Propositions for small CW keyers?

[neazoi]

Hi, I want to build a small keyer, to on/off key the final stage of my 100mW HF transceiver.
I would like it to be made with discrete components, yet have the ability to be controlled from the sound level of the sound blaster as well as the com/LPT ports and also manually, using the same plug (preferably a stereo mini jack).
At the past I have designed a similar circuit **broken link removed** which worked, but I would like to add a simple means of shaping the envelope to avoid key clicks. Is it enough to add a capacitor from the base of the BC547 to the ground for this purpose?

Also any other ideas for such keyers would be appreciated.

 

[chuckey]

The contacts of RLY1 does the actual carrier switching so the circuit downstream of the contacts must be filtered.
Frank

 

[neazoi]

The contacts of RLY1 does the actual carrier switching so the circuit downstream of the contacts must be filtered.
Frank

You are right.
I will probably transform this circuit, to use just the transistor and not the relay (electronic switching).
The collector will be connected to VCC and the emitter to the circuit that needs to be keyed (keyed vcc of the circuit).
Is a base capacitor to the GND enough to shape the keying, so no key clicking occurs?

 

[neazoi]

The contacts of RLY1 does the actual carrier switching so the circuit downstream of the contacts must be filtered.
Frank

I did the electronic switching as said, but the output voltage from the emitter is only about 4v.
What should I do?

 

[chuckey]

Your 4V comes from the emitter, so the base of the BC547 must be at 4.8V. You will need two transistors to overcome this problem. If you use one, you can get your 12V change but it will be upside down! So you need a second to get it back the right way up.
So what does the keying voltage do?, it sounds if it might be easier to modify this to go on/off with the 4V.
Frank

 

[neazoi]

Your 4V comes from the emitter, so the base of the BC547 must be at 4.8V. You will need two transistors to overcome this problem. If you use one, you can get your 12V change but it will be upside down! So you need a second to get it back the right way up.
So what does the keying voltage do?, it sounds if it might be easier to modify this to go on/off with the 4V.
Frank

Allright, in other words, I will use this 4v to switch on another transistor. I see..

 

[neazoi]

The contacts of RLY1 does the actual carrier switching so the circuit downstream of the contacts must be filtered.
Frank

The electronic switching circuit did not work as expected. The voltage drop was unacceptable.
I decided to switch to the relay circuit posted at the beginning of this post, which works ok.
You mentioned the thing about the contacts of the relay that affect the keying clicks.
Is there any way to prevent this? A capacitor connected somehow to the relay contacts?

 

[chuckey]

In principle that's the idea, its value and possibley a resistor will be determined by the actual keying circuit used. One problem causing clicks is bad power supply regulation. When the key is up (no RF , low power consumption), the power supply voltages rises and when the key is put down the voltage falls.
Frank