Tuesday, 1 May 2012

Updated DC Receiver

Some changes from the original receiver:
1. Uses the latest multiband vfo with +15 to 19dbm
2. replaced the LM386 amplifier with an NE5532
3. a single copper clad was used with separate pcb for the 100db audio amplification

Some notes:
This comes out as 4rth rebuild since the SA612 to diode bridge. The amplification seems a bit low I can barely hear weak stations. There is still a few spurious whistle, but very low volume, mostly are external interference and compared to the LM386 implementation the hum is barely noticeable. I can connect the receiver to an external amplifier and not much hum is heard. There is currently no filter installed and the hope is by adding a 300Hz high pass filter will further remove the hum. This will also be test bed for learning about CW and SSB audio filters.

Variable Air Capacitors and Feed through Capacitors

Always been doing VCO because I had no variable capacitors.