A Brief History of the Micro IDer

David Pointer of Urbana Computer Works and Stephen Look of Monticello Micro got together to write an article for 73 Amateur Radio Today, published in the January 1994 issue. Steve designed the IDer and Dave designed a programmer for the Xilinx XC1736A serial PROM used in the IDer. Very few hams have access to a programmer for these unusual parts. Unfortunately, shortly after the article was published, Xilinx discontinued the XC1736A. Its replacement, the XC1736D, works the same, but is manufactured with a different fab process requiring a totally different programming algorithm and voltages, rendering all of Dave's hard work obsolete! He still has a few left, if you wanted one as a base for a microcontroller project, he can make you a deal! The Micro IDer, however, is still alive and kicking. These tiny units have been carried to the edge of space in numerous balloons, launched atop rockets, have been fox-hunted, and see service in many remote (as in wilderness) beacon sites. Their low power requirements and small size make them ideal for these applications.

The Micro IDer is 1.6" x 0.6" and weighs less than 0.5 gram. Voltage can range from 3-6vdc at less than 2ma peak current. Even a 3v coin cell will power the Micro IDer for many hours!

Theory of Operation

The Micro IDer is based on the Xilinx XC1736D serial PROM (U2). This eight pin IC will store 36,288 bits of data. When a clock signal is applied to pin 2, each bit in the memory appears at pin 1 in sequence. This pin is connected to the base of transistor Q2 to drive the keying circuit of a transmitter. Q1, R4, and R5 form an inverter between pin 6 and pin 3. When the last bit of the memory has been clocked out, the PROM generates a logic high at pin 6. The inverter applies a momentary logic low to pin 3. This resets the PROM and the entire memory is read out again. Timing is provided by a CMOS 555 timer.

mkid - a Morse Code Compiler - With the large memory space available, two programs were written to simplify message generation. Create an ASCII text file of the message you wish to be sent. All characters are supported but not the prosigns. Two other characters are supplied to add a solid tone and silent pause function. A pound sign "#" in your text file will generate a solid 1 second tone. Place as many of these in a row as you want for the duration of the tone. An exclamation point "!" in your file will create a 1 second period of silence. Again, string as many of these as you want together. Use a carriage return where ever you wish, they are ignored. Upper or lower case is ok. A very simple example is:

KA9SZW BALLOON #####

This would create a Micro IDer that would send the KA9SZW call, space, "balloon", space, and a solid tone for 5 seconds. Long tones are good for DFing balloons. This is all you need to know to order an IDer. Instructions are on the disk if you want to homebrew your own IDer.

Above prices include S&H, even to Canada! Hi Guys...

The circuit board alone is available from FAR Circuits, 18N640 Field Court, Dundee IL 60196 for $3 plus $1.50 S&H. The programmer circuit board is $11 plus $1.50 S&H. Illinois residents get stuck for 6.25% sales tax for any of the above - sorry.