Most Accurate Clock


Posted on Feb 5, 2014

I built one of these with the RS-232 option many decades ago. It a three channel HF receiver (5, 10 & 15 MHz) that receives either the U. S. or Hawaii WWVH time and frequency broadcasts and displays the time to a tenth of a second. It also has a discipline function that tweaks a 3. 6 MHz crystal oscillator. So it could be called an HFDO, which was available decades prior to any


Most Accurate Clock
Click here to download the full size of the above Circuit.

GPSDO like the Thunderbolt or Stanford Research PRS-10. The PST 1020 is a newer WWV/WWVH clock which is faster to acquire the time. In the photo at the top of the page the clock has just been powered up and is searching for the signal using only the 53" whip antenna. When the speaker is turned on you can hear the signal but the clock is not capturing the data stream. Maybe the signal is too weak, or the receiver needs to be aligned It`s also possible that the "8" digits are an artifact of the camera exposure. Using the HP 8648A signal generator, with the 1E2 modulation option, it`s possible to generate an RF signal at 5, 10, or 20 MHz with either 100 or 1000 Hz modulation (and a choice of sine, square and other 100% AM waveforms). There is an audio file that could be used to AM modulate the signal generator and should cause the clock to display the encoded time. A better way would be to have a PIC micro controller clock that outputs the 100 & 1000 time code data as audio to feed the AM input of the sig gen. Guessing that the problem might be: (1) crystal that`s not too active or (2) a weak Q305 (2N5770) transistor, (3) too close to the bandwidth of the scope or some combination of these. BUT. . after returning them to the original locations testing at 5 MHz showed the yellow data LED will light with 100 Hz modulation and the capture LED with 1 kHz modulation. But after trying 10 Mhz, no luck on either 100 or 1000 Hz...




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