I am trying to build a simple superhet receiver for listening SSB signals. I read several articles about SSB and got confused so I am looking for some practical explanation.
I have 2 mixers, quartz filter between them. So there are 2 conversions. First, from HF to IF, second from IF to audio.
Let's say I want to receive LSB in range 3747-3750 KHz. If I understood LSB concept correctly 3750 KHz will become 0Hz in audio and 3747Khz will be 3kHz. Some sort of inversion. Am I wrong here?
If my intermediate frequency is 8MHz and I have some ideal filter in range 8000-8003KHz what should be first oscillator frequency?
I think like this:
8000 + 3750 = 11750 // I set DDS above the received frequency
so the lower part HF frequency will be on the high side of IF filter
11750 - 3747 = 8003
And second oscillator frequency then has to be 8003 for LSB (highest edge of the IF filter):
8003 - 8003 = 0 8000 - 8003 = 3
And if I had USB I had to set to the starting IF filter frequency (8000kHz).
Am I getting it all wrong? Can somebody give a good explanation with examples? Or good article to read.