Synthesizer For Sw Reciever

Q EN 811 820 . 122 C28 C20 72132 70p 770p SP 8794 5V BFR 91 =J3 032 = wi= wron 1002 8V ,Cot?, C2 ■I DI. 02: BB 109 008H C213 MIN 7)On • The synthesizer shown in Fig. 1 is computer controlled, and outputs a local oscillator signal (LO) between 48 and 78 MHz for driving the mixer in the SW receiver proposed on page 00. The circuit is based on the Type MC145156 synthesizer from Motorola. This IC is rela- tively inexpensive, and ensures good LO suppression in the receiver when used in combi- nation with a good mixer. Also of interest is its serial control input, which enables the output frequency to be programmed from a computer. The internal reference fre- quency, 1200 Hz, is obtained by dividing the signal from oscil- lator T5 T6 by 2048. The DAC connected to the output of the first LO gives a resolution of 1200/2555 Hz. The divider composed of IC1, IC2, IC3 and Ni has a prescale factor of 2 SP 8691 03 N 1 = / IC5 = SP 1664 SP 8604 MC 145156 BF 256 C BF 982 2475,6F, 108 1N E8441...