Frequently Asked Questions about Radio Time Sync
ClockWatch Radio Sync time synchronization
works by using a WWVB receiver that is connected to your computer.
Beagle Software has designed a software interface to turn your computer into a
network time source.
Here are some frequently asked questions about
radio time reception.
How does it work?
Radio Sync contains a specialized receiver and
decoder to convert the broadcast. A highly accurate one-pulse-per second output
is provided to Radio Sync from the WWVB receiver. This rising edge of
the signal is synchronized to the the start of each WWVB second.
How accurate is radio
What type of hardware do
The only other requirement is a functioning
with an available serial (COM) port.
Do I need an Internet
connection to use WWVB?
I already have a WWVB
receiver; will Radio Sync work with it?
Why would I want to use WWVB for time synchronization?
Time syncing using WWVB is a good alternative for remote or highly secured computers. ClockWatch Radio Sync does not require an Internet or modem connection.
WWVB time synchronization may potentially be more accurate than syncing over the Internet or by modem. The true accuracy depends on the receiver as well as the computer. Beagle Software's experience is that the Radio Sync when used with the supplied WWVB receiver is consistently accurate within 0.1 second.
WWVB radio-controlled clocks should be able to work in most places in North America. The red areas on the coverage maps below show where a WWVB radio-controlled clock should be able to synchronize. Note that the red area is largest at night, and smallest in the daytime
Coverage at 06:00 UTC
(click on the map to see a larger image).
This coverage map is based on a field strength of 100 microvolts per meter, which in theory should be a large enough signal for most receivers to work with. In fact, the Radio Sync receiver has much better sensitivity (50 microvolts per meter).
Therefore, use this coverage as a rough indicator only. We have heard from many owners of radio-controlled clocks whose clocks do not work inside the coverage area shown on the maps. This is probably due to a local source of interference. We have also heard several reports from Alaska that the clocks work fine, even though Alaska is outside the coverage area shown on the maps. This is probably due to the low amount of radio background noise found in a sparsely populated area.
Map and data from NIST
The radius of signals broadcast by the US Atomic Clock do
extend into Canada in some limited locations close to the
US-Canadian border. ExactSet clocks will not work in Europe where
a different standard is in use.
The IRIG-B from the Model TL-3 is suitable for remote display driving, magnetic tape recording and many other uses. The IRIG code provides Universal Coordinated Time (UTC) or local time in a 24 hour format. IRIG-B Code Format.
The amplitude modulated, serial format of the IRIG-B is divided into three segments. The first segment encodes time-of-year binary-coded-decimal (BCD) notation. The second segment encodes control functions. The third segment sometimes encodes time-of-day in straight binary seconds (SBS) notation. This segment is not encoded by the TL-3.
These three segments are contained within one "frame". The frame length for IRIG-B is 1 second long and contains 100 "elements" (pulses) each of which starts every 10 milliseconds. An element may represent either a binary zero, a binary one, a reference marker or a position identifier. A zero is 0.2 of the duration of an element, a one is 0.5 of the duration of an element and a position identifier or reference marker is 0.8 of the duration of an element. A reference marker locates the beginning of each frame and a position identifier marks the end of every ten elements. IRIG-B has ten position identifiers per frame.
The elements prior to the position identifier P5 comprise the time-of-year segment. The first ten elements encode the seconds, the second ten elements encode the minutes and so on through days. Each element is a digit in a binary number with a place value sequence 1-2-3-4.
Two flags are encoded in the control function segment of the IRIG-B code. The first flag encoded at element P5+40ms is the LOCK indicator. It is a binary 1 when the unit has exceeded the time loss interval of the TL-3. When the second flag encoded at element P5+90ms (Time Quality #4) is a binary 1, the error has exceeded +/- 500ms.
On the TL-3 receiver, the output of the IRIG-B is a 3.5 mm
miniature phone jack where the tip carries the signal and the body carries the
Radio Sync Product Information: