Wednesday, January 13, 2010

500kHz source operative

That's what I soldered together today...

74HCT04 using pins 3 and 4 for the oscillator (1M feedback, 10k damping, 3 legged ceramic resonator), pins  4 and 11 shorted for pulse shaped output on pin 10. Resulting in a 4.023MHz carrier (draaggolf! - now you know what the blog is named after).

SN7493AN: input on pin 14, set to 4 bit (short between pin 1 and 12), pin 10 (!) for GND, pin 5 (!) for +5V and pin 8 for Q2 (divide by 8). Up to now, NOTHING, and that is good!

Keying is done by enabling the ripple counter by grounding either MR1 or MR2 (pins 2 and 3 - inputs of a NAND).
This keying does not produce any audible chirp. At least it did not chirp today ;-)

The near future will add a 74HCT240 as driver and a pulling (FSK) network to the ceramic resonator. Together with an IRF510 HexFET PA, the first attempt of TXing on 600m will be on its' way. Hopefully this will be done by the end of this week!

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