Picture of How to Make a $19 Police Radio Scanner
In this guide I will explain how to build an inexpensive SDR (software defined radio) that can be used to receive police, fire, taxi, and other digital radio transmissions. I will do my best to explain the steps in detail, and provide further resources to help along the way.

For the radio enthusiasts, this setup is capable of following trunked, digital voice radio transmissions with a single receiver.

Read the full howto here:

Video of completed setup:

I have to give a lot of credit to the creator of the following guide: This how to is based largely from that, and other sites listed in the Resources section.

Please use the information in this guide responsibly.
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Step 1: Hardware Requirements

Picture of Hardware Requirements
The only hardware required besides a computer is going to be a SDR receiver. The bulk of these radios are just USB TV tuners, rebranded and sold as SDR receivers. Many are available on Amazon and eBay. A quick google search should turn up some more as well. I recommend purchasing from somebody who knows about SDR, a popular dealer is (NooElec also has stores on eBay and Amazon)

In this guide I will be using a Newsky TV28T v2 with a RTL2832U & R820T tuner.
MichaelD142 months ago

I seem to have gotten SDR to work but the voice reception is choppy. Does anyone have a solution to improve this?

is2dsky5 months ago

Nice write-up.. Up to the point of configuring UniTracker Control. Under model there is no debug option. Suggetions? Thanks..

I'm using UniTrunker version and the initial creation screen includes a button for Debug. Once created, I left the type as debug also and it seems to work okay.

what kind of antenna would you suggest for someone to make this work optimally?

I followed the instructions but am only getting extremely intermittent transmissions on the control frequency for my county public service trunk control. I've tried the alternates no difference with those as opposed to the primary control frequency. I'm only using the antenna that came with my usb software radio so I figure that this is woefully inadequate.

I'm having the same issues.Got everything working but many conversations are choppy. One thing that helped my reception was to put the antenna on a metal surface. I used an old cookie sheet and it seems to help considerably. I have a friend who is Ham Op and will ask about antenna choices. Something small that I can keep in the house rather than mounting on the roof.

Cmdr_Jim1 year ago

I have a 2 dongle setup and all appears to be working fine except I have no sound what so ever. Am I missing something everything is configured as to the article, in sound properties record is set to line 1 vac and in playback it is set to speakers.


My local police/fire does not use trunking, What steps can I elimate just to receive digital non-encrypted traffic?/


MajorHavoc1 year ago
Need help please! In step 17, I can tune to a few different good control signals. However, I am not getting any new windows to pop up! Ideas? Thank you!
pichulo1 year ago
Need help. Got stuck on step 17(sptep SDRSharp trunk radio guide). Unitrunker does not display the "site" window as described int the step. I have followed both guides to the letter, but no luck.
Yes, it controls. But jumps very fast between voice chanels, so I hear nothing. How to tune it to one ID or group?
tryed, still no control from UniTrunker (
lyletanner1 year ago
I prefer the VB-Audio Virtual Cable instead. Very simple and it's donationware:
harrysand (author)  lyletanner1 year ago
I will have to check that out! I searched high and low for a free alternative to VAC and came up empty handed...
Hi, Harrison! I have one dongle and set it all as described in your article (single tuner configuration). But all that SDRSharp listens just control channel, and doesn't jump to the voice frequencies, in spite of the UniTrunker lists all of the target ID's in this time (look at the screen). I'm novice in this, what do I wrong?
harrysand (author)  romandocent1 year ago
You seem to be really close to getting everything to work!

I would first suggest setting the filter bandwidth to 12500. And also taking a look again at the section that talks about calibrating the tuner, you can see the red line in your screenshot is a bit to the left of the signal. If you take care of those issues the signal quality in UniTrunker should improve.

Also, the Minimum Signal Level (in the screenshot you sent me) should be set to something around -30 or -35. The goal is to set the number to a level above the noise floor but not too high so that it will ignore a signal. My guess is that this is what’s keeping SDR# from changing the frequency… Keep in mind if you adjust your gain settings this value will need to be changed again.
jimmyaggie1 year ago
This is what I have so far. The first picture is the SDR program along with the DSD and Unitrunker. The second picture is the Unitrunker Installation directory. I can't seem to get Unitrunker to control SDR so I was wondering if I did anything wrong.
New Bitmap Image.bmpNew Bitmap Image.bmpNew Bitmap Image.bmpNew Bitmap Image.bmp
the same problem (
GeekSkunk1 year ago
Thanks for pulling this together, very helpful. Quick question - With 1 RTL-SDR should I expect to actually hear anything, or just see it decode with DSD? Seems everything revolves around the VAC. Audio output of SDR# needs to be the VAC, U-Trunker uses that as the input (so does DSD I think).What gets the decoded sound out of the computer speakers? Hoping its just a setup issue I have.
harrysand (author)  GeekSkunk1 year ago
You are correct, UniTrunker and DSD will use the same input that comes from SDRSharp. You direct the sound out of SDRSharp into the line 1 device, and set up DSD and UniTrunker to listen to line 1. When tuned to the control channel Unitrunker will decode tuning information, and when tuned to a voice stream, DSD will decode the voice information. You should absolutely be able to hear sound out of DSD. Double check and make sure that Line1 is set as the "Default Recording Device" in windows sound properties and that Unitrunker is set to listen to Line1. Go back over the final steps in the guide and make sure you didn't miss anything. Hope this helps!
rj443191 year ago
I don't see the Trunking tab in SDR#?
knack1 year ago
Small calculator icon?

I found mpt1327, i see the call, joins but frecuency its 0.0000. any ideas?
perhaps its encrypter? how i known if its encrypt?
znorris1 year ago
Great article. You re-kindled my interest in SDR. I bought a couple during the craze and never really did much more than listen to the radio. This has been a fun re-awakening. I am having troubles finding the correct frequency. I've tried looking up the Illinois State Police trunk on but can't seem to get anything out of it. Maybe a new antenna? Thanks again for this!
harrysand (author)  znorris1 year ago
Thanks! I just used the antenna my receiver came with, pictured above. On the system in my example there were a bunch of control channels but I could only actually receive one or two. I think they are only a few miles away. Upgrading the antenna might be an option to look into. But before you spend money, see if your county has a trunked system, you probably have better chances at being close to one of those. Also do you see consistent streams in SDRSharp, but just have no luck getting UniTrunker to pick it up? That could point to a configuration issue.
I was able to tune into a local trunk and UniTrunker was able to see it. So that's good. I've attached a picture of it so you can see what I'm getting.

How did you pick the frequency for the police trunk? I guess I'm not entirely sure I'm tuning to the correct freq.
harrysand (author)  znorris1 year ago
You're actually closer to getting it working than you think! The green bars in the top left of the UniTrunker window means that you are successfully connected to the control channel and your antenna should be okay! By looking at the 8D01 in the UniTrunker window I can see you're tuned to this system here:

I dont think that is a police system. For Illinois I would try looking here and finding the control channels listed in your county or nearby counties:

Also, you are using a newer version of SDRSharp that doesn't (yet) have a compatible trunking plugin. I have a download link under the Software section to the version you need. Then take a look at the end of the tutorial that shows how to configure the plugin.

Hope this helps!
harrysand (author)  Kiteman1 year ago
(removed by author or community request)