KEA - GPS derived Audio Time Code Generator



[Tone] KEA is a "freeware" DOS program that uses a PC and GPS (with 1PPS) to provide an audio time code similar in sound to WWV. The audio pips are within 1 millisecond of UTC, which is better than most shortwave receptions - no "speed of light" delay issues! A simple code has been added to the pips to aid in identifying hours and minutes as well as seconds. The GPS must provide the NMEA sentence GGA for the software to function.

The PC decodes the serial "numeric time data" from the GPS and so can calculate what the "next" epoch will be. Preparing in advance, it can beep (using internal speaker on PC) and present the time on the screen without any delay at the next 1PPS transition. Thus the time on the display and pips can be used as precision time markers. It combines the 1PPS data and the serial data into an audio form that you can treat as you would WWV type radio reception. Unlike shortwave reception, the pips are always clear, no fading or variable ionospheric delays or interference.

KEA is a companion program to KIWI, they share the same wiring requirements. However the KIWI program is more suitable to time "single events" where the PC will give the time to the nearest millisecond of a manually or logic activated input. For events spread over time, KEA offers "time pip" generation suitable for adding to recorded audio tracks that are later analysed to determine the time of events.

KEA was initially designed for Astronomical Occultation timings. Occultation's occur when a celestial object passes in front of another (usually a star). The timing of this event can be used to obtain size and shapes of Asteroids and topography of our Moon. Many other applications, experiments and research may benefit from KEA.

Requirements: KEA was compiled as a 16bit DOS application, requiring DOS 3.0 or above. The PC does not have to be state of the art, any old pc/laptop AT and above is okay, even a 20 MHz '286' 15 year old AT can easily meet the 1 msec spec. KEA can make that old "junk" PC suddenly have a purpose in life!

As a DIY hobby project it should take an "evening" to put together. A GPS (with 1PPS is required), these can now be purchased for about US$25 on the surplus market. The program does require some electronic skill to connect the GPS and PC, so please read documentation first to see if you have the required skill.

The program should not be run from a W9x/ME dos window, the accuracy is "ruined" by the W9x/ME operating system not giving enough CPU cycles for the application to meet spec! To use the program from W9x, you must click on "Start" and "Shut Down" to "restart in MSDOS Mode".

Because the program does not save any data, it could be loaded onto a (DOS) bootable floppy disk, and so be used on any PC clone, regardless of the Operating System on the hard drive.

Why KEA? (pronounced "key ah") It is a very comical alpine parrot that lives at high altitude in the Southern Alps of New Zealand. It has a shrill piercing call (that sounds just like its name). Because this program "squawks" the time, and the author is also from New Zealand - it seemed an appropriate name.

Installation

Copy KEA (ZIP File) to a new (any name) directory on your PC. Unzip contents (produces 3 files) and read the file README.TXT for further information.

Support and Additional Information

KEA written by Geoff Hitchcox, Christchurch, New Zealand, South Pacific. 

Here are the Menu options of KEA

      1 = Show the Logic Level of 1PPS
      2 = Show the RS232 Serial Data from the GPS
      3 =
      4 =
      5 =
      6 = Conduct Averaging of Latitude/Longitude
      7 = Generate Time Code

      0 = Quit Program (also ESC Key)



Protocol of the Audio Pips.

       Pip = Seconds marker
    Hi Pip = 10 second marker
 Short Pip = 55,56,57,58 second marker
Double Pip = Minutes
Triple Pip = Hours (24HR)  -  lo freq if Hr = Min

59th second always silent


Explanation of the Hour and Minute Coding.

Let's assume the time is 12:09 (HH:MM)

During the minute starting at 12:09

The pip at the  9th second will be replaced by a "double" pip
The pip at the 12th second will be replaced by a "triple" pip

Thus:

On the HOUR the first pip is a double (because minute = 0).

Thereafter each Minute starts with a long pip (like WWV).

If the hour and minute are the same (08:08) then a much
lower frequency triple pip is given.

Midnight UTC is marked by a low freq triple pip (because HR = Min = 0).

No indication is given of the 59th minute, because the 59th second
is ALWAYS silent.

An added Leap second will give 2 triple pips.

CAVEAT: The program works on the following assumptions. That the GGA sentence describes the time of the "previous" 1PPS transition. That not too many NMEA sentences are enabled, that would cause the preceding statement to be false. The software checks that the GPS has a valid fix before starting, it will then run continuously. If the GPS cannot make a valid fix, this will be advised on the screen. Because the 1PPS only requires tracking 1 satellite, the audio output can be assured. If the GPS briefly loses synch to every satellite, it is assumed the GPS thermally compensated quartz will continue to give accurate time stamps - this may be receiver dependent.

The software may not be bundled with any commercial product!

It was designed for use by amateurs wanting the best for least!

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