10FM Circuits

CB conversions to 29.6MHz 



Found in the cupboard, here are some old radio circuit diagrams I've scanned for you to download. Now you can fix all those rigs you've just bought for peanuts on E*bay or off the flea market at a Radio Rally. 

 ICOM ICB-1050

 Not connected with real Icom but a 40-channel 27/81 CB with the MC145106 synthesizer that could be easily converted to 29MHz.

The original notes were taken from an article published in Short Wave Magazine by G3XSE. These allowed a quick conversion on to 29MHz by moving a few wires. I improved on these by changing the synthesizer steps from 10kHz to 5kHz and adding a +5kHz offset switch. The disadvantage of this method is that the 40 channels do not all run sequentially, you will have to figure those out for yourself! Later SWM articles by G4LBW used additional boards using 4008 cmos binary adders to give a repeater offset and correct the display.

Improved Version

This was a later improvement I carried out for Brian G4MEO. I programmed an EPROM with the correct offsets and a repeater shift giving full coverage from 29.310MHz (CH1) to 29.700MHZ(CH40). The circuit is shown here along with the programming details for the 2732


 Also marketed as the LCL2740.

Another radio using the MC145106 PLL. This used a different mixing scheme which required a crystal change to convert to 29MHz.