Thousands are monitoring police scanners during the George Floyd protests • Hacker News Board

Re: Thousands are monitoring police scanners during the George Floyd protests

#191

Post by hajile » Wed, Jun 03, 2020, 2:58 PM UTC

themodelplumber wrote: post #18

catalogia wrote: post #13

Earlier quoted context omitted.

What I heard is many police departments now encrypt their radio communications, with the exception of dispatch which they keep in the clear as a concession to the media and ambulance chasers.

They also refer each other to their MDT or cell when working, which is equally effective at cutting out the public (whether intended or no). In many rural areas, analog FM voice is still in use with no encryption, which I've heard is at least sometimes due to more favorable propagation characteristics for reception at a distance.

Digital signal is clearer, but all or nothing.

I know a fire chief who told me that some stations have switched back to analog. Some firefighters allegedly went silent and their bodies were found later. I guess it's believed that they attempted to radio for help, but the "digital cliff" stopped anything at all from getting through. If they'd heard someone calling for help, they could have gone there -- even if they didn't know exactly what the issue was.

I'm sure pricing is a factor in a lot of areas. $150 will buy a decent analog radio. The same thing, but digital will cost $300-500. Cheap Chinese radios can be had for as low as $30 or so. With just 100 radios saving $200 each, you get 20k to spend on other things. That matters a lot to rural police and even more to EMS (especially volunteer groups).

Re: Thousands are monitoring police scanners during the George Floyd protests

#192

Post by Scoundreller » Wed, Jun 03, 2020, 3:01 PM UTC

vmchale wrote: post #23

Mostly listening in to news about the looters here (Chicago). Obviously I care about the protesters/rioters but they're not who I need to watch out for.

Checkout this service for Chi:

https://crimeisdown.com/audio

Re: Thousands are monitoring police scanners during the George Floyd protests

#193

Post by iNate2000 » Wed, Jun 03, 2020, 3:34 PM UTC

NovemberWhiskey wrote: post #143

ISL wrote: post #109

Earlier quoted context omitted.

It would seem reasonable to be able to FOIA the encryption keys in US locations where it is encrypted.

Even if you could, how long do you think your FOIA request would take to get processed vs. the rekeying frequency of the encryption?

key management is hard

Re: Thousands are monitoring police scanners during the George Floyd protests

#194

Post by sterwill » Wed, Jun 03, 2020, 3:49 PM UTC

sterwill wrote: post #140

voltagex_ wrote: post #117

Earlier quoted context omitted.

Will you have a chance to write up anything further about your setup?

It's just an old HP Proliant home server with a USB sound dongle, and VLC transcoding from ALSA PCM to Opus and serving HTTP. VLC does it all! My radio has a WiFi interface, but it's weird and unreliable (only supports RTSP, 401s if the requested host isn't its internal IP, crashes after 12 hours, etc). So I just use a short analog audio cable instead.

More technical details in case anyone needs to quickly pipe out some audio to the Internet:

  /usr/bin/vlc -I dummy -vv --no-alsa-stereo alsa://default:CARD=Device -L --sout-keep \
    --sout #transcode{acodec=opus,channels=1,ab=24000,afilter=equalizer}:standard{access=http,mux=ogg,dst=:9999} \
    --equalizer-2pass --equalizer-bands 0 0 0 0 0 0 -20 -20 -20 -20

--no-alsa-stereo because my input source is mono. --sout-keep probably isn't necessary now, but it was when I was streaming from the radio's crashy RTSP service.

The #transcode block sets up a simple pipeline: first transcode to Opus at the specified output bitrate (24 Kbps is plenty for recorded voice), then mux it up and serve it via HTTP. I added a low-pass filter at ~6 KHz because there's some of high frequency noise from either my radio's analog output stage or the cabling. I had to look through the VLC source code[1] to find the preset frequency bands since I couldn't find them in VLC docs.

[1] https://github.com/videolan/vlc/blob/777f36c15564b076bf13af6...

Re: Thousands are monitoring police scanners during the George Floyd protests

#195

Post by baddox » Wed, Jun 03, 2020, 4:31 PM UTC

tzs wrote: post #163

simcop2387 wrote: post #82

Earlier quoted context omitted.

This is starting to change, but it does take time since it usually requires replacing hundreds of radios at one time and a bunch of additional training on how to use the new radios properly.

Can't they run a newer encrypted system on separate channels than the older system is using, with some kind of repeater set up between the two? You'd need to upgrade at the base station upfront to have both the old and new systems, and add a repeater, but you could then take your time replacing the radios in the field instead of having to replace them all at once.

