Tuesday, 20 February 2018


                                      DIRECT CONVERSION RECEIVER
                This project is the Direct Conversion receiver found in chapter one of Experimental Methods in RF Design. The receiver is set up for the 40 meter ham band which is 7 to 7.2 MHz. Documentation in the book says the unit should receive 6.9 to 7.5 MHz. Once built I will be testing the unit for power consumption, frequency range, and frequency stability.
                Fortunately I got a pcb for 40m direct conversion receiver at hfi 2014 hydrabad from om vu2pti Pradeep Kumar.After went my home I started to build this receiver.I got to buy some torroids(T50-2)  and some components from vu3gek.                                                                                                                            
                                                     HERE IS THE CIRCUIT DIAGRAM

I started to build this circuit first to make L2 and L3 by using T50-2 torroid for 4.7uh.and rest of the parts not changed. After completing the board and connect with 12volts power supply,the circuit will not work.The defect found in the tunned circuit.So I remove the Torroid coil,two varicap diode and 10k tuning control.I make some calculation for c14 and c15.
A thump rule c14=1000/sqrt of.F and c15 = 100/ sqrt of.F where c in pf and f in mhz.
By making resonated formula other capacitors are calculated for 20 turns of coil on sketch pen closed winding will give 2.4uh.i used fm tuning capacitor for tuning and removed (1k) r2  resistor into 200 ohm, zennar diode and leave the pin 2 of ne602 open.I powerd the circuit by 9volts battery.now the circuit works with 3m antenna wire for some stronger signals.there is some drift  after 5minutes. I housed the board in an old tv booster power supply box.the circuit works in excellent and covers 7000khz to 7200khz. Success in homebrew direct conversion receiver.
                                          ASSEMBLED AND HOUSING OF DC RECEIVER