Dilshan R Jayakody’s Web Log

HD-1410 is quite popular iambic keyer which is manufactured around the 1970s by Heathkit . The original HD-1410 keyer is designed using 5 commonly available 74LS series TTL ICs and 8 transistors. Other than iambic operation it has an option to adjust sidetone frequency and support for (external) single-paddle key unit. In this project, we redesign the original HD-1410 electronic keyer with today's commonly available components. In this new design, the key components which we replace are transistors, diodes, and power supply section of the original HD-1410 circuit. Most of the NPN transistors in original design are replaced with KSP42 and KSP10 transistors, and all the PNP transistors are replaced with KSP92 transistors. To keep everything simple we also use the same TTL chip-set with this new design. PCB of modified Heathkit HD-1410 electronic keyer. Tested PCB layout for this new keyer is available in the project archive and this PCB layout is based on standard through-...

This is simple Colpitts oscillator to test commonly available passive crystals which range between 2MHz to 27MHz. This unit must connect to an oscilloscope and/or frequency counter to get the frequency of the crystal. This circuit is designed to work around 9V to 12V DC power source. Both 2SC930 transistors can replace with any high-speed NPN transistor such as 2SC829, 2SC933, etc. Testing 5030kHz FT-243 crystal using a prototype version of crystal tester. In our lab, we use Manhattan-style layout to prototype this crystal tester and it produces highly accurate results with an above-specified frequency range. According to our observations, after 27MHz, the amplitude of the waveform starts to decrease steeply. Schematic and Stripboard wiring layout for this crystal tester is available to download in here .