Re: The 222 Stereo Coder

by Runem Sat Aug 09, 2014 12:03 pm

Very clever! Never thought of that.
I have proper crystals for Harry's "Stereo Coder" in my parts bin here. Two kinds actually. One hoots at 4864kHz, and the other one at 38.000kHz.
Send me a PM if you're interested. You can have two of each for free if you pay the postage.

have a look in this thread also.
https://sm0vpo.forumotion.com/t89-222-stereo-encoder-modified

by mictester Mon Jul 28, 2014 11:13 pm

Hi

I rummaged around my crystal box, and couldn't find anything like the 4864kHz rock you used. Then inspiration struck.... I dug out a 455kHz ceramic filter. I lashed up a quick FET oscillator, and found that it went at around 458kHz. A little capacitive loading, and I had 456kHz. The signal was big enough to clock a 4017, so that was programmed to divide by 6. This then drove a 4013 to give bi-phase 38kHz from the first flip-flop and a nice stable 19kHz from the second.

So - if you're prepared to use 2 CMOS ICs instead of just one (the 4060) and build a simple FET "crystal" oscillator, you can use a cheap 455kHz ceramic filter as the frequency source for your stereo coder.

One other thing occurred to me afterwards - the 456kHz divided by 8 gives 57kHz for an RDS coder, and will have the correct phase relationship with the 19 and 38kHz......