john@spectre.unm.edu (John Prentice) (06/08/91)
[ everything here, three layers of machines up, has had the OS or the NEWS software updated over the last couple of weeks and I am unable to post (tho news is makeing it in),- John is posting this for me from UNM. Please respond back to the net or mail to the address given below. Reg.C ] I have seen a number of articles mentioning CHU clocks over the last several weeks, along with a new CHU Streams module for SUNs. So, the question IS:---- (1) Does someone build and sell (for a reasonable price) a CHU radio/modem ?? (2) Has someone posted plans for same to the net ?? (3) How about hints, suggestions, whatever, I dont really want to reinvent the wheel... (4) Is this a candidate for a FAQ list ??? Reg.Clemens clemens@afwl.af.mil -- John K. Prentice john@spectre.unm.edu (Internet) Computational Physics Group Amparo Corporation, Albuquerque, NM
mrapple@quack.sac.ca.us (Nick Sayer) (06/08/91)
john@spectre.unm.edu (John Prentice) writes: >I have seen a number of articles mentioning CHU clocks over the last >several weeks, along with a new CHU Streams module for SUNs. >So, the question IS:---- >(1) Does someone build and sell (for a reasonable price) a CHU radio/modem ?? No. Not yet, anyway. With the CHU support in xntpd, there's really not much to the hardware part. I am working on a small CHU clock that will take the raw modem output and make an LED display and a more trustworthy serial output. I'll get back to the net about it in a year or so when I'm done. :-) >(2) Has someone posted plans for same to the net ?? I did, but here it is again. See below. >(3) How about hints, suggestions, whatever, I dont really want to reinvent > the wheel... There's not much to it, really. >(4) Is this a candidate for a FAQ list ??? It's getting there. If anyone at WWV is listening, how about finding ten seconds per minute for a sane timecode? Five seconds? :-) Here's how to build a CHU modem in 4 steps: 1. Power. From the DC jack, the + line goes to the a 7805. The - line goes to ground, and to the ground pin of the 7805. The output side of the 7805 is the power supply bus for the whole rest of the project. Place a 100 uF capacitor between the input side of the 7805 and ground, and another between the output side and ground. Place an LED and a 220 ohm resistor in series across the output side of the 7805 as well. This LED is a power-on indicator. 2. Preamp: From the audio input jack center conductor (shield to ground), to once side of a .01 uF capacitor. The other side of the capacitor goes to one end of a 10 k-ohm pot. The other end of the pot goes to ground, and the "sweep" on the pot goes to pin 3 of the LM386. Pins 2 and 4 are grounded, pin 6 goes to 5v+, pin 5 goes to the + side of a 220 uF capacitor. The - side will simply be called "point A" for now. It's the output of the preamp. Now the gain of this section can be set one of three ways: for 13 dB gain, 17 dB, or 23 dB. For 13 dB gain, do nothing more. For either 17 or 23 dB, connect a 100 uF capacitor between pin 7 and ground. For 17 dB gain, put another 100 uF capacitor in series with a 1.2 k-ohm resistor between pins 1 and 8 (the + end of the capacitor points towards pin 1). For 23 dB gain, replace the resistor with a piece of wire (leave the capacitor). 3. RS-232 conditioning: Connect pin 16 of the MAX232 to 5v+, pin 15 to ground. Put 22 uF capacitors between pins 1 and 3 (+ to 1), 4 and 5 (+ to 4) and 6 and ground (+ to ground. Yes, + to ground). Pin 14 goes to pin 2 of a DB-25. Pin 7 of the DB-25 goes to ground. It might be a nice idea to put some RF-chokes on the wires going to the DB-25. I simply choked the RS-232 cable. Pin 11 goes to "poing B" for now. 4. The modem. Now the meaty part. The MC145443P: Pin 1: NC Pin 2: ground Pin 3: see below Pin 4: a .01 uF capacitor to ground Pin 5: "Point B" in section 3 above Pin 6: 5v+ Pin 7: A .1 uF capacitor to pin 19 Pin 8: A 3.579545 crystal to pin 9 Pin 9: the other end of the crystal Pin 10: A .1 uF capacitor to pin 19 Pin 11: 5v+ Pin 12: ground Pin 13: 5v+ Pin 14: 5v+ Pin 15: A 470 ohm resistor to pin 16 Pin 16: A 470 ohm resistor to "point A" from section 2 above and the resistor from pin 15 Pin 17: NC Pin 18: short to pin 19 Pin 19: In addition to the other stuff, a .1 uF cap to 5v+ and a .1 uF cap to ground Pin 20: NC Pin 3 is a TTL carrier detect output. It goes low on a valid frame. A resistor goes from there to a little transistor inverter circuit that drives an LED. This is sort of optional, but very useful. -- Nick Sayer | Official Scapegoat for the | RIP: Mel Blanc mrapple@quack.sac.ca.us | MC68HC11 Mailing List. | 1908--1989 N6QQQ | To subscribe, send mail to | May he never 209-952-5347 (Telebit) | mc68hc11-request@quack.sac.ca.us | be silenced.