Hacking a WWVB Radio Controlled Analog Clock movement.
And build a WWVB Radio Controlled Nixie Clock!

A common example of the Radio Clock movement is designed and manufactured by Quartex Inc, and rebranded for their distributor: Atomix.
They're reasonably priced at about $17.00 each (retail). Providing a low cost method for adding Atomic accuracy to your Nixie Clock project.
I purchased three of these Radio Controlled Analog Clock movements from Klockit, and began an autopsy on one of them. Really interesting!
The installation instructions are shown below, and will help you develop an understanding of their analog clock hand synchronization method.

You can purchase the Atomix Radio Controlled clock movements at local craft stores, or online directly from Klockit

Radio Clock module
From This...
Giant Radio Controlled Nixie Clock
To This!

What is WWVB?
WWVB antenna array

WWVB continuously broadcasts time and frequency signals at 60 kHz.  The carrier frequency provides a stable frequency reference traceable to the national
standard.  There are no voice announcements on the station, but a time code is synchronized with the 60 kHz carrier and is broadcast continuously at a rate of
1 bit per second using pulse width modulation. The carrier power is reduced and restored to produce the time code bits. The carrier power is reduced 10 dB at
the start of each second, so that the leading edge of every negative going pulse is on time. Full power is restored 0.2 s  later for a binary '0', 0.5 s  later for a
binary '1', or 0.8 s later to convey a position marker.  The BCD format is employed so that binary digits can be combined to represent the decimal numbers.
The time code contains the year, day of year, hour, minute, second, and flags that indicate the status of Daylight Saving Time,  leap years,  and leap seconds.
Click on the image above to go to the official U.S. Government web site supporting the NIST stations: WWV, WWVH, and WWVB. A very interesting site.

Begin by understanding how the Quartex WWVB receiver controls the analog clock hands.

Installing and calibrating the original Quartex radio clock movement:

1. Set the hour and minute hand to approximately five minutes before the actual time of day.
2. Install an AA size battery.
3. As the second reaches the 12:00 position exactly, press and release the reset button on the back of the movement. An audible beep will be heard.
4. When the second hand has stepped one second past the minute hand, again, press and release the reset button on the back of the movement. Another audible beep will be heard.
     After the second pressing of the reset button, the second hand will begin double-stepping, two seconds at a time; to indicate the hands are set and the receiver is "seeking" the time.
5. While the second hand is double-stepping, you may press the reset button again to activate an audible beep synchronized to the transmitted signal. It will go silent after 20 seconds.
    This helps you to determine the best location (orientation) for the radio receiver, to ensure it will be able to successfully receive the signal.

A. An on-off beep every second (similar to a heartbeat) indicates good signal reception. And your clock will set itself to the correct time within 24 hours.
B. A static beep (intermittent), or a continuous tone indicates poor signal reception, and a new location must be used.
C. No beeping generally indicates no signal reception at all.

So what did I just do?
After installing the movement into a suitable enclosure, all three hands will need to be manually aligned to 12:00, and then set to just before the approximate actual time.
The movement requires synchronization of the clock hand positions with the receiver. The clock hands do not have an index position to locate them at a "known" value.
This hand synchronization is accomplished during a startup procedure when you insert the battery. The instructions describe the sequence when to press the reset button.
After the battery has been installed, and the second hand has started stepping along, the owner is instructed to press the reset button when the second hand reaches 12:00.
Now, the second hand position is "known" relative to 12:00.   As the second hand passes over the minute hand, the owner is instructed to press the reset button again.
And now the minute hand position is "known" relative to the second hand position. Resulting in synchronization of the movement motor to the receiver/decoder circuit.
To indicate the receiver is "seeking" the signal; the seconds will begin incrementing at what appears to be two steps every two seconds.    Actually, the motor output is
sending a series of two pulses spaced by 250ms, and then waiting the remainder of the two second period. Later returning to a 1pps output when the signal is acquired.
The shortfall with this design is that there's no automatic teaching of the hour hand position; you must manually preset the hour hand position when installing a battery.

