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So, you're interested in the idea of using your computer to control your CB, huh?

Well, you've come to the right place. I have developed a simple and easy-to-use system that will allow you to interface almost any 40-channel CB to your Windows 95-compatible computer (must have Centronics-style parallel printer port; tested with Windows OS's up to XP 32-bit, NOT tested with any 64-bit system, and not tested with USB-parallel port adapters). Any CB that has PLL expansion capabilities can be taken advantage of with this system.

Click to purchase a complete parts kit and software for the discrete transistor version of this system. $19.99 shipped. Includes all elecronic components needed. You supply enclosure and connecting supplies. Note, this price is for domestic orders only! Orders outside of the US are welcome, but additional shipping charges apply.

Here is the original project write-up: (this project was originally conceived prior to 1998 as a DOS-based computer interface, but not documented online. The following constitutes the first on-line documentation for this project.)

Here are the basic ideas behind the system. The average 40-channel CB (and many export models) uses a fairly simple Phase-Locked-Loop (PLL) system to tune in the various channels. The PLL chip iteself uses a set of digital programming lines to determine which frequency the system is to generate. These lines are normally controlled by the channel selector and/or band switch. They could just as easily be controlled by a set of toggle switches, or a set of digital output lines from a device such as a computer. Thats where the fun can begin. By using the simple interface I have designed, you can use the printer port of any IBM-compatible computer (running Windows 95 or higher) to control the programming lines of the PLL chip. This allows any radio with an expandable PLL (such as a Cobra 148 gtl, or a Uniden Grant) to be taken advantage of. The interface can control up to 8 programming lines, or 255 seperate frequencies. With the additon of a monitoring line using the input lines of the printer port, we can monitor the transmit pin of the CB mic jack, and have the computer change to a different channel when the radio is keyed. This gives the CB split-frequency operation. Those of you familiar with the RCI 2950/70 radios know what a nice thing that can be from time to time. By using this system, ANY compatible CB radio can have that ability!

As of January 2003, I am once again working on this project. The old file system has been changed to include the radio name, and the old DOS software has been discarded in favor of Windows-95 compatible software, currently under development. The features are a basic 40-channel controller with split-transmit ability, and an expanded-frequency controller with split-transmit ability. I will post the demos on this page as I complete them. I will post screen shots from time to time, as well.

June 21, 2004: Due to requests to purchase the schematics/software, I am posting the schematic, and making the software available for $20.00. Once the software is purchased, you will have unlimited access to any data files that are written. The purchased package will come with data files for MB8719 PLL circuits (Cobra 148 GTL, etc), am-only PLL02A (older Midland/GE radios among others) circuits, and basic TC9102 PLL (Uniden PC66, Cobra 25LTD, etc) circuits. The data files can be writtin by hand with any common text editor (I use Notepad in Windows), as long as the data structure is understood, and the data order is followed. I plan on developing a datafile utility when time permits.

February 24, 2006: Finally got around to rewriting the software to get rid of some major bugs, and simplify the interface. So far, its working very nicely. The data file utility is a long ways off, though. I also worked out a couple more data files, but need to work on others.

Here is a screen-shot of the latest version of the software:

April 24, 2006: All bugs seem to be gone, all help files are written, and the PLL data file utility is done. I've completed an installation CD, which includes the application files, along with schematics for both versions of the electronics for the interface. From time o time, I will be listing the system CD (with all of its included diagrams and utility programs), on Ebay. Listings will come and go, so if you do NOT see a listing for this software from us, just email for details on how to obtain your copy directly. We DO accept Paypal.

Here is what the CD will look like:

July 21, 2008: I was just made aware of some bootleg copies of this software being sold on Ebay by someone out of the UK. Be aware that these are NOT legitimate copies, and will NOT be supported in any way! I have not entered into any agreement with any entity for distribution of this copywrited software.

Purchasing bootleg copies (of any copywrited material) violates both US and international copywrite laws, can result in very stiff fines as well as jail time. Civil suits for compensation may also be filed by the owners of copywrited material.

I have personally used this system with a Uniden PC 66, Uniden PC68, Cobra 148GTL, GE 5813B, Uniden Grant XL, Cobra 21XLR, and a Galaxy DX959. It can be adapted to many, many more radios, as well!

Here are a couple images of the prototype interface. The newer designs are simpler, and use fewer parts.

Inside view of the prototype interface unit.

Another inside view showing more detail

Rear view showing connectors. Uses standard DB-25 and D-sub 15 connectors

Additional wiring info for Ebay version of the system:

Schematic note: Some resistor values may not be shown. Assume all non-labeled resistor values to be 2.2k ohms.

Basic connection of the interface to the CB is fairly simple. Isolate the CB's PLL chip data pins from the rest of the circuit board and connect them to the interface as shown on the schematic, making sure to observe the location of the least significant and most significant data pins (data bits). A max of 8 data pins may be used. If more than 8 pins are used on your chip, you will be limited to the least significant 8 data pins. If you do have more than 8, make sure that the rest are isolated from the circuit board and tied to logic low. If your PLL chip uses less than 8, simply leave the unused interface data lines disconnected

The transmit control output on the interface hardware is simply connected to the transmit pin of the mic jack on the radio. For radios that need to have the mic present on receive, you may need to wire a relay between the interface and the radio, using the interface TX output to engage the relay coil in TX mode. The relay contacts would then be wired so that in RX mode, the RX pin of the mic is grounded, and in TX mode, the TX pin is grounded. The relay coil would have one end tied to 13 volts, and the other end tied to the TX output of the interface.

Here is a rough diagram of the relay wiring:


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