homemade morse cw practice keyer

[heathtech]

Hi folks,
Maybe someone can help me out. I downloaded a morse code training shareware that requires a cw keyer with a mono jack connected to the mic input of a computer soundcard.
Since I am studying morse, I wanted to build my own keyer. I happened to have an old tone generator that creates a nearly square audible AC waveform at about 810 Hz, which is designed to test speakers. Cheap little gadget that I never use anyway, so I wired up a momentary pushbutton switch to the input, and a mono jack to the output. I plug it into the mic input, and I have a pretty decent practice keyer as far as creating a tone goes. However, for some reason the software is having a very difficult time recognizing the cw. Several possibilities swirl through my head: Does the software require a sinusoidal signal? Is the 3 volts output enough? Is the frequency
inappropriate? Does anyone familiar with this have any ideas?

 

[zachtheterrible]

3v output is more than enough.

When you say that its having a hard time, do you mean that it works sometimes, or it has never worked?

One possibility is that the software is not looking at the right input. Perhaps its looking at line in instead of mic in. Thats just an example, it could be looking at a number of different inputs instead of the right one.

Can you record the sound on your computer?

 

[williB]

3V input to your mic input !!
are you trying to blow your sound card??
use the line input .. and drop the voltage output from your keyer , down to 1V p-p...

 

[heathtech]

OK, sounds like the sound card can't handle 3 volts, didn't know that. (Computer belongs to work, not me) :twisted:

When you say that its having a hard time, do you mean that it works sometimes, or it has never worked

Ok, when I key the switch, The software recognizes the keydown on graphical meter (pegged out), likewise, the unkeyed graph is near 0. I hear the 810 Hz oscillation through the speaker. However, the software is supposed to tell the difference between the dit's and dah's, and print text as you go. If I press a short keystroke, it will ocassionally recognize a letter E. Ocassionally, a longer keystroke will produce a T. this is all very intermittent, with some double E's and hardly ever two letters correct in a row.
Tomorrow I will attenuate the signal and see what happens.

 

[zachtheterrible]

It sounds like you may have blown out the soundcard already :lol:

 

[heathtech]

nah, everything else works just fine, I think I'm going to play around tommorow with a bench freq. counter/generator and see if I can get it to work.

 

[audioguru]

The sensitivity of a microphone input is designed to match the 5mV output of a microphone. When you unkey your tone, maybe you didn't use shielded cable and the connecting wire picks-up hum and noise which the software thinks is continuous keying.
Connecting the very high output of your tone to a line input (100mV) would help.

 

[stevez]

Are you sure the software is looking for a tone? A keyer, by itself, provides contact closure, one or two contacts. You said the input is supposed to be a keyer with a mono jack - implying a straight key or the electronic equivalent which would be something that closes/opens. I don't know if contact closure produces any useful input to a soundcard - just commenting on the keyer requirement.

 

[heathtech]

Heathtech

Audioguru:

Connecting the very high output of your tone to a line input (100mV) would help

Thanks , Audioguru. So I still need to attenuate the input, and connect the generator/keyer to the line input at 100mV. This is obviously a phono pug, with two channels. Should I hook the positive output of the generator to both or just one of the stereo channels, or does it matter?

SteveZ:

Are you sure the software is looking for a tone?

I am not sure, but I am assuming that the audio inputs of the card are isolated, so it would require AC for them to see anything. Can anyone confirm that? I was just working on an assumption there. Like I said before, I am studying morse code in preperation for my Ham license, and from what I understand, Ham operators plug a keyer into the mic input of their radio equipment and communicate with morse by modulationg a continuous wave (CW) audible signal on the carrier frequency , creating dah's and dit's that can be heard at the reciever. I haven't purchases or built any real equipment yet, because I am not going to take for granted that I will pass the test. Therefore, I am working on assumptions, and the freeware software only says to plug a keyer into the mic input, not specifying the characteristics of the keyer. Actually, it did say a CW keyer, which logically implies that the keystrokes generate a continuos wave. I think I am correct. Anyway, I just happened to have a tone generator lying around that I used a long time ago for testing speakers, and I figured it might work if I wired up the momentary switch and mono jack, just for fun and for practicing. The name of the software is CW_Player, for anyone interested.

Audioguru, I don't have any phono jacks lying around, just mono. If I solder the shield wire to the outside conductor and the positive to the inside conductor of a mono plug, will one of the stereo channel inputs on the line input work? In other words, is the phono female jack designed in such a way that a mono plug will work with one channel?

[/quote]

 

[audioguru]

A computer's mic and line inputs are usually a 3.5mm stereo jack, the same as on a portable CD player.
A stereo plug has a tip for L channel, a ring for R channel and a sleeve for 0V and the shield. You can join the L and R to get mono on both channels, but don't short together the channels from a stereo source without isolation resistors.

Yes, if you plug-in a mono 3.5mm plug, it will feed the mono signal to only 1 channel on the mic or line input stereo 3.5mm jack.

