19 august 2021

Sine wave CW generator with XR2206

 There is a while since I made a nice electronic keyer; being made with Arduino, a simple solution to monitor the keying was to define a PWM pin and to push the signal into a small piezoelectric speaker.

The sound is horrible and many times I thought to make a small one transistor oscillator.

The goal became more acute as I plan to use ICW, an online CW audio "chat", a place where I can train my CW skills with a human correspondent without bothering others on the waves. Fort that, a sine audio generator is needed.

But... I am lazy. The one transistor sine generator is a mess because you need to make a buffer and an amplifier then some sort of audio filter with a bulky coil, you know... And I am lazy!

Being lazy have some advantages. One of them is some sort of visual memory to compensate. Instead of searching or making improved iterations, I lay back and try to visualise things...
I rememberd one time searching for some components and saw in a box a nice circuit, XR2206, a nice function generator. It was in the same box with a XR2211, a pretty nice FSK decoder. It's presence was vivid in my mind because some months ago I tried to make a CW decoder and the XR2211 was used as a PLL detector for the audio CW signal. But that never worked and I abandoned it for the cheaper LM567. But this is another story...

So, I start to search the endless raws of boxes just to find the ... XR2211!!! My mind was in a dead loop... Wait, it must be a mistake! If I have the XR2211 in the box, WTF I did on that PCB???

Now, the search moved into another boxes. The higher tier, those with failed or abandoned projects...

An pretty soon I found the PLL CW decoder with, you guess it, XR2206! Damn, that's why it never worked!!! Not only I am lazy, I am also stupid.

So, now I have the XR2206 on the bench, everything is it place, after 30 minutes, the generator was ready to be tested.

I used a schematic found on the web and I kept only the necessary components for sine wave as square and triangle was not needed. Of course it didn't worked and I had to go to the datasheet to make things like in that document. I kept the things simple.

Here is the schematic:

Because the schematic was simplified, the sinus is not a perfect one, just a "good enough" one.

The next step will be to find a way to switch ON/OFF the sine wave.

21 iulie 2021


 I planned to work HF/portable from Dubrovnik when coming back from Austria but, unfortunately, the change of pandemic rules for entering the country was subbject to a last minute change thus I replanned my trip