Sure, but as long as a single unencrypted bridge is running, anyone else within range of that bridge can listen, so you won’t really get significant benefits of encryption until the switchover is complete.

Re: Thousands are monitoring police scanners during the George Floyd protests

#196

Post by xxpor » Wed, Jun 03, 2020, 4:36 PM UTC

lozaning wrote: post #164

xxpor wrote: post #120

Earlier quoted context omitted.

Don't you need at least 2 to track trunked systems?

You need two rtl-sdr, but one hack-rf can grab enough of the spectrum that only one is required. One of the benefits of p25 is that it's very spectrum efficient so I get all 18 channels.

Ah the bandwidth isn't something I'd considered. That's a good point. Unfortunately for me the KCERS Seattle site's total bandwidth is about 6.5 mhz. I have a RTL-SDR and a SDRPlay but it seems like the only thing that can talk to the SDRPlay is their own software.

https://www.radioreference.com/apps/db/?sid=604

Re: Thousands are monitoring police scanners during the George Floyd protests

#197

Post by kebman » Wed, Jun 03, 2020, 4:50 PM UTC

shadowgovt wrote: post #81

kebman wrote: post #76

Earlier quoted context omitted.

Isn't police radio usually scrambled? It is where I am in Norway. It was legal to listen to it before it was scrambled though. Not sure if it's legal to de-scramble it, if it's at all possible. AFAIK you can still listen to the ambulance channel, though, but sometimes the details are ... grisly.

In the United States, no. Police, emergency, first responder radio transmissions are generally in the clear. I don't know the precise history of it, but I have always assumed it is a combination of legacy (emergency radio in the United States is very old, and predates cheap and convenient electronic encryption standards), compatibility (first responder funding and maintenance in the United States is generally a local…

Before they scrambled the police radio in Norway, they would sometimes phone in stuff to the central when they wanted to deliver personal or protected information. Sometimes they'd omit the phone-in, though, to save time.

Interestingly, tapping in on mobile phone conversations, and de-scrambling them, is legal in Norway, at least for the state. AFAIK they still don't need a court ruling to do so, like they do when they want to wiretap someone. This is because the radio waves aren't regulated the same way as wired connections in Norway. I suspect this might be similar in the rest of the EU as well (of which Norway is merely a de-facto member). It might also be something to look into if you're an American, to check whether this is also reflected in either federal or state laws.

Re: Thousands are monitoring police scanners during the George Floyd protests

#198

Post by chromatin » Wed, Jun 03, 2020, 6:18 PM UTC

RNCTX wrote: post #171

simcop2387 wrote: post #82

Earlier quoted context omitted.

This is starting to change, but it does take time since it usually requires replacing hundreds of radios at one time and a bunch of additional training on how to use the new radios properly.

A friend of mine in Little Rock connected the dots on how police were ignoring burglary reports en masse to rig the stats in favor of businesses and realtors with a vested interest in lower perception of crime than there really was. The radios were encrypted to stop him from doing so within the next calendar quarter. He was plotting dispatch calls versus FOIA reports of burglaries to find the variances. I’d expect th…

This is fascinating, and seems like the kind of thing a national-level investigative reporter would love to cover. Has it been covered anywhere or pitched to anyone?

Re: Thousands are monitoring police scanners during the George Floyd protests

#199

Post by topspin » Wed, Jun 03, 2020, 10:16 PM UTC

renewiltord wrote: post #162

topspin wrote: post #161

Earlier quoted context omitted.

It's considered unsporting and is a poaching technique. Yes, some game animals will stare into a light not understanding the threat, but the real reason spotlights are effective is eyeshine; the light reflected from the eyes of game animals makes them easy to find at night. There are many effective techniques that are not permitted when hunting game.

Oh I see. I just didn't realize that that was codified into law so that police would stop you from doing that. Would have figured it had more than just unsporting as a reason.

Here is a current publication[1] that covers the rules that apply in a typical Midwest state. Page 19 covers use of artificial lights and various exceptions. There is a great deal to know and conservation officers enforce these rules enthusiastically.

[1] https://www.michigan.gov/documents/dnr/hunting_and_trapping_...

Re: Thousands are monitoring police scanners during the George Floyd protests

#200

Post by aviditas » Thu, Jun 04, 2020, 7:17 PM UTC

blantonl wrote: post #2

Hi there! I'm the owner and operator of Broadcastify, which is the platform that powers all the apps that provide police scanners and public safety communications online. I'm an active HN reader and would be glad to answer any questions folks have. It's an interesting business to be in these days...

Have you considered putting the app on f-droid?