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
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
