Having concluded that I was significantly short on overall receiver gain, I went in yesterday and changed my AF amp from a 40db direct-coupled circuit to a 100db Darlington pair. I immediately noticed a big increase in audio output.
I did a quick receiver alignment using my Arduino/AD9860 sig generator. First I determined the actual bandpass of the crystal filter: 4.998170 MHz -- 5.000960 MHz. Using a freq counter, I set the BFO at 5.00126. I immediately started hearing 17 meter SSB signals from the West Coast. That's always a nice moment: first signals through a new receiver. Kind of like "first light" in a new telescope. Even with the filter ripple, it sounds great.
I think I'm still significantly short of gain. Audio is still faint. I notice that in the BITX17A they have added a second transistor (Q17) in the second RX receive amp. Maybe I should try something similar. Or should I add some gain in the audio chain?
I'm really enjoying this BITX project.
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"
Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke
Our Book Store: http://astore.amazon.com/contracross-20
The Radio Shack • Re: cheap pocket radios - Do you have a link to an example? Statistics: Posted by Richard — Sat Apr 29, 2017 4:14 pm ------------------------------
2 hours ago