Wirless Telegraph or CW transmitter

[D.J.]

Hi everyone,

I haven't been here for a while, been studying alot but now I want to build something and I need a little help.

What I want to build is a wirless telegraph, or a CW transmiter, not sure what name to put on it.

Basicly a simple circuit that I can see work. I have tried to build the Basic RF Oscilator on Tony's Site, it didn't work. The signal in was just me pushing a push button very fast, I guess it didn't work.

Does anyone have any ideas, I assume that I would need to build an RF Oscillator that was tunned so that it would be recieved on the lower end of my FM Radio. Then I could hear the change in static when I turned it on.

Any help is appreciated

Thanks

 

[stevez]

Are you just trying to demonstrate a mode of communication? Share a little more of what you are trying to accomplish and maybe we can help.

Amateur radio publications and websites have tons of this stuff.

Googling on "cw transmitter" yeilds quite a bit of simple circuit info on the first page or two. Most of it is confined to the HF (below 30 mHz) bands. Much above that and stability becomes a problem with simple circuits. Keep in mind that most of these require an amatuer radio license. If your plan was simply to demonstrate or improve your skills you could construct the transmitter and operate, so to speak, into a dummy load. The dummy load converts the RF to heat though some leakage may allow it to be heard on a nearby receiver. A non-inductive resistor (50 ohms is normal for a transmitter output) is a dummy load - a light bulb (what they used to use) is not. Mouser sells non-inductive resistors that are fairly inexpensive.

If you were to make a low power (legal) FM transmitter you might provide a tone input rather than a microphone - and key the tone if you want to use CW as a mode of communication.

If I am not mistaken there is a low frequency experimenter's band where no license is required (here in US anyway) as long as you follow the rules.

 

[D.J.]

Thanks for the reply.

I don't rely care about the frequency regulations, I just want to build a simple CW transmitter that I can see work, so their isn't going to be any big range on it.

Refering back to the Basic RF Oscillator, I forgot to put the 1K resistor on the emitter of the transistor so I did that, but I still can't tell if it works or not.

On my radio I can just barely hear a whistling sound when my circuit is on, but that may be me hearing things becuase I want it to work :lol:

I did the google search and all I could find where circuits with mics. I just want something, that I can turn on and it send a CW, then after I test it with my radio, I can build a reciever that will work for it.

Can someone post a schematic for a RF oscillator, that is trigered by a switch and not a mic.

Thanks again

 

[audioguru]

Why not make a transmitter with a microphone and use the microphone so you can tune the transmitter and radio to the same frequency?
Then if you don't want the microphone remove it.
If you want to turn the circuit on and off put the key in series with a battery wire.

 

[D.J.]

Thanks AdioGuru

That's probably what I am going to try.

When you speak through the microphone it makes a frequency, so I though that if a circuit uses a mic then I couldn't just replace it.

I got more work to do

 

[stevez]

There are also various circuits and kits for low power AM broadcast transmitters. These might be less tricky than something up at the FM broadcast frequency. Frequency is determined by coil and capacitor.

I'll IM something your way.

 

[D.J.]

Thanks

If the frequency is determined by the the coil and capacitor
(parellel)then how come I can't build a simple LC reasonace oscillator, for a transmitter.

Thanks for everyones help, I really appreciate it, I would just like top see a simple circuit work :wink:

 

[audioguru]

Maybe you didn't build it with a tight layout on a pcb. At such a high frequency as 100MHz FM, any piece of its wiring longer than a few mm adds capacitance to detune its frequency. I built my FM transmitter on Veroboard (stripboard) and it works fine. I used a very tight layout of its parts.
Many things change the tuned frequency of a 100MHz coil:
Its wire size, total length, length of its wires, inside diameter, outside diameter, number of turns, the spacing of the turns and the capacitance in parallel with it.

A microphone or music source on an FM transmitter doesn't cause it to make a new frequency. The audio just causes its RF frequency to swing above and below its tuned frequency a little. The swing is at the rate of the audio and is called Frequency Modulation (FM). Very loud audio causes a 100Mhz frequency to swing from 99.925MHz to 100.075MHz. With no modulation the frequency is 100MHz. With the microphone disconnected the frequency will remain at 100Mhz.

 

[rigdoctor99]

CW TX RX

I would recomend a search on google for 'Ham radio+home brawing'

You should find all you need to answer your questions:

**broken link removed**