HD-1410 is quiet popular iambic keyer which is manufactured around 1970's 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.

Complete technical specification of this unit are listed in below (these information are obtain by original HD1410 specification sheet):

  • Keying output, positive line to ground: Max. voltage open circuit or spikes - 300V. Max current - 200mA.
  • Keying output, negative line to ground: Max. voltage open circuit or spikes - 200V. Max current - 10mA.
  • Audio: Internal speaker or jack for optional hi-Z (at least 500Ω) headphones.
  • Sidetone: Adjustable from 500 to 1000Hz.
  • Internal controls: Sidetone frequency, paddle tension, paddle level.
  • Rear panel connections: AC power cord, 12V power input, keyer output, headphones, receiver audio in, ext. key.
  • Power requirement: 120/240 VAC (±10%), 60/50Hz, 3.5W or 10-14.5V VDC, negative ground, 150mA.
  • Dimensions: approx. 3'' H × 5'' W × 7½'' D.
  • Net weight: 3 lbs.

In this project we redesign 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 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 same TTL chip-set with this new design.

PCB of modified Heathkit HD-1410 electronic keyer.
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 though hole type components. Dimensions of this PCB is 110mm × 102mm.

We test this modified HD-1410 design with several transceivers and it performs extremely well. This new design also behaves similar to original HD-1410 unit and the parameters which got change are DC input voltage range and power consumption only.

Project Related Downloads

Schematic, PCB and wiring diagram for modified HD-1410 keyer unit.


74LS00 - Quad 2-input NAND gate
74LS02 - Quad 2-input NOR gate
74LS10 - Triple 3-input NAND gate
74LS73 - Dual negative-edge-triggered master-slave J-K flip-flops with clear and complementary outputs.
KSP10 - 25V 350mW NPN epitaxial silicon transistor
KSP42 - 300V 500mA NPN epitaxial silicon transistor
KSP92 - 300V 500mA PNP epitaxial silicon transistor
Original Heathkit HD-1410 keyer schematic