This article first appeared in the August 2002 issue of Monitoring Times.
Over the past few months we've heard several announcements about upcoming scanners with many new capabilities and features. Most listeners enjoy the new gadgets, but is it really necessary to have the latest and greatest scanner?
Looking at a normal trunked radio system, there are three different kinds of information being sent from a repeater tower. One type is the voice traffic - the analog sound from the user who is talking. The second type of information is the sub-audible data stream that is carried along with the voice traffic, identifying the talkgroup and in some cases the user who is speaking. The third type of information is carried on the control channel (in Motorola and EDACS systems), providing talkgroup activity and overall system information.
A "regular" (conventional) scanner will receive the voice portions just fine, and as long as the system is analog you'll hear the transmissions that make up a conversation. In a pinch I've even used my venerable Bearcat BC200XLT, now more than ten years old, to monitor voice transmissions on a trunked system. That's the good news. The bad news is that you'll miss out on all the benefits of being able to make use the other two types of information.
Remember that in a trunked radio system, it's possible for many or all of the voice channels to be busy at the same time. Without any way to sort out the traffic, a conventional scanner will simply stay on a busy frequency until it goes quiet, then move on to the next busy frequency. Since in most systems there's no guarantee that an entire conversation will stay on the same frequency, you may very well end up missing more than just "bits and pieces." You'll hear part of one conversation, then jump to another part of a different conversation. I'd bet that you would become frustrated pretty quickly.
Even worse, some trunked systems, especially EDACS, have a "tail" after each transmission. Sometimes the tail is a steady tone, other times it's an irritating buzz and occasionally it's the "GE brings good things to life" theme music. No matter what it is, however, it will keep your scanner squelch open and you may miss the next part of the conversation as it takes place on a different channel. Trunk tracking scanners avoid this problem by decoding the sub-audible data sent at the end of a transmission to signal a switch to another channel.
By decoding and using the other two types of information, a trunk-tracking scanner can follow a particular conversation regardless of which channel it is on. It also allows you to ignore talkgroups that you're not interested in, which can be important if, say, two fellows in the city water department are yapping about last night's ball game at the same time the police dispatcher is coordinating a high speed car chase.
You will also miss out on seeing the actual talkgroup identifiers that a trunk tracker can provide. Figuring out the different users on a system is much more difficult if you can't reliably identify the group that each transmission belongs to.
In short, your success will depend a great deal on the activity level in the systems you're trying to monitor. For small systems that aren't very busy or large systems during the wee hours of the morning, your suggested method of monitoring might work fairly well. As long as there is only a single conversation taking place at any one time you should be able to hear each transmission and make sense of them all.
Finally, you'll quickly be reminded to do this, but remember to lock out the control channel frequency - the buzz of data is very annoying. The control channel may change from day to day, so don't be surprised if you have to lock out different frequencies on different days.
Uniden Scanner Testing
Uniden is in the process of "fine-tuning" their new digital scanners prior to releasing them. Part of this process involves checking the scanner's operation on various APCO Project 25 systems across the country.
Scott Carpenter, the Bearcat Product Manager at Uniden America Corporation, has asked for confirmed information about which APCO 25 systems are fully operational. In particular, Uniden would like to know operating frequencies in the VHF, UHF or 800 MHz bands; whether they are conventional, trunked with an analog (3600 baud) control channel or trunked with a digital (9600 baud) control channel; as well as locations that have strong coverage. If you have any solid information along these lines you can e-mail it to me or directly to Uniden at firstname.lastname@example.org.
In addition to coverage and performance problems, the trunked radio system serving the Washington, D.C., fire department was brought down for more than ten hours in June due to lightning. The $5 million digital system was installed in January of last year and operates from four towers in the District of Columbia. Lightning struck two of those towers, forcing firefighters to use cellular telephones while the radio system was down. An interesting comment came from a Fire Department spokesman who claimed the four-site system was inferior because it was actually optimized to work from 19 towers. No wonder complaints of poor coverage continue to plague the system.
BC780XLT Computer Control
In previous columns I've discussed using a computer to control the operation of trunk-tracking scanners. Depending on your radio, there may be a number of programs that make scanning easier and more enjoyable. I appreciate hearing reviews from readers about software they’ve tried, whether good, bad or a mixture of both.
This software was reviewed by John Catalano in the December 2001 issue of Monitoring Times. As a reminder, Rich Wells has a very good web page at http://www.strongsignals.net/access/content/software.html that has a good list of scanner software websites sorted by receiver type.
In March of this year the city of Canton, Ohio, contracted with Motorola for an 800 MHz trunked radio system. Two repeater sites will operate six voice channels for the city, which will also purchase 400 digital radios. The system will be "mixed mode," meaning both digital and analog radios will be supported. This allows a gradual transition to digital technology while allowing the existing investment in radios to be used.
Canton currently operates a Motorola Type I analog system on the following frequencies:
852.5375, 853.0375, 854.0375, 854.5375, 855.0375 and 860.2875 MHz. A suggested fleetmap is to use S4 for blocks 1 and 2.
Summit County, Ohio
Summit County, Ohio, and the city of Akron, Ohio, have jointly agreed to purchase an $8 million Motorola ASTRO system for public safety use that will work with the existing Akron system. This "mixed mode" system will allow the use of both analog and digital radios and is capable of being upgraded to future 700 MHz frequencies when they become available. The system will have six voice channels and operate in simulcast mode from five repeater sites. It is expected to be available in early 2003 with initial use by the county sheriff and county public works departments. County dispatch is planned to occur out of a new center located where Akron currently dispatches. Summit County is home to more than half a million residents and currently uses the frequencies 460.100, 460.1375 and 460.425 MHz for County Police.
At present the city of Akron operates a Motorola Type II (analog) system on following frequencies: 852.0875, 852.1125, 852.3875, 853.1125, 853.3625, 853.5125, 854.2625, 855.2625, 866.0375 and 866.2875 MHz. Akron Police dispatch is reported on talkgroup 2064 (hex 0810).
And yes, one of the selling points of the new system was the ability for Summit County users to interoperate with the city of Canton, which is only 20 miles south of Akron along Interstate 77.
That's all for this month. Try to stay cool in the summer heat, and check my website at www.signalharbor.com for more trunked radio information. I also welcome your e-mail to email@example.com. Until next month, happy monitoring!
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