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Notes on the Uniden MR8100 Scanning Receiver By Mike Morris WA6ILQ

Photo by Jason Bishop W4IRQ

Depending on who you talk to this unit was designed for either the California Highway Patrol, the Los Angeles Police Department, or the Feds. No matter who gets the credit, it was introduced in 1989 with an advertised frequency range of 29-54, 118-174, 406-512, 806-956 MHz in AM and FM. This is a well-built and laid out scanner. The enclosure is made with cast aluminum and there are numerous internal shields to isolate the various sections of the receiver. One of the really different points was that it was a "vertical" design, backlit, and was intended primarily for mobile use. As far as I know, it was the first scanner that had a serial port and matching computer software that could load the preprogrammed channels, in this case 10 banks of 10 channels. It does not have an internal speaker, and uses a 4 ohm or 8 ohm external. Like any device, it has it's flaws, and one is that while the display indicates frequency out to four decimal places, the firmware only accepts three decimal places for PLL programming. Thus while you -think- the radio is tuned correctly to one of the "splinter" channels, it's not. Another is that there is no search and store capability. The unit ran on standard 12 volt vehicle power, and drew less than 800 mA. The antenna fitting is a regular BNC female. In 1990 it was listed at US$499.95, by 1992 the price had dropped to around $270. The programming cable is a "straight-through" 9-pin to 9-pin cable.

The advertised range was not the "full" range (29-956 continuous), and the full range could be unlocked if you knew the secret key... it's in one of the files below.

Some of the attachments:

• Owner's Manual   The original factory owner's manual, scanned. If anyone has a better scan, please send it in.
• Uniden supplied software documentation
  Includes a link to download the factory software. Note that it is DOS based software and must be run from DOS, not in a DOS window.
• Block Diagram  664 KB PDF
• Technical Specifications
• A breakdown of the serial data protocol   Author Unknown
  With this anyone could write a new upload/download program.
• Technical Observations on the MR8100 Frmware and Programming Software   Author Unknown
• A list of common birdies   18 KB PDF
  Early computer controlled synthesized scanners had a problem with the digital microprocessor logic creating signals that the receiver section would hear. These are called "birdies".
• SK Consultants Interface Software Instructions 26 KB RTF file.
  This software is aftermarket software that is much better than Uniden's. It is DOS-based software and must be run from DOS, not in a DOS window. The software (34kB ZIP file) can be downloaded here.
• Windows based MR8100 software.   (offsite link)
  From the web site: A program to enhance PC programming of the Uniden MR-8100 (MR8100) programmable VHF/UHF scanner radio. Uses Windows interface; better than Uniden's SCAN.EXE! Lots of features, such as bank swapping, enabled cellular frequencies, Runs under Win 3.x, Win 95/98/2000, Win NT 3.x/4.x or Win XP.
  Also there's a Frequently Asked Questions page on the software (offsite link).
• This is the late Bill Cheek writeup on discriminator audio, baseband audio, and discriminator chips

Links on the web:

Search Google Groups for references to the "MR8100" OR "MR 8100" OR "MR-8100" scanner.

Artsci Publishing Inc. is a publisher oriented towards the electronics enthusiasts. They have a series of books on Scanner modifications. Look at book 10B in the in Radio/Tech Modifications series:
http://www.artscipub.com/mods/scanner.html

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This page originally posted on 03-Jan-2008

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This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.