QuadRF can spot drones and see WiFi through my wall • Hacker News Board

Re: QuadRF can spot drones and see WiFi through my wall

#141

Post by cluckindan » Fri, Jul 10, 2026, 9:23 PM UTC

iamniels wrote: post #97

its_down_again wrote: post #88

Earlier quoted context omitted.

Has anyone tried acoustic imaging for water leaks inside walls? I live in a multi-floor 1900s Victorian. A leak can affect several units, and tracing the source can mean opening walls or floors in multiple places, and coordinating access has been getting harder with less WFH. Could one of these tools help map water pipe routes and trace a leak, or are they only going to be useful for air and gas leaks?

For a water leak a sound imaging device is not going to help you. You should definitely try a thermal camera. Any moisture will create small temperature differences which are easily picked up by a thermal camera.

Moisture camera. Now there is an idea.

Re: QuadRF can spot drones and see WiFi through my wall

#142

Post by varjag » Fri, Jul 10, 2026, 9:26 PM UTC

lazide wrote: post #139

varjag wrote: post #128

Earlier quoted context omitted.

FPV drones in the Russian war are generally pretty dumb devices, there's usually no frequency hopping involved to begin with. They have a lot more in common with baby monitors than with modern military comms.

Lol, even baseline DJI drone chipsets from a decade ago do frequency hopping. Many baby monitors probably do too.

You can literally see the analog video links in countless thousands of published recordings. Nobody really does the hopping with analog video.

Re: QuadRF can spot drones and see WiFi through my wall

#143

Post by semi-extrinsic » Fri, Jul 10, 2026, 9:33 PM UTC

tredre3 wrote: post #100

FuriouslyAdrift wrote: post #81

Earlier quoted context omitted.

I have $100 devices in industrial devices that have them. In bulk, they cost next to nothing (not quite as cheap as RFID but getting there).

But in your scenario they are an integral and necessary part of the device, so it's costed in. In a television it's an added cost and it's unclear if serving ads really can offset that extra $25-100 of hardware (and included data) you ship on a $200-1000 television. It's also unclear to me if the low data packages they come with would be enough to serve meaningful ads to begin with. Those devices usually come with a…

> In a television it's an added cost and it's unclear if serving ads really can offset that extra $25-100 of hardware (and included data) you ship on a $200-1000 television.

Amazon seems to have done the math and found that it makes sense to give a $20 discount on a $180 device if it lets them display very unobtrusive ads on the lockscreen. So I don't think you are correct.

Re: QuadRF can spot drones and see WiFi through my wall

#144

Post by mallets » Fri, Jul 10, 2026, 9:37 PM UTC

mrtnmcc wrote: post #136

mallets wrote: post #130

Earlier quoted context omitted.

The really intriguing part is the "Custom ADC" here, seems like some kind of 1-bit ΣΔ oversampling ADC (704 MSPS?). Single differential transistor, and captured by FPGAs LVDS RX. Neat way to reduce cost and pin-count? But I think the typical FPGA clock tree has poor jitter performance. Not using the internal PLL(s) might help with spurs but the clock buffers are unavoidable. The documentation mentions it's likely fur…

We've got the switching noise nailed down. Fortunately the LVDS jitter doesn't affect the sigma delta too badly because that impacts proportional to baseband frequency which is largely filtered out by the decimation filters beyond 40 MHz.. With a total of eight ADCs per QuadRF, you can see we are getting huge savings by being custom! While the per-ADC ENOB is 7-8 bits, another nice thing about phased arrays is that t…

Yeah, jitter doesn't matter too much at low frequency IF. I/Q calibration is more likely to be the bottleneck. That and close-in spurs from the fractional PLLs.

I have very little experience with MIMO / phased-arrays, this application likely doesn't need ultra high SFDR.

Re: QuadRF can spot drones and see WiFi through my wall

#145

Post by mrtnmcc » Fri, Jul 10, 2026, 9:40 PM UTC

mallets wrote: post #144

mrtnmcc wrote: post #136

Earlier quoted context omitted.

We've got the switching noise nailed down. Fortunately the LVDS jitter doesn't affect the sigma delta too badly because that impacts proportional to baseband frequency which is largely filtered out by the decimation filters beyond 40 MHz.. With a total of eight ADCs per QuadRF, you can see we are getting huge savings by being custom! While the per-ADC ENOB is 7-8 bits, another nice thing about phased arrays is that t…

Yeah, jitter doesn't matter too much at low frequency IF. I/Q calibration is more likely to be the bottleneck. That and close-in spurs from the fractional PLLs. I have very little experience with MIMO / phased-arrays, this application likely doesn't need ultra high SFDR.

