Using CHU broadcasts as a time source
I want to build a "gadget box" like the one describe at the Pulse-per-second Signal Interface page that is part of the NTP documentation. The gadget box would allow me to decode the time signal in Bell 103 (300 baud) standard from CHU, the Canadian National Research Council's shortwave broadcast transmitter located near Ottawa, Ontario, Canada (Google Maps).
The only problem I have is that the one of the two IC chips is obsolete, the MC145443 from Motorola (but would be a part from Freescale now).
After trying to find a source for the MC145443P (Plastic DIP packaging) in small quantities (e.g 1-5) I discovered that Lansdale makes a pin-compatible replacement called the ML145443, unfortunately when I contacted them they did not have any in stock, so they were not able to provide me with any. :-( When I re-read the first page of the Lansdale datasheet for ML145443, I noticed that it mentioned that it was also pin-compatible with MM74HC943, which appears to be the National Semi's version of Texas Instrument's 74HC943 Bell 103 one-chip modem.
I found and ordered a couple 74HC943 chips at Unicorn Electronics, hopefully that will work.
I found what I thought at first was a good choice for a replacement chip, CMX867A from CML Micro via CDI in Ottawa, but after further reading, I don't think so. I might still get a few to experiment with.
Although the MX614 which is in-stock at CDI might be more interesting as the main chip for a 1200 bps (Bell 202) Baycom-style packet modem as described in this January 2000 QST article, Updating the TCM3510 with the MX614 Packet Modem.
I noticed that CDI also carried Mini-Circuits RF parts, I'll have to investigate that later.
At least I can find the ICL232CPE (Plastic DIP) made by Intersil from Newark, but as far as I can tell MAX232 is pin-compatible with it, so I might use the more common MAX232 from TI or Maxim.
If all this fails I'll just plug the headphone jack of my ten dollar shortware radio into my soundcard's mic or line-in jack and use Bill Rossi's CHU Time synchronization for Linux.
BTW gadget.tar.Z can be downloaded from http://www.eecis.udel.edu/~ntp/ntp_spool/hardware/gadget.tar.Z
There is also the idea of going with a soft modem, or even a soft modem in an embedded system, like a dsPIC, since Microchip has a free (gratis) library for V.21 (Bell 103) modems which should run on any of the dsPICs. There is also source for DSPs and I think someone wrote a Bell 103 modem for the 8-bit Atmel AVR.