;&gt; It&#x27;s useful to find hidden cameras, wiretapping devices, and other RF-enabled devices.<p>Nope. It is used to find RF-<i>emitting</i> devices, the sort of low-sophistication stuff you can buy online for real-time continuing surveillance. For many decades, the real spy stuff has operated in burst mode: collecting data quietly and only transmitting it at an agreed time or in response to an external signal. To detect them you need to be monitoring 24&#x2F;7 with a rig capable of triangulating signals that might only last a second or two.

Following the amazon links in the cpp brought me to this: <a href="https:&#x2F;&#x2F;www.amazon.com&#x2F;gp&#x2F;product&#x2F;B07FHZXTCZ" rel="nofollow">https:&#x2F;&#x2F;www.amazon.com&#x2F;gp&#x2F;product&#x2F;B07FHZXTCZ</a><p>Holy fsck, the build quality must be shitty if even the amazon photo looks horrible (just look at the area around the voltage regulator)

Thanks for this useful project. Can I trouble you to add a circuit diagram of the latest rev? So much easier than reading text.

Interesting, thank you for sharing!<p>Maybe somebody knows: Is there something similar for the Flipper Zero?

Is the ESP32 mainly to drive the LCD display and provide a numeric readout, or is it also needed to control the sensor-side so that it cycles through different settings and frequencies?

Cool project! I&#x27;d buy one of these if they were pre-assembled.

Might also be useful for initial EMC compliance testing, maybe.

Those 128x64 displays are easy to use, but frustratingly variable. They have differing start up sequences which using the wrong one leaves a blank screen.

This is really cool! Have you considered using a Software Defined Radio or would that not improve capabilities enough to be worth the hassle?

A thing for talking to rfids might do this. Some phones have an rfid thing. If it could sweep a frequency range.

Really interesting.<p>Could you please make a video showing well it works for different sources?

I lost a keyfob a long while ago. I wonder if this could help me find it?

I&#x27;m confused, what RF does a camera typically emit, and why?

That&#x27;s fascinating! Did you check the accuracy?

Very cool! Could this work for detecting nearby drones?

This is ineffective against most recording devices.

Does it get confused by nearby WiFi transmitters?

<i>&quot;If you don&#x27;t have a 9V battery, you can use a 9V battery.&quot;</i>

it seems multiple ESP32s would fit into this giant case.

looks good, now I just need a version of the same software that runs on my phone so I don&#x27;t need to buy all these materials and slap them together