The following is an email message sent out to the PSN-L mailing list regarding WWVB receivers. Last updated 8/23/98 -Larry Cochrane ----------------------------------------------------------------------- Date: 1/13/98 From: Charles R. Patton, Editor, Geo-Monitor The Temic clock part is really a series of three parts of which seem to be the same with only a difference of number of pins in the packaged part. Of interest is that the app note shows two ways to use them with one 60 KHz crystal or two crystals for the IF. In none of the radio clocks I've seen, have they used the two crystal version--only one. Cost, no doubt, but there is a significant improvement in performance with two. As I've mentioned before, the Oregon Scientific "Time Machine" and the Klockit analog movement unit all use the same RF decoder it would appear. However, just before I found out about the Temic chip, I had depotted a Klockit board, and the chip nomenclature doesn't look like it fits the Temic brand. I know Integrated Display Co in Hong Kong builds the Oregon Scientific line, and is big enough to have a custom design done, and since Radio Shack imports a bunch, they may be using the same chip. Be that as it may, Of the units I have examined, the Oregon Scientific and the Klockit and information on one other brand from another experimenter I've talked to, they all have the 4 wire scheme just as Larry describes for the Radio Shack unit -- power, ground, signal out, and inhibit. So if you want to start with something cheaper, get the Klockit unit, it's only $30 and has the same capability--you just have to slice and dice the circuit board a bit to get those four connections -- but it really isn't too hard as the RF section is confined to one end of the board. Be careful about the load you place on the signal out line. The chip runs on only a few microamps, so basically can't drive anything. I would suggest the use of a CMOS buffer (inverter or such) between the data signal and your computer input. I don't know the impedance of the line on Larry's board, but running from 5V will help the driving capability somewhat. I've known about the Temic chips for some time and I'm in the process of building up just boards to be interfaced to the computer. I have 4 samples of the Temic SMT chips in my possession that I got last month, and just got in the 60 KHz crystals last weekend (Digi-Key SE3320-ND cylinder type watch crystals made by Epson for $1.35 each singles). Rather than use ferrite rod antennas, I'm going to use a small loop, which is more available and repeatable and should increase the sensitivity to boot because the effective antenna height of the various clocks is very small because they use such small antenna rods. I'll let you know how it works out when I finish. Charles R. Patton, Editor, Geo-Monitor patton@iinet.com ------------------------------------------------------------------ Date: 8/24/98 From: Larry Cochrane I found this link on making a WWVB antenna and receiver. http://www.lakeweb.com/dbLabs/wwvb.html -Larry Cochrane