On Sun, 19 Oct 1997 09:51:29 -0700 Brooke writes: >I would like to build a clock based on the time code from WWVB >(not a TRF type receiver that uses the carrier). I am looking >for an IC that outputs the time code so that I can use a PIC to >then drive either an LED or LCD display. Start with a conventional shortwave radio reciever. Unless you want to recover the 5 or 10 MHz carrier frequency there is no need to do anything with the RF part. The time code is a 100 Hz subcarrier with on-off modulation at I think 1 second or 1/2 second periods. It comes out of the AM detector as a 100 Hz audio signal. The receiver may filter most of a 100 Hz signal out of the speaker output. You may need to modify it for more low frequency response or take the signal output from a point inside. The first stage of processing would naturally be a 100 Hz bandpass filter. It should have about 10Hz bandwidth to follow the modulation. An MF10 switched capacitor filter would work well. Follow it with an envelope detector and lowpass filter. A slightly better design would use another filter with very tight bandwidth so it "rings" at the 100 Hz carrier frequency and drives a synchronous demodulator. You could also try a PLL. All these designs may need AGC. Unless you live in Fort Collins, Colorado, there will be times when no WWV signal reaches you. I don't think there are any chips dedicated to this purpose. It is easy enough to use conventional op-amps or whatever you prefer to process a 100 Hz signal though.