Where 1990 scanning is exactly the same in 2016 – RF Scanning 101

Because “Where 1990 scanning is exactly the same in 2016 – AND – where it’s completely different” was too long of a title.

I’ll start building off my previous post.  As a reminder, in 1990, your programmed RF Radio scanner looked like this:

Channel 1 – 460.025
Channel 2 – 460.050
Channel 3 – 460.075
Channel 4 – 460.100

Modern day radio towers are lower to the ground than 1990 radio towers.
Modern day radio towers are lower to the ground than 1990 radio towers.  There are also more of them.  1 radio tower in 1990 is usually split into 2 or 3 regional towers in modern day systems since the tx/rx of higher frequency radio waves require it.

Fast forward to 2016 where your receiving scanner (trunked under the hood) looks like this:

Frequency 1 – 460.025 (control channel; aka computer)
Frequency 2 – 460.050
Frequency 3 – 460.075
Frequency 4 – 460.100

Notice the addition of the computer, or control channel, in 2016.  Modern repeaters, known as digital infrastructure radio systems, are computer software driven.  To simplify the functionality, the computer (freq 1) is constantly listening to all computer programmed frequencies to see if someone wants to talk.  The computer knows who wants to talk by the pressing of the push-to-talk (PTT) button on the radio.

To better understand how the radio system functions, I’ll play out the following case scenario:

Freq 1:
Reminder, the computer is constantly waiting for someone to talk then temporarily assign them to one of the available freqs.  Freq 1 is listening on this system and is using freqs 2, 3, and 4 as available freqs.

Freq 2:
When Mayberry police officer 1 presses the talk button on her two-way radio, the control channel tells her portable radio to use the selected frequency (we’ll say freq 2 since nobody is using it).

Freq 3:
At the same moment freq 2 is assigned by the computer, Mayberry fireman 1 starts using his truck radio to call the dispatcher.  The computer searches then tells the fireman’s truck radio to use freq 3.

Freq 4:
Assume the officer on freq 2 is still talking but her partner is on a foot chase and presses a mayday emergency button on his portable radio.  The mayday signal (a HELP alert) is sent to the computer.  The computer is smart enough to override the police officer on freq 2 and tell the dispatcher that he (the officer now assigned to freq 4) needs help.  The computer is programmed to know the mayday call is a higher priority than regular communication so the dispatcher is now in direct communication with Mayberry officer 2 even though officer 1 was originally talking.

So this scenario is as follows before freq 4 in use:

pic credit: policemag.com
pic credit: policemag.com

Frequency 1 – 460.025 (control channel; aka computer)
Frequency 2 – 460.050 (Mayberry police officer 1)
Frequency 3 – 460.075 (Mayberry fireman 1)
Frequency 4 – 460.100 (available for use)

THEN, after Mayberry police offer 2 pushes the HELP emergency button:

Frequency 1 – 460.025 (control channel; aka computer)
Frequency 2 – 460.050 (Mayberry police officer 1)
Frequency 3 – 460.075 (Mayberry fireman 1)
Frequency 4 – 460.100 (Mayberry police officer 2 – HELP)

Isn’t this stuff great!

So we have learned that your scanner in 2016 can scan the exact same freqs as in 1990, but the modern scanner has morphed in functionality and is basically a mini-computer programmed through software to understand it should constantly listen to the radio tower computer (control channel).  The control channel computer does exactly what software programmers have told it to do, and your scanner is constantly listening to the control channel for the same reason – so the scanner will know what freq to choose and listen to at any moment.

Because this is all software driven, any changes to the system software may require you, the listener, to modify your scanner settings to match the system software.  You may also notice a delay in how fast your trunked scanner receives audio from the tower making it sound as if you joined the middle of a conversation.  That’s partly because scanners are searching wide ranges of freqs – they’re not tuned exactly to your local tower.  You can finely tune the programming of your local system since pre-programmed frequencies usually scan a full range (A – Z) rather than specific freqs (just G instead of A – Z).  But that’s getting a little too complex for this post since a site like RadioReference.com usually updates their frequencies by the time the listener realizes there is a problem.

