Tuesday, 1 May 2012
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
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.
|Always been doing VCO because I had no variable capacitors.|