(01-12-2016, 01:59 PM)SuperSleeper Wrote: My last foray into digital ham radio was using PSK31 with a Rigblaster unit, and that was probably in the late 1990's.
Haven't kept up with this new stuff at all, but it sound to me like you can get really cheap stuff (dongles) now that will allow you to do all sorts of stuff on the receiving end, correct?
Yes and very cheap. The dongles cost $20-$25 for the basic ones. Really don't need much more to start other than free software. It comes with a cheap, nearly-useless antenna. Though if your popo uses 800-900mhz, that little antenna will be fine.
The frequency range for the dongle is about 26mhz to 1.1ghz. If you want to tune lower you need an upconverter like Ham It Up that will convert the lower frequencies into a range that the dongle can tune.
(01-12-2016, 01:59 PM)SuperSleeper Wrote: What I would love to do is to be able to listen to city police and county sherriff frequencies here in Dixon, IL (in Lee County, IL and neighbouring Whiteside county)... I can find some frequencies, but I can't figure out if it's a trunked system or encrypted or what, exactly. Anyone know how to find out?
Best place to start looking for frequencies and systems would be http://www.radioreference.com/
Once you figure that out, if it is a trunked system, it's not encrypted, and a system that can be easily decoded, putting together an SDR solution would require either using a scanner with a discriminator tap to tune the control frequencies or two dongles. One would tune the control frequencies and the other would be tasked to tune the voice channels.
I use a program called Unitrunker to handle decoding the trunked system. Unitrunker with the two dongles is all you need to get started with trunking. Also, Unitrunker can link to RadioReference (if you have a paid subscription) and download the XML channel info for the system you want to listen to. Otherwise you will just see a bunch of numbers and group IDs.
Group ID 1022
Group ID 651
Group ID 1234
You'll eventually figure out what they are.
The XML contains the group ID and names so you'll see things like:
Group ID 1022 Animal Control
Group ID 651 County Dispatch
Group ID 1234 Fire Dispatch 1
Plus they will be color coded. Cops in blue, fire in red, animal control in green, school buses in yellow.
Oh and Unitrunker allows you to lock out certain groups. I have all the school buses locked out. Could care less about listing to those.
(01-12-2016, 01:59 PM)SuperSleeper Wrote: What would I need to purchase to get up and running with something that would allow that? Also, do you need Windows or could I run software on Linux?
I haven't got a clue as to how this stuff works - Is there a web site that introduces all this stuff to make it easier to understand? I'm probably more of an "appliance operator", for what it's worth.
is a good place to get started on info. You can buy the dongles from them or eBay/amazon. NooElec is popular but stay away from their $50+ E4000 dongles. I'm returning mine.
For Windows: SDR# (Pronounced SDR-Sharp) and HDSDR are two easy programs to get started. SDR# is updated where HDSDR is a few years old now and no plans to update it. I use HDSDR because at the time SDR# was buggy. So now I'm used to it I just load that. I've been using SDR# more though because it is updated and they have plugins where HDSDR does not.
There are linux versions of SDR software. If you are a bit of a geek GNURadio is the ticket. That requires you to 'build' the software with drag and drop components for the various software radio components. Not familiar with the linux end of it so maybe someone who is can chime in on their favs.
There are also web based servers that connect the dongle to a machine and you access it over the network with a browser.