At 5/7/2010 04:21, you wrote: > > We have been experimenting with building CTCSS Units using the > > 567 Tone Chip and good components, i.e. Caps, multi turn pots etc. > > The stability is not good in my opinion. > >For encoding, there's a million PIC-based solutions on the net. >I designed my own, using a different PIC (12HV615) to reduce >extra components to minimal: it has a built-in voltage stabilizer >(no 78L05 needed, just a resisitor), and using bitstream D/A >so no external D/A network neccessary.
By "bitstream D/A" do you mean PWM? If so, how fast do you clock it & how many serial bits do you use to create each "sample"? >For decoder, check out http://www.mcarcoh.org/ke8rv/photo-sd.html, >specific the comments about his controller. >I exchanged mail with the designer and his design is facinating, >though not publically available, which is understandable. It's really mind-boggling what can be done with PICs. I see Don's using the analog input of a fairly low-end PIC, but I'd think you could use a digital input if the output of the LPF was limited via a very high gain amp. stage, a la ComSpec. Did he implement an IIR filter in the 12F675? Bob NO6B
