QLF Filter Assembly Procedure
Part 3 - Remaining LEDs and Your First Processed CW
OK! You are on a roll. Now, lets get down to business. It's time to connect the remaining LEDs and the key. Were gonna send some code, with a slightly less than left footed accent.
74LS240-3 to LED1 -
74LS240-5 to LED2 -
74LS240-7 to LED3 -
74LS240-9 to LED4 -
74LS240-14 to LED6 -
87C750-16 to 74ls240-17
87C750-15 to 74ls240-15
87C750-14 to 74ls240-13
87C750-13 to 74ls240-11
87C750-5 to 74ls240-6
Install R10 (4.7K) Connect from +5V to 74LS240-2
Install C2 (.01mfd bypass) connecting 74ls240-2 and GND
Install R11 (4.7K) Connect from +5V to 87C750-7
Install C3 (.01mfd bypass) connecting 87C750-7 and GND
Check your work, or at least admire it for awhile.
Attach a temporary key between 87c750-7 and GND.
Power up the circuit. you should get "ok". LED 1 may be lit.
Try sending some "morse code". Notice that you get exactly what you put in. (And it's probably not that great) This is the TNC input, and no processing is performed on the signal.
Attach a temporary key between 74LS240 -2 and GND.
Power up the circuit. you should get "ok" LED1 may be lit.
Now try sending code. Now, you experience the benefit of the QLF filter. You can send decent code with a crummy key, even a couple of wires touching.
Notice that LED5 blink rate will change as it tracks your sending speed.
As you send, LED2, LED3, and LED4 should light in sequence. This indicates the transition from a dit to a dash. You may find them fun to watch. (maybe)
Send 11 dits in a row. LED6 should light, indicating that your speed is locked. The clock led will remain at a constant blink speed.
Send a dash that is 3 seconds long. The Lock led (LED6) should go out.
Send some really sloppy code. LED1 will come on to indicate you have a left foot instead of a fist!