Types of Scanners

Steve,

Hopefully I've provided enough information below that you can use this for forwarding to others. I own Uniden brand scanners with the exception of one older Radio Shack scanner that was made by Uniden. While I do not think poorly of the Radio Shack models, I have found that the Uniden equivalents usually have features that I desire. I have tried to keep any bias out of the write-up below and have just put down the basics.

1) Types of scanners

There are basically two types of scanners.

1. Plain frequency scanners simply monitor frequencies within their given frequency ranges (more on that below). They usually scan either a frequency range or memory locations that have stored frequencies. These scanners are great for non-trunked systems, airport, rail and business monitoring.

2. Trunk tracking scanners differ from plain frequency scanners in that they can track "trunked" radio systems. Trunked radio systems are used primarily in metropolitan areas by everyone from police/fire/EMS to utility companies with fleet vehicles. Trunked radio systems are used because a large number of users (radios) need to be packed into a limited number of frequencies. The frequencies assigned to the system are shared by a number of logical channel ID's that rotate through the frequencies. Individual user radios are set to a given channel ID. The central radio system transmits a data signal over a data frequency (that may or may not change over time) that tells all radios the current frequency for all channel ID's. The individual radios monitor the data signal and change frequency for their channel ID according to the central system data. Trunk tracking scanners monitor the data signal and follow the channel ID's across the frequencies. A person trying to listen to a trunked radio system with a plain scanner would be able to hear the transmissions on the frequencies, but because the channel ID's move across frequencies, following a conversation (say the north side police dispatcher) would be difficult at best. They also would not be able to limit the channel ID's that are heard, for example the trash truck crew. Trunk tracking radios monitor only the channel ID's that are programmed into their ID scan lists. They can also be used as a plain frequency scanner.

2) Trunk radio systems

There are a number of different trunked radio system manufacturers. The primary types used by police/fire/EMS are Motorola (Type I, Type II, Hybrid, SMARTNET and PrivacyPlus sub-types), GE/Ericsson EDACS, or E.F. Johnson LTR. The most prevelant type seems to be Motorola Type II. Each type uses a different trunking/data scheme. Most trunk tracking radios will cover most of these types. There are other types of trunking systems, but they do not seem to be widely used. There are also two types of trunking within these trunk types, analog and digitally encoded (APCO-25). Traditional scanning is analog, like your FM radio. You tune to the frequency and listen to the transmission. APCO-25 systems use digital encoding in the transmission. If a person were to try to listen to a digital transmission wtih an analog scanner, all they would hear is a data stream, similar to what a person hears when they use a dial-up modem or fax machine. Since 9/11, there has been a concerted move for agencies to go to APCO-25 digital radio systems. At this time, not all major metro areas have gone digital. The best thing to do is check http://www.radioreference.com to see if your local system is digital. If it is, you will probably have to purchase a digital trunk tracking scanner to listen in. Also, ask around local electronics stores and see what they recommend. A Google search for trunk radio and APCO-25 will bring up a great deal of information.

3) Some things to look for in a scanner

Frequency coverage - Not all scanners cover the same frequency ranges. Make sure the scanner you are looking at covers the frequencies you need.
Sensitivity vs. selectivity - These refer to the scanners ability to pull in weak signals and to separate signals. For the average person in a metro area sensitivity is not a concern. Selectivity becomes the issue because the FCC is splitting the frequency spectrum into smaller segments, i.e., cramming more usable frequencies into a given frequency range. In scanning this is referred to as step size, i.e., the number of kilohertz between selectable frequencies. Scanners with lower selectivity have a larger step size and will pick up transmissions over a broader range, possibly resulting in transmission interference if two transmissions fall within the scanner's step size. Programmable selectivity is usually available in the newer scanners.
Scan rate - This is the number of memory locations and/or frequencies that are scanned per second. Slow units will do only 20 memory locations
Number of memory locations - Older scanners may only have 100 memory locations. Newer scanners will have 1000 to 5500. The newest scanners simply have a memory pool that stores all items, similar to a PC.
Frequency search/auto store - Automatically storing frequencies is real handy when you are in a strange area and do not have the frequency list.
Desktop vs. handheld - Obviously a handheld will be much more usable while on the move regardless of the mode of transportation.
Antenna connection type - Traditionally BNC-type connectors are used. Recently Uniden used an SMA-type connector for their new scanner. This is important if you need to build a cable to connect to an external antenna.
Power consumption/battery type - Watch for what type of batteries the scanner uses. Uniden used to use battery packs that cost about $50 to replace. Their newest scanner uses AA's. Radio Shack scanners most often use AA's.
Terrain and foliage of the area - If you are planning on sheltering in place, what does your terrain and foliage look like? If you are in the mountains up in the pines, you probably won't need a trunk tracking scanner. The radio systems used in metro areas need line-of-site and mountains get in their way. Also, the frequency the trunked systems use is usually sucked up by pine needles that act as little antennas and take the radio frequency (RF) energy and put it right into the ground making it go absolutely nowhere (Funny Story - When Michigan deployed their state-wide APCO-25 digital trunked system, they found them virtually unusable in the Upper Peninsula where pine trees are dominant. They had to go back to non-trunked lower frequencies that were not affected).

4) Manufacturers/Approximate prices (no guarantee on the price here - just an idea of the price you may pay)

Radio Shack:
Plan scanners range in price from $99 to $150.
Non-Digital Trunk Tracking scanners range in price from $150 to $230
Digital Trunk Tracking scanners are $500.

Uniden:
Plain scanners will cost anywhere from $100 to $200 range.
Non-Digital Trunk Tracking scanners range in price from $180 to $300 range.
Digital Trunk Tracking scanners consistently run from $475 to $550. The prices have not dropped over the years they have been available. STAY AWAY FROM THE DISCONTINUED BC250 MODEL!! It only tracks an earlier version of APCO-25 that is not widely used. Stick with the BC296 or the new BC 396 or their tabletop equivalents.

5) Sources for scanners

Uniden scanners are available from a number of different retailers. Prices can vary, so check for the best deals. This list contains the dealers I've used most often. Radio Shack scanners can only be purchased from Radio Shack. http://www.usascan.com - Usually the lowest prices for Uniden scanners. http://www.aesham.com - A ham radio dealer that also sells Uniden scanners. Also sells Unisolar flexible solar panels.
http://www.hamradio.com - Another ham radio dealer with Uniden scanners http://www.radioshack.com - For Radio Shack scanners
http://www.grove-ent.com - High prices on the scanner but has some good scanner antennas
http://www.uniden.com - Lists all of their scanner models and has downloadable owners manuals so a person can review the manual before buying. http://www.ebay.com - Yes, there are good deals out there. You just have to look for them.

6) Sources for police, utility and other frequencies

http://www.radioreference.com - This is the first stop I make when wanting to look things up. They not only have a great frequency database but they have discussion forums based around manufacturer, trunking, specific topics (rail, air, etc) and each state specifically. Look here for information on your area before buying a scanner for the first time. http://www.trunktracker.com - This site is geared around Uniden scanners but has a bunch of good info.

I hope this wasn't too overwhelming, but I wanted to provide everyone with a starting place.

Paul Olson
Tulsa, OK

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