Electronics > RF, Microwave, Ham Radio

Mid 1970’s iambic keyer CMOS DIY design

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wn1fju:
I built a similar keyer while I was a poor, starving grad student, sometime between 1975 and 1979.  I don't remember where I got the schematic, but it had to be either from QST or the Radio Amateur's Handbook. 

I had nothing in the way of tools or expertise.  The construction was done on perf-board with point-to-point wiring (mostly with bare wires!!!).  This was a memory keyer and used an Intersil IM6518 1024x1 SRAM.  If I recall, the memory IC cost more than all of the other parts combined.  It was originally battery powered, but at some point I added a jack on the back panel for an external DC power supply.  It had a sidetone oscillator, an internal speaker, and a +/- key output polarity switch, although I may have added some of those features later.

I haven't used the thing in decades, but I just powered it up and it works fine.  It was always a bit annoying to use the memory function, however.  You flick the run/load switch to load, send your message, then flick it back to run and the message will play out whenever you hit the red button.  But there was no provision to stop the loading of the 1024 bits, so after you keyed in something to load, you had to wait until the chip loaded itself with "blanks" until it reached the end.  And you had better key your characters in with perfect timing.  It usually took a few tries.

Kjo:

--- Quote from: wn1fju on December 18, 2021, 01:47:04 pm ---I built a similar keyer while I was a poor, starving grad student, sometime between 1975 and 1979.  I don't remember where I got the schematic, but it had to be either from QST or the Radio Amateur's Handbook. 

--- End quote ---

Nice assembly!
Back in 1975 I wasn't so good at construction techniques. But if all the wirewrap connections hold up it still works!
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Kjo:
Shamed into putting the keyer in a real box!

wn1fju:
Nice job!  I guess these things are for nostalgia nowadays.  Almost every modern transceiver includes a built-in keyer.  But it fun to reminisce.

Kjo:
@wn1fju
Yea, that is true, as my uBitX has one too. But adjusting is more hassle than the dedicated keyer. But nostalgia is the real reason. I still have the 1975 dual paddle home made key as well!
Ko3y

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