Built this Direct Conversion RX called ASH-DCR. I named it myself 🙂 as it is designed by VU2ASH OM Ashok Joshi. It is a very simple design and a good first project for SWLs entering the homebrewing bandwagon. It mostly uses readily available components and nothing is hard to find. For coils in VFO and Band Pass Filter 10.7 Mhz IFTs can be used without any modification. The Double Balanced Modulator has two Trifilar windings which can be wound either on Binocular TV Balun Core or a toroid scavenged from a broken CFL Lamp.
The Bypass filter shown in the circuit is not part of the PCB layout and I have built it on a separate PCB. The VFO and BPF capacitors are selected for the 7Mhz or 40M Amateur band, these can be easily changed for 20M band. VFO is based on varactor tuning and I have used BB109 varactor diode which is available in most of the components shops for around Rs. 10/-. A 10 turn 10K pot is used for tuning. Also the Audio amplifier uses a LM380 IC and is very loud with a speaker (I have only left a headphone jack due to space limitation in my box).
PCB Layout for the Receiver
Some pictures of my homebrewed ASH DCR
Small toroids from a CFL lamp can be seen on the left of the blue pot in above picture. Also the BPF is above the blue pot.
This box was lying in the junk in my shack. Such tin boxes are very useful to cut down on RFI in sensitive circuits like these.
If you have any suggestions or questions, write to me in the comments section below !
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