Yes, I actually designed the I/Q calibration for many of Analog Device's transceivers (AD93x), and indeed it is a fun problem. If you're interested in what was done for QuadRF, you can read: https://QuadRF.com/cals/txqec.html (Warning: Math!)

Re: QuadRF can spot drones and see WiFi through my wall

#146

Post by andrewstuart2 » Fri, Jul 10, 2026, 9:43 PM UTC

mrtnmcc wrote: post #136

mallets wrote: post #130

Earlier quoted context omitted.

The really intriguing part is the "Custom ADC" here, seems like some kind of 1-bit ΣΔ oversampling ADC (704 MSPS?). Single differential transistor, and captured by FPGAs LVDS RX. Neat way to reduce cost and pin-count? But I think the typical FPGA clock tree has poor jitter performance. Not using the internal PLL(s) might help with spurs but the clock buffers are unavoidable. The documentation mentions it's likely fur…

We've got the switching noise nailed down. Fortunately the LVDS jitter doesn't affect the sigma delta too badly because that impacts proportional to baseband frequency which is largely filtered out by the decimation filters beyond 40 MHz.. With a total of eight ADCs per QuadRF, you can see we are getting huge savings by being custom! While the per-ADC ENOB is 7-8 bits, another nice thing about phased arrays is that t…

I like to think of myself as pretty well-versed when it comes to hardware and software and even some RF. But this conversation has me hitting search a lot, lol. It's fascinating reading experts talk about a domain I have less experience in.

Re: QuadRF can spot drones and see WiFi through my wall

#147

Post by mrtnmcc » Fri, Jul 10, 2026, 9:45 PM UTC

mschuster91 wrote: post #109

mrtnmcc wrote: post #101

Earlier quoted context omitted.

check out https://QuadRF.com/docs/

So, essentially, the secret sauce is tracing a known calibration source's movement to compensate for different cable lengths or weird physical tile arrangements? Neat!

Yes-- but it's open sauce!

Re: QuadRF can spot drones and see WiFi through my wall

#148

Post by developer5502 » Fri, Jul 10, 2026, 9:54 PM UTC

mrtnmcc wrote: post #95

QuadRF creator here. Happy to answer questions! We have a quick demo video as well: https://m.youtube.com/watch?v=QvniJk3uNyA Along with a deeper dive video: https://m.youtube.com/watch?v=zdJ9Tbm8ALg We didn't give Jeff great direction on camera alignment calibration or setting the radio gain but he seemed to mostly figure it out. We're improving the UI based on his suggestions (it's open source so you can customize…

Super cool project I've been following for a while. Are you pivoting away from Earth-Moon-Earth radio astronomy? I first bookmarked this project when your site was hosted at https://open.space

Re: QuadRF can spot drones and see WiFi through my wall

#149

Post by NopIdoN » Fri, Jul 10, 2026, 9:59 PM UTC

lowbloodsugar wrote: post #140

piinbinary wrote: post #48

One day I want to build something like this, except for sound. It would be great to get a heading and distance for where a sound is coming from. This could be both for small scale things (e.g. which part of this is squeaking?) or large scale (e.g. is that booming noise coming from the construction a few blocks away?)

I want that but for smell.

You could try training wasps.

Re: QuadRF can spot drones and see WiFi through my wall

#150

Post by mallets » Fri, Jul 10, 2026, 10:08 PM UTC

mrtnmcc wrote: post #145

mallets wrote: post #144

Earlier quoted context omitted.

Yeah, jitter doesn't matter too much at low frequency IF. I/Q calibration is more likely to be the bottleneck. That and close-in spurs from the fractional PLLs. I have very little experience with MIMO / phased-arrays, this application likely doesn't need ultra high SFDR.

Yes, I actually designed the I/Q calibration for many of Analog Device's transceivers (AD93x), and indeed it is a fun problem. If you're interested in what was done for QuadRF, you can read: https://QuadRF.com/cals/txqec.html (Warning: Math!)

Oh wow, the AD936x series was impressive for its I/Q calibration. Still is I guess, because there's been no compelling alternative even a decade later.

As I mostly deal with single channel applications, I get to use double superhet and avoid runtime calibration. Not an option here, Zero-IF has too much in the Pros column for multichannel.