The classic NE-567 chip makes a fine CTCSS decoder with one major consideration. In a real world circuit the detection band-width is kind of wide, meaning you can and might also experience valid decode logic on the two tones each side of Frequency-Center.
If you construct a well thought out circuit using all the expected considerations for frequency stability and control (voltage regulation and the right type support parts) the 567 will do what you want. There are/were a few commercial 567 CTCSS decoders on the market although it's not normally considered as the first choice. Because some people don't seem to want to read and apply the data sheet information the 567 often gets a bad rap in the decoding sub audible tone department. You'd think CTCSS Detection would almost be a "no brainer" when you want to build something simple and easy... but all the classic land mines will find those who don't read the mfgrs data sheets. I would toss out the idea of using/copying the Yaesu and/or Hamtronics 567 circuits... The Yaesu circuit I have in my archives does both encode and decode using the same chip. cheers, s. > "James" <ka2...@...> wrote: > Hi Guys, > 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. We will set it to 107.2 and the next time you check it is > off enough to where it won't decode until it is re-tuned slightly. I am > wondering what your experiences may have been with this CTCSS Chip. Many > articles say they work well with the addition of a stable voltage regulator, > so we added a five volt regulator, no difference in stability. Any comments > and experiences with this and other chips would be appreciated. The > availability of CTCSS Chips seems limited. >