 

[Nigel Goodwin]

Re: Heathtech

Audioguru:

Connecting the very high output of your tone to a line input (100mV) would help

Thanks , Audioguru. So I still need to attenuate the input, and connect the generator/keyer to the line input at 100mV. This is obviously a phono pug, with two channels. Should I hook the positive output of the generator to both or just one of the stereo channels, or does it matter?

I would suggest both would be best, and given the choice I'd do that.

SteveZ:

Are you sure the software is looking for a tone?

I am not sure, but I am assuming that the audio inputs of the card are isolated, so it would require AC for them to see anything. Can anyone confirm that? I was just working on an assumption there. Like I said before, I am studying morse code in preperation for my Ham license, and from what I understand, Ham operators plug a keyer into the mic input of their radio equipment and communicate with morse by modulationg a continuous wave (CW) audible signal on the carrier frequency , creating dah's and dit's that can be heard at the reciever. I haven't purchases or built any real equipment yet, because I am not going to take for granted that I will pass the test. Therefore, I am working on assumptions, and the freeware software only says to plug a keyer into the mic input, not specifying the characteristics of the keyer. Actually, it did say a CW keyer, which logically implies that the keystrokes generate a continuos wave. I think I am correct. Anyway, I just happened to have a tone generator lying around that I used a long time ago for testing speakers, and I figured it might work if I wired up the momentary switch and mono jack, just for fun and for practicing. The name of the software is CW_Player, for anyone interested.

Although a radio amateur I've never done morse, it wasn't needed for a class B licence in the UK - BUT, certainly historically, morse involved keying the transmitter carrier directly, just a simple ON/OFF as you pressed and released the key. However, on modern cut down equipment it sounds quite possible that it's been "cost improved", and the morse key inputs left off. In that case inserting a switched tone in to the microphone socket of an SSB transmitter will provide a similar effect (if rather crude?).

I would expct the software to try and detect a tone, as that's what the receiver will provide - in the past it's been common to use an NE567 PLL to provide suitable pulses from the tone output.

Audioguru, I don't have any phono jacks lying around, just mono. If I solder the shield wire to the outside conductor and the positive to the inside conductor of a mono plug, will one of the stereo channel inputs on the line input work? In other words, is the phono female jack designed in such a way that a mono plug will work with one channel?

You could certainly try a mono one, by the way they are called a 3.5mm jack plug, either mono or stereo (not a phono plug).

 

[heathtech]

Thanks, Nigel.

Well, as you were posting, I got it to work just fine. I stayed with the mic input, and added a ten turn pot to the generator output. Obviously, I was overloading the soundcard. The tone is now a nice audible dit and dah, and the software recognizes it. Thanks all.

 

[stevez]

A keyer is connected to the KEYER or KEY input of a transmiter or transceiver - not to the microphone. I do agree that the sound card might not see this but a KEY or KEYER usually is contact closure - hard contacts or electronic. Quite often mic connectors are used -which may explain the misunderstanding. Note that some key inputs are two wire - some are three. If the key input is traditional it will have two wires - one contact closing or opening. The contact closure could come from a straight key, a mechanical keyer (it mechanically generates dits and dahs) or some other device that generates dits and dahs but that are seen as a single contact closure. A built in electronic keyer might want to see three wires - a dit, a dah and a common. This is used with paddles - dit is one way, dah is the other.

CW is an unmodulated carrier that takes up very little bandwidth. CW bandwidth is somewhat related to the keying rate. If you were to "key-in" a tone and the transmitter actually worked the output might sound like CW but would have a much greater bandwidth and has a different emissions designation. Sometimes this "tone modulation" is used with AM, SSB or FM to simulate CW. I think (I'd have to check to be sure) that you would not be able to use anything but real CW in the CW portions of the ham bands.

Keying a transmitter can involve turning the oscillator on and off, amplifiers and buffers - each one is different.

I thought the explanation might help the original poster. Good luck.

 

[Mike - K8LH]

heathtec,

You might like to check out CWType and CWGet software from DXSoft... I believe CWType is free... Use the simple parallel port interface in the documentation for Paddle inputs and you've got one heck of a nice Code Practice Oscillator with iambic paddle or keyboard input...

Regards, Mike

 

[heathtech]

Yes, it does help, SteveZ.
Thank you. So, what you are saying is, that Amateur radios have a keyer input, and the keyer is just a switch contact, with no generator. So, does this mean that the CW generator is built internally into the radio? I learn about new things best when I read or hear about them, then try to figure out for myself how it works, and ask for corrections. Ok, let me ask this...On AM radio broadcasts, a carrier frequency is transmitted when a mic key is pressed, and then voice information (AF) is modulated onto the carrier (RF), amplified, and transmitted, then demodulated by the reciever, turned back into AF, then amplified to a speaker (in basic terms). So, on AM, is the same basically true of CW transmissions? Is the CW modulated onto the carrier? It seems that if it wasn't and just a closed or open contact was all that's involved, that all you would hear is dead silence, like a keyover? Isn't that true? In other words, the carrier frequency is obviously not in the audible range, so there has to be some means of applying AF to the carrier. So, basically, what I am concluding is that even on radios with a keyer input, there must be an internal CW generator which is being modulated to the RF when the keyer is depressed. So, basically speaking, it seems to me that the same thing could be accomplished through a mic input with an external generator. Now, having said that, I am only implying that a practice setup like I have on the computer is working on the same principle that a built in keyer does, I'm just supplying the tone frequency. Am I incorrect? I don't want to be mistaken or mistake someone else. The only difference that I can foresee is that the built in system may still be modulating carrier between keys, where the homemade device I am playing with is disabling the RF in between keystrokes. Have I thought this through correctly?

