Saturday, March 26, 2016

Listening to local 700 MHz Simulcast public safety

This post is somewhat geographically specific.  For those seeking information on a police scanner for Green Bay/ Brown County. But I figured it was time to share as folks in other areas are still having issues monitoring simulcast systems.
Shortly after the new Brown County Radio System was put in place in 2013, I discovered all the scanners on the market at the time could not deal with simulcast as the county transmits from 8 towers at the same time.  

Since that time scanners with APCO 25 Phase 2 support have started to appear.  One would suspect a totally different receiver design for TDMA/Phase 2.  I have heard reports that the Uniden BCD436 does handle simulcast pretty well. (Yet the BCD996P2 does not)

Linear Simulcast Modulation (LSM) is a trademarked term for a form of CQPSK that provides a way for receivers to properly handle multiple identical transmissions. It's just different enough that the regular C4FM processing doesn't work correctly.

A friend of mine has been able to successful listen using a Pro-106 using an attenuator/ yagi combo. He lives in close proximity to one of the towers with a line of site view.  He effectively can listen to just one tower with this approach.  I was not successful with this method as I am more centrally located and probably more importantly is that I do not have a line-of-site path to any one site.   So I have multipath compounding the simulcast problem which is all too much for a C4FM receiver design to handle.

Another possibility that I only briefly explored in early 2015 was trying to listen using a RTL SDR:

I ran into many headaches and never got it working correctly so I gave up.  But I encourage others to give it a try.  As time goes on, I am sure the software will be more refined and easier to get going.  It would sure be the cheapest way to listen; a RTL dongle coupled with a Raspberry Pi micro computer would be ideal.

In late 2015 I learned that local two-way dealer is selling XTS5000 radios programmed as scanner for $900.  He also can sell transmitting radios to authorized users.  Out of my price range but at least it's an option.


So at the time (2013) the answer seemed to be to look into using a commercial radio as a scanner.  I choose the XTS-2500 as my radio based on price and availability.  Other capable radios include the XTS1500 and XTS5000.  From what I have seen the XTS1500 is usually comparable in price to the XTS2500.  However the chances of finding a used XTS1500 with the desired/required feature set is less common.  Whereas the XTS5000 is more common than both, but is typically more expensive.

I totally lucked out and bought a refurbed demo radio from a Hong Kong ebay seller that had little feedback for $250.  Others have picked up XTS2500’s for around $300.

There are a few different hardware models of the XTS2500.
Model 1: Basic, with no display

Model 15: Large bitmap display  (a display is needed if you want to see what talk group it has stopped on)

Model 2: Large bitmap display and navigation buttons (the navigation buttons are nice if you want to manipulate the scan list on the fly)

Model 3: Large bitmap display and full keypad  (the full keypad has no advantage as a scanner)

There are two main features required for the XTS2500 to work on the Brown County System.

1.) First is has to be 700 MHz capable.

Rebanding support in the Astro25 platform was introduced in Host R07. - 1/3/06

The model number theoretically dictates if the radio is rebanded of not. If the model number ends in a "2BN" in the codeplug the radio will not do 700 nor will it be able to do any digital features!

If the radio was flashed up to a "7BN" then it will be a standard xts2500 that will allow for 700 and all of the available flashcodes for that particular model line.

However, going by the model number on label as the radio, doesn’t necessarily mean it’s not capable.  If someone later updated the firmware/flashkey to Host 07 or above, it will work

2.) Second is must support a 9600 baud.  If it supports this is will obviously support digital, and the type needed for Brown County’s system

To determine this, as well as other features you need to look up the radio's flashcode"