Ip Ix

Circuit board (top). Fig. 10. Full-size reproductions of PC board.

sistors will function in the clock circuit. A HEP 57 is j good choice. Both germanium and silicon diodes arc used in the diode read-only memory. Germanium diodes are employed fur the and function, since their low junction capacitance will not load the Jk flip-flops in the program counter-Either silicon or germanium diodes may be used in the or function, with silicon signal diodes preferred since they result in a higher noise margin for the memory. Cheap diodes are available from various solid-stale supply houses, !3o!y Paks features 50 silicon or germanium diodes for $ 1.

Both sides of 3 x 5 in. double-sided PC hoard are shown in Tig, 10, A one-sided hoard was used for the first few models.

the construction of this ID generator, the builder should obtain as many of the referenced II) generator articles1"2"3"4 :is can be found and read them over carefully.

he additional background material will amply repay the efforr involved.

T he Seattle repeater group can supply a moderate number of tinned epoxy glass circuit boards for this ID generator. The board is not drilled, but assembly instructions and a computer optimized diode map for the circuit board is included. Be certain to specify the desired code stream, keeping in mind the absolute limit of 32 characters (dots, dashes, and blanks). Unit cost is $10, and they may be obtained from tin* Seattle repeater group, 18235 46th PL S., Seattle WA 98188.

Here s whaf the board looks like when the flaipacks and diode matrix are soldered in. The vertical placement of the diodes helps to keep the size down to this 3 x 5 in. circuit board.

with a second 3 x 3 in. board used to complete the matrix connections. This "cordwood" construction is a pleasure to look at. but a nightmare to wire up. If a diode goes *\vesf on a cordwood style generator, it is best to tiirow it away, since unsoldering about 80 diodes and resistors and then getting things back together is even worse than the initial construction effort, A double-sided epoxy—glass PC board is recommended for the ID generator, An operational generator should be enclosed in a metal box with all leads bypassed for rf\ Even VHF/UHF fields have the ability io drive RTL logic circuitry absolutely crazy. Before undertaking

Acknowledgement. The author expresses appreciation lo K7EVO for art photography, and to K7M\V< for the snapshot.

References

1. A Digital Identification Generator, Barry Todd K6ZCE, 73 Magazine, March 1967.

2. JC Repeater Identifier, Tom Woore WB6BFM, I' M Magazine, January 1969.

3. Automatic CW Identifier John Connors W6AYZ, Ham Radio Magazine, April 1969.

4. A Digital Morse Code Generator, lerry Hall K1PLP, OST, June 1969.

5. Dig/tai Logic Devices; QST, July

6. Micro-Logic for Non-logic Userst Hank Olson W6GXN, 73 Magazine, June 1967,

7. The Micro-Uitimaticf Tom Pickering WICFW, 73 Magazine, June 1966*

8t Logj'ca/ Design of Digital Computers, Montgomery Pliister. John W iley & Sons. 1953.

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