An Instructograph

While I was rummaging around through the club’s storage room yesterday, I came across an old Instructograph machine. I’m not sure how old this particular unit is, but it looks like it has definitely seen better days.

Instructograph label
Instructograph label
Instructograph
Instructograph
Instructograph
Instructograph

It’s a paper tape based Morse code trainer with the Morse code encoded as holes in the paper tape. Along with the Instructograph were nine tins containing other tapes. Seven of them were rusted closed so I didn’t try to force them open. A couple were left open, including the one already on the Instructograph.

Instructograph tape tins
Instructograph tape tins
Instructograph tin
Instructograph tin
Open instructograph tin
Open instructograph tin

The Instructograph is essentially just an automatic straight keyer with an audio oscillator. As the paper tape moves between the contacts, the key is closed where the dots and dashes are punched out of the paper and generates the tone. The tapes are double-sided, so when you finish playing one, you just flip it over, thread it back onto the machine and play the other side.

Instructograph contact switch
Instructograph contact switch

I think the tape speed would have been controlled using this lever on the panel.

Instructograph speed control
Instructograph speed control

No idea if the Instructograph still works or what kind of condition the innards are in. The paper tapes are in somewhat delicate condition and I’m not sure if they’d hold up to much playing anymore if the Instructograph did work.

Morse code at 25 wpm

For a while now, I’ve been listening to Chuck Adam’s (K7QO) code course. It’s a good, methodical course that first takes you through each letter, with a cumulative test after every second letter. You get lots of practice hearing each letter by the time you get to Z. I’m starting to recognize most of the letters up to K now.

The course sounds like it’s recorded at somewhere between 15-20 wpm. For most people that’s probably plenty fast enough but it’s just slow enough that my brain still wants to count the dits and dahs and then convert to the corresponding letter rather than just listen to the rhythm of the sound.

What I needed to do is convert or generate a new set of files that plays the code faster. With a bit of experimenting at lcwo.net, I found that 25wpm was where my brain stopped trying to count dits and dahs, letting me focus more on the sound of each letter.

A little bit of searching brought me to a program called ebook2cw by Fabian Kurz/DJ1YFK, who also happens to be one of the people behind lcwo.net. From there, it was a trivial exercise to feed the answer files from Chuck’s code course into ebook2cw to generate a new set of audio files (OGG turned out to be about half the size of MP3) at a character speed of 25wpm and effective speed of 15wpm.

Here’s the shell script I used to generate the OGG files

#!/bin/sh
for file in *.txt
  do /opt/bin/ebook2cw -O -p -o `basename -s .txt $file` $file;
done

Do this in the directory where you’ve extracted the text files from K7QO’s answers file and you’ll end up with a bunch of .ogg files. Then copy them to the media player of your choice (if it can’t handle OGG files, it’s time for a new player). If you insist on MP3 files, just drop the -O parameter. The file names will have some trailing 0’s tacked on before the extension (chapter numbers automatically added in by ebook2cw) but it doesn’t affect anything.

Mini code practice oscillator

I’ve been wanting something small and portable that I could carry around with me for doing Morse Code practice. The Heathkit HD-10 oscillator is fun to play with, but kind of big and chunky to haul around. The ARRL code oscillator is small and portable, but the buzzing sound gets kind of unpleasant to listen to after a while.

Then I found Jason’s/NT7S schematics for his code practice oscillator (CPO) in his blog and decided to build one. I gathered up the pieces and tried to assemble it on a breadboard a while ago but got distracted by other things and never quite finished.

With the acquisition of some solderable mini-breadboards from SparkFun and the perma-protoboards from Adafruit, it was time to get back to the project. The Sparkfun mini breadboard fits perfectly on top of one of their modular mini breadboards so I put the solderable breadboard on top of the modular breadboard and started laying out the components. Then, once I’m done all I have to do is carefully lift the solderable breadboard off the modular breadboard and then solder away.

After spending some time staring at the schematic and the breadboard pondering how to lay things out, I remembered a suggestion from the kit building forum at the ARRL Centennial Convention. Build modularly and test as you go so that if something doesn’t work, it’s easier to isolate the problem area.

With this in mind, I started with the power section of the schematic and laid that out in one corner of the board. Add power, flip the switch, LED comes on. Perfect!

The CPO is small and simple enough so that the rest of the circuit pretty much falls into place after that. After a few hours of placing components, double checking placement and debugging, I finally managed to get it working.

NT7S Mini-CPO
NT7S Mini-CPO

NT7S Mini CPO
NT7S Mini CPO

With a few wires, I connected my straight key and connected straight to the plug of some ear buds I had lying around. Tapping on the key yielded some pleasant sounding tones, and turning the pot changed the volume (and frequency a tiny bit).

NT7S Mini CPO connected to the straight key
NT7S Mini CPO connected to the straight key

Now all I need to do is solder everything into place, add some jacks and stick it into an enclosure.

A nice, easy build and I was able to do it all with parts I had on hand.

Connecting the straight key

After going through the manual for the HD-10, I learned that the terminals on the rear of the HD-10 could be used to attach a key. So off to the garage I went to put some terminal connectors on some wires to use to hook up the J-38 key to the HD-10.

It took a couple of tries before I figured out where the wires were supposed to go on the J-38. There are lots of pictures of J-38 keys on the internet, but not too many that show how the wires are supposed to be attached (the terminals are the two on the inside).

J-38 straight key and HD-10 keyer
J-38 straight key and HD-10 keyer

With everything connected, tapping the key made the keyer make noises and I managed to make some Morse Code sounding noises with the key. Now they can sit on the desk next to me so that I can practice tapping out Morse Code whenever I feel like.

I still need to take the key off the base and clean it up a bit, and then make up a cable that I can use to plug the J-38 into the radio with. Also thinking about seeing if I can find a nice block of wood to attach the J-38 key to for a more solid base and to elevate the key a bit.