How does a Morse Key operate?

S

skedmi

Member
Hi, I'm a musician interested in recording a morse code for a piece of music. I'm looking to purchase a morse code key to make it as geniune as possible. Really old sounding with static noise.

I've been looking around in ebay to purchase one, but I don't really know what I'm looking for. I'm seeing many morse code keys that doesn't seem like they can make any sound because there's nothing attached to it.

What I would like to know is, what should I be looking for? How does this thing work?

Also, how can I refine my search so that I will get that right old sound from it? Meaning, a specific year or a specific technology, or model?

Thank you.

Shy.
 
Hiya Shy! :)

Morse Keys by themselves are nothing more than a switch. Some may look very elaborate, some are very expensive (the rare ones), but even the best is still a switch!

The 'tone' that you hear from a short-wave receiver is the result of mixing two signals together, one is the off-air signal, the other is locally generated within the short-wave receiver itself. The resulting mix produces the tone that you hear, normally between about 600Hz up to about 1000Hz (D5 to C6 approx.), depending upon the preference of the listener. The tone, due to the filtering action of the receiver, is nearly always a sinewave.

To be quite honest, if you are not going to 'send' any Morse for real, you can download lots of various free Morse Code training software that will generate the code sound you require on any PC. Also, these Morse Code trainer programs very often allow you to type in a message and the PC will convert the text into Morse Code characters automatically. Just do a Google search for "Morse Code Generator", or "Free Morse Code Training Software" etc.

Some of these programs can also generate simulated 'atmospherics' and signal fading etc.

If you have a keyboard synthesiser handy, some of them can be set up to generate pure tones, or perhaps you may have a guitar effects unit that can be 'persuaded' to produce a sine-wave like sound.

If you don't have access to a short-wave receiver, you could always use a medium-wave or long-wave broadcast receiver, and tune to a spot on the dial where there are no stations and record the 'atmospherics' from there. Night-time is generally best for the noises you are after.

By using either a synthesiser, or a Morse Code program, a broadcast receiver, and a simple mixing console, you can fool any listener into thinking they are hearing 'retro' Morse Code broadcasts.

Morse code when listened to on short-wave, tends to gently fade in and out in strength (Radio Hams refer to this as QSB), so you might like to slowly fade up and down the volume of the Morse Code tone to add extra realism.

If you just want any old Morse Code signal off air, then take a look around YouTube. There are loads of Radio Hams who have posted films of the stations in action, and many feature Morse Code.

If you do really still want to use a real Morse Key, then you will need some way to generate the tone. Look around eBay etc, for a "Morse Practice Oscillator".

By the way, a company called MFJ make a unit which combines a Morse Key and the tone generator all in one item. It is called the MFJ-557. Even brand new they are very often cheaper to buy than the cheapest second hand Morse Key on eBay!

Hope the above 'ramble' helps!

Best 73, Mark.
 
Hey Mark, thank you for the detailed explanation.

I eventually didn't wait for an answer and decided to try my luck with a morse code key that looked promising because it had a cable. It is a J-38 model if it helps.

Just as you said, it is appearantly just a switch. I tried to plug the cable into a guitar amplifier and nothing happened.

You say that I need a "Morse Practice Oscillator" in order to make the key to make a sound. Is that where I plug the cable into?

Thank you again for your help, you've made things much clearer.

Shy
 
Hi again Shy

Yup, a Morse key is just a switch.

There are two ways you could use your key:

1) To turn the power on and off to a small buzzer circuit etc.

2) To interrupt a continuous audio tone from some other source, i.e. connect up the key so that the signal from the tone source/oscillator/syth has to pass through the key contacts. When the key is 'up' you will hear no sound, when the key is 'down' it will make the connection between the audio source and you amplifier/tape etc.

If you use a guitar with a good sustain unit then one pluck of the string should give you a 'tone' for maybe a minute or two, more that enough for some Morse code. Or maybe a synthesiser with one of the keys held down. You get the idea...

Early Morse code generated by spark transmitters had a rough, raspy sound to it. You can get a very similar sound from old door buzzer units. Just connect your Morse key across where the door buzzer button is an hey presto, you have olde worlde sounding Morse.

Best 73, Mark.

p.s. the J38 is quite a good key - good choice!
 
Thanks once again Mark, I would have no clue otherwise.

I went on ebay and bought a Code Practice Oscillator, I hope to get it on the forthcoming days. I'll post another message here to tell you whether this quest was successful or not. I'm sure it will.

Thank you for all of your help 😊

Shy
 
Hi Mark - I wanted to thank you once again. The oscillator arrived and it sounds great! Everything works. I only thing I would wish to have is an option to make the frequency of the taps higher. I have a knob, but it takes it as high as C#5 (above middle C) and as low as G4 (also above middle C). Do you know of any way that I can make the frequency higher?

When I just turn the oscillator on, the bip is higher and then it stabalizes on the set frequency of the knob. That happens only when the tubes are cold.

Anyways, it is not critical, that C#5 works fine.

Thanks for reaching out.

Shy
 
Hiya Shy

I like your code practice oscillator. You could change some of the component values to alter the pitch of the tone produced, but, as the unit is a tubed one you have to be very careful about what you do.

The main concern I have is that if you were to touch the wrong component inside the oscillator then you could end up receiving a nasty shock! Some tube units run at 350 Volts or more, so I would say to you what I say to customers over here; If you need to ask then you probably aren't competent enough in electronics to carry out the work safely.

Depending on the design used, you may only need to change one component to achieve your aim. Two things you could do, one is to seek out the help of a local Radio Amateur or Amateur Radio store, tell them what you need and see if they can help.

Alternatively, you could seek out a music store that carries out repairs to tube amplifiers, and again ask them if they could modify the oscillator for you. Any repair technician worth his or her salt should be able to carry out the mod easily.

Sorry I can't help you more...

Best 73, Mark.
 
Oh, you did more than enough!

Thanks for the heads up. I think I'll keep it this way for the meantime and try to record it as it is. If I'll decide to make any changes I will ask someone who knows how to deal with it to do it.

Thank you!

Shy
 
Another thought did come to mind Shy, if the pitch or frequency of the Morse Code tone produced by your Morse Code practice oscillator is to low, you could alter the playback speed to increase the frequency.

Even the simple sound recorder that used to be in Win98 (and possibly XP etc,) had a facility to increase the playback rate by about 25% steps.

If the frequency of the Morse tone was too low, you could always record the tone at a rate much lower, then speed it up to whatever you need.

Or looking at the problem the other way around, if you have an exact pitch or frequency in mind, use an instrument to record a short sample of that note (using the sound recorder I mentioned or something similar), and then play it back at a slower rate while taking note of what percentage you have slowed down the recording.

While playing the note at the reduced rate, adjust the tone from your Morse practice oscillator to match it, then make a Morse code recording at that pitch but play it back at a rate increased by the same percentage that you slowed down your wanted note.

You should then have a Morse code recording at the correct pitch for your music recording.


Best 73, Mark.
 
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