Next RF Scanning 101 post > The control channel plays air traffic controller.

Scanning in 1990 – RF Scanner 101

Scanning in 1990 was so simple it involved 3 steps:

  1. Set scanner to manual
  2. Input desired frequency on the numeric keypad (such as 460.025)
  3.  Press the enter button to save the change
Old school Uniden BearCat 175XL
Old school Uniden BearCat 175XL

It really was that simple

… and still is that simple –  at least the fundamentals are that simple in 2016.

Every modern radio system is made up of frequencies and they’re just like the ones from 1990.  Notice the 460.025 frequency (aka: freq) in the adjacent image.  Assuming you’re located in a densely populated area, you could input that same freq in your scanner today and hear someone or something making noise because the same old freqs are still in use.  It was common in 1990 for 1 “agency” (think police precinct) to be assigned to 1 freq.  So here is what your scanning list looked like in 1990:

Channel 1 – 460.025
Channel 2 – 460.050
Channel 3 – 460.075
Channel 4 – 460.100

Most old school scanner functionality stopped here and left the translation up to you.  So you, the listener, had to know that Channel 1 was “Town Police Department”, Channel 2 was “Town Fire Department”, Channel 3 “Sheriff’s Department”, and on, and on.  This is where the simplicity of 2016 radio scanning changes.

Simple?  Then why is it so complicated to program modern scanners?

To de-complicate today’s scanning, I’ll build on the 3 simple steps from 1990 (presented above).  To make things more efficient, today’s radio systems (the term used for modern repeaters) share freqs with multiple agencies. So 1 freq (such as 460.025 MHz) may be used by 10 to 15 different agencies.  But these agencies don’t just share the 1 frequency – they share anywhere from 10 to 15 different frequencies.

Police Call 1990 (Old School) Edition. Police Call Radio Guide was the pre-internet RadioReference.com commonly sold at Radio Shack stores.

It’s time to stop talking and start playing so get that shiny new scanner out.  Use the RadioReference.com database to find your local police department freqs.  Just click here, choose your state from the map, then narrow down to your local county and city.  This will give you the freqs needed for your locale.

Next, use your scanner vendor website (such as Uniden.com) to find instructions so you can manually input 1 freq as a “conventional” type – as opposed to trunked systems.  Once entered, turn the volume up and listen for a few minutes to hear audible chatter.

That brings us up to the next RF Scanning 101 post – Where 1990 scanning is exactly the same in 2016.

Note: If you happen to hear sound similar to a machine gun while listening in conventional mode, that means you found the control channel.  The control channel is the software running the shared freqs on the repeater, but that detail will be explained in the next post.

RF Scanner 101 for 2016 – It’s Like Yesterday – Just More Complex

Most everyone has heard of RF radio scanners but probably through different terms like police scanner, fire radio, airplane pilot monitors, and even the newer terminology like digital trunk-trackers.  Maybe you came here looking to buy a new scanner and are confused since 1990 was the last time you touched a megaHertz receiving scanner.  I’m here to de-confuse the situation with RF Scanner 101.

…the fundamentals of scanning have not changed since 1990

pic credit: ebay.com
pic credit: ebay.com

First, find comfort knowing the fundamentals of scanning have not changed since 1990.  You’ll probably think I’m crazy if you’re sitting there trying to program a modern day scanner like the Uniden BCD-996-P2.  But it’s true.  Every RF radio system broadcasting today still uses a frequency (eg: 155.700 MHz) to transmit and receive.  Where it gets more complex is the introduction of software that drives these modern day transmitters.

I’ll take the next 5 blog posts to break down each element of scanning in 2016 so we can make sense of the last few decades of changes in scanning technology.  Here is what I’ll cover:

  1. Scanning in 1990
  2. Where 1990 scanning is exactly the same in 2016
  3. The control channel plays air traffic controller
  4. Full life-cycle approach to RF radio software implementations
  5. Digital encryption stops you from having fun
  6. Bonus: Enjoy scanning today since it won’t exist in the future

I agree – number 6 is a buzz kill. But we’ll learn how to use the technology while possible.  See you in the next post.