 

[stevez]

healthtech - I read your last post quickly so bear with me. CW isn't modulated except that it's turned on and off. It is a continuous sine wave at the frequency of interest. Some intelligence can be conveyed by turning it on and off with the listener making the connection between the dits/dahs and what they mean.

If the CW is modulated then it is no longer CW, it is something else. That may seem trivial at this point but you'll soon understand if you keep studying.

In a simple CW transmitter the key is used to turn an oscillator and/or an amplifier that follows, on and off so that the transmissions are CW broken up by the pauses that represent the dit's and dahs. If you were to turn on some AM radios and could tune in and listen you'd most likely hear the dits and dahs but as hisses rather than tones. The tone in a CW receiver is often the result of another signal being mixed with the "hiss" so that it sounds like a tone.

It takes a fair amount of skill with a straight key to get a consistent spacing between all the dits and dahs. People developed ways to improve the sending of morse code by developing mechanical keyers - that helped form the dits and dahs. Eventually they put electronics to work and someone added a second input - so you could close a contact to get dits - properly timed and spaced - and another to get similar dahs. In varying ways they've packaged this magic. Early versions were separate and distinct boxes with vacuum tube (valve) electronics that formed the dit's and dahs - and that closed contacts so that the transmitter didn't know that it's wasn't a key - it just responded as if it were a key. Solid state versions came along and eventually many or most rigs have the key provided internally - most likely indistinguishable from the rest of the electronics in the rig.

As you might guess, a "keyer" question could apply to an old rig, a new one or anything in between. Many practice keyers have a speaker and tone generator - with a headphone jack. I'd bet that the tone generator of a practice keyer is what might serve well as input to the sound card.

Anyway, back to work.

 

[audioguru]

The hams who transmit blank carrier for Morse Code seem to transmit a lot of hum and noise with the carrier. You must watch the signal strength meter to see if there is a carrier or not. :lol:

 

[heathtech]

Thanks All, I have learned a lot! Isn't that always the point?
NEVER STOP LEARNING!

 

[Nigel Goodwin]

healthtech - I read your last post quickly so bear with me. CW isn't modulated except that it's turned on and off. It is a continuous sine wave at the frequency of interest. Some intelligence can be conveyed by turning it on and off with the listener making the connection between the dits/dahs and what they mean.

If the CW is modulated then it is no longer CW, it is something else. That may seem trivial at this point but you'll soon understand if you keep studying.

Applying a 1kHz tone to the mike input of an SSB transmitter won't produce a modulated output, simply a carrier wave (CW) 1KHz away from the set frequency of the transmitter (which isn't transmitted) - which is what I presume happens with a morse tone generator feeding in to a mike socket?.

Also, there's been mention of "watchin the S meter", or trying to hear the "quiet" when the carrier is ON. These are both a load of rubbish :lol: for CW you use a CIO (Carrier Insertion Oscillator), a simple type of which is called a BFO (Beat Frequency Oscillator). This reinserts the original carrier wave from the transmitter and results in an audio tone (for morse) or the original audio (for SSB).

For an example:

Your SSB transmitter is set to 10MHz, and you have a morse key tone generator which provides a 1KHz tone. If the key isn't pressed then there's no output from the transmitter - just as if it's not turned ON. When you press the key the transmitter outputs a plain carrier wave at 10,001,000Hz (10MHz + 1KHz) - assuming upper sideband operation!.

Your receiver is tuned to 10MHz (just like the transmitter) and includes a CIO set to 10MHz - when it receives the 10,001,000Hz signal the two will mix together, and the difference will be the original 1KHz tone. Usually a receiver will be a superhet, and the CIO will be at IF frequency rather than RF - but the principle is exactly the same. Also, direct conversion receivers are popular for home construction, and in that case the CIO is directly at the RF frequency.

 

[stevez]

I agree and disagree. I agree that if you applied 1 kHz tone to the input of an SSB transmitter it should generate the equivalent of a CW output as long as the SSB generator eliminates the carrier (as most modern ones do). I would not agree that the emission classification would be the same though I make no claim to being an expert on emissions classifications. If I get time tonight I'll see if I can find the classification.

healthtech - to add to the confusion on keyers - the mic on my ICOM IC-706 has up/down buttons for frequency adjustment but these buttons can be programmed to function as an iambic keyer - one button for dits and the other for dahs.