12 Meter Modification

The CHIPSWITCH   IC is programmed to allow for a base frequency coverage of 24.800 to 29.999 MHz, 12 through 10 meters. However, because of limitations in the original UNIDEN designed Phase Locked Loop (PLL) circuitry, most radios will also require optional 12 METER MODIFICATIONS to actually transmit and receive at 12 Meters. Just the installation of the CHIPSWITCH chip will allow you to 'dial in' frequencies down to 24.8 MHz, but most radios' PLL circuits will lose 'lock' below about 25.5 MHz, thus rendering transmit and receive inoperative at these lower frequencies. The optional 12 METER MODIFICATION provides transmit and receive operation over the full 24.8 to 29.9 MHz range of the CHIPSWITCH microcomputer chip. The 12 METER MODIFICATION consists of installing a number of small components that are soldered onto the backside of the PLL / MICROCOMPUTER circuit board, the same board that the CHIPSWITCH chip is installed on. Expensive electronic equipment might then be needed to adjust various circuits. Installation and final adjustment require about 3 hours.

AVAILABILITY / SOURCE

Please note that 12 METER MODIFICATION is only available through a few sites at this time. Modifications do not need to be done at the same time as the CHIPSWITCH chip is installed.  CHIPSWITCH does not have a kit available. Derrell Adams and others have developed a list of modifications, which they install to the PLL PCB.  Please call these people before you ship your radio and make payment arrangements.  If you have yet to buy the Chipswitch IC, please buy all desired items from their company. Rogerbird's Modification Web Page describes his version of the 12 Meter modification procedure.