This is an interesting Morse keyer from a very active time in Ham Radio.

Curtis Electro Devices was started as a side business by John Curtis, K6KU around 1968. His full-time job was as at early IC-maker Signetics.

The first keyer product was the EK-38, released in 1969. The -38 indicated John’s age at the time. The EK-39 was released in 1970 and added a ‘weight’ control, adjusting dash length to dot length (with 50% weighting as standard). Also, while the EK-38 had ‘dit’ memory, the EK-39 added ‘dah’ memory as well. The EK-39 was so successful, John Curtis quit his ‘day job’ at Signetics and concentrated on designing and selling morse keyers.

Later the EK-39M added a custom call-sign memory allowing up to 3 stock messages to be factory customized at purchase. The memory was ROM and not programmable after purchase.

The EK-39 is made up entirely of Signetics DTL technology ICs:
* LU380A (3) – Quad 2-Input NOR gate
* LU370A (2) – Triple 3-input NOR gate
* LU387A (2) – Quad 2-Input NAND gate
* LU322B (1) – Dual J-K Binary Flip-Flop

A good reference for Signetics UtiLogic DTL products is the 1969 Databook which can be found on bitsavers.org (PDF file).

Connecting the keyer to a rig is problematic. The straight key input is a regular 1/4″ Mono plug. However the Iambic keyer input and output to Rig connections are unfamiliar to most today.

Normally we use a 1/4″ Stereo plug from our Iambic keyers. Output to the rig is usually an RCA jack, or a 1/4″ Mono plug.

Here, both connectors are Amphenol 80-M Series connectors.
The single output to rig is an 80-M 1 (microphone, in-line cable plug) is used to plug into the provided 80-C connector. This 1-pin male connector is not hard to find. Sometimes referenced as part 80-MC1M. Modern parts are part of Series 91 ‘legacy’ connectors.

The Iambic input is an 91-M 3-pin connector (or, part 91-MC3M). Note that two of the pins are closer and oppose the 1 ground connector. These are more difficult to find, and expensive, running US$40 up to US$100. Keep an eye out at hamfests.

Both of these connectors are sturdy, metal connectors with screw coupling.

Finally, I cannot remember where I got this manual, but it no longer exists in search engines. I’ve assembled the separate pages into an EK-39 User Manual (PDF).