QEX

C4 0.0015 polyester 0 2N2222A U4 555 timer U5 4024 counter U6 4013 D flip-flop U7 4030 quad XOR gate U8 1458 Dual op amp

22 k

C4 0.0015 polyester 0 2N2222A U4 555 timer U5 4024 counter U6 4013 D flip-flop U7 4030 quad XOR gate U8 1458 Dual op amp

22 k

Fig 6—NRZI-to-Bi4> assembly mounted on a 2V* x

33/4-inch pert board.

Fig 5— Schematic of the NRZI-to-Bi4> assembly.

developed for the "Microsat Demodulator" described in September QEX. The simple variable-width pulser test device coupled to the NRZI-to-AFSK converter assembly works flawlessly. It allows, as an example, evaluation of multiple bit configurations as related to filter time constants. Another advantage is that it eliminates the annoyance of PTT breaks that are part of the TNC test method.

Summary

Although there is some similarity between this project and the "Microsat Demodulator" described in September QEX, there are enough differences to make it an interesting project. I know of no better way of understanding the system than to build the hardware and make it work. Besides, the uplink is a necessity if you can't resist the challenge of DX digipeating using a low-orbit satellite.

Was this article helpful?

0 0

Post a comment