How does it work?
Two independent time bases are operating in the circuit. One (the WWVB receiver/decoder), receives the time code information from a 60Khz AM signal via the ferrite
antenna, and that value is compared to the stored analog hand positions taught at startup. The second time base is actually a simple quartz clock movement that can be
either accelerated or decelerated by the receiver/decoder circuit. Note that the clock motor cannot be reversed; only decelerated until the actual time of day is achieved.
If the actual time of day is greater than 30 minutes from the minute hand position, then the motor will be accelerated to synchronize to it.   Likewise, if the actual time
of day is less than 30 minutes from the minute hand position, then the motor will be decelerated until the actual time catches up to the slowed minute hand. Slick huh!

How can I use it in my Nixie Clock project?
If your Nixie Clock design is based on the customary 1pps signal from a crystal or 60hz line frequency,  you can use the WWVB radio receiver hack described here.
Implementation is very easy once you understand how the hand synchronization procedure works, and apply it to your clock circuit design. No special tools needed!

Here's how we synchronize the receiver in a Nixie Clock application:
First; a timer circuit is used to initiate a reset (mode sw) pulse a few seconds after the power up of your Nixie Clock. Concurrently, a separate pulse is sent to reset
the seconds and minutes display of your Nixie Clock to zero.  The zeroing is the same sequence that tells the receiver/decoder that both hands are reset to 12:00:00.
Another timer begins, and waits for the first occurrence of the one-minute decade counter output being set. When the one-minute out becomes set, the MCU timer
program will pulse the mode sw high again.   Again, the same sequence that tells the receiver/decoder that the second hand has reached the minute hand's position.
A shortcoming of the nixie clock adaptation is the actual time could be many minutes away from the reset to zero time, and may take up to 15 minutes after the signal
acquisition to synchronize the minutes display if the actual time is slightly less than 30 minutes away from the displayed time, and the clock is slowed to synchronize.
The reset timer program was written for use in the Microchip 12C508A MCU.   This is a small 8 pin OTP MCU, and requires no external components for operation.
You're welcome to use the 12C508A program under condition that it is not used for commercial purposes. Download the ready to program WWVB.HEX data here.

Click on the image below to view the detailed modification procedure.

Figure 1

Figure 1 represents an image of the Quartex movement removed from it's enclosure.  The antenna is shown in the cover, and the pcb has not been modified.
The two large square pads (with short wires attached) are where the power supply connections were made. The pad to the left in this view is positive 1.5vdc.
1PPS signal out, is a TTL pulse used to drive the Nixie Clock. The Mode SW is actually the reset input, with a simple transistor circuit added for buffering.
Click here to view the modifications made to the Atomix (Quartex) Module PCB done in a step by step sequence, providing nine images commented in detail.

How do I make those interesting looking colon supports that mount in between the tube pairs? Click here to download an image of the colon support.

Clock logic schematic
Example clock schematic with counter reset and 1pps inputs. Click on the schematic image to download the example.pdf file.

The circuit schematic of the Nixie Clock shown above is closely based on an original design by  Mike Harrison.
  I used much of the logic portion of Mike's clock circuit as a Nixie clock example for the WWVB receiver hack.
Dual transformers are used for isolation purposes, and safe construction. A 9vac wall wart powers everything.

 The Quartex receiver functions nicely from regulated 1.5vdc delivered over a 120" phone wire.  The clock circuitry powers the WWVB receiver.

Here's an image showing my Radio Controlled clock after assembly. It was designed to use GIANT Z568M Nixie Tubes made in E. Germany.
The base is cut from two pieces of Walnut, then sandwiched to create a stepped platform. I added a fitted clear acrylic cover for protection.

big clock front

Another view looking down from above.
big clock above

Overall clock error is less than 100ms from the WWVB clock transmission. This clock automatically adjusts for daylight savings time, and leap seconds.
For an idea of it's size; the circuit board is 14 inches long, and four inches deep.   The Nixie tubes themselves stand four inches above the circuit board.

 Are you fascinated yet?,   see the world's first Nixie Tube Wristwatch.  An amazing, humorous nixie creation in a field of it's own...
nixie wristwatch

click on the image to visit the nixie clock and wristwatch site.


Jeff Thomas
Resonant Instruments LLC


This site was last
updated 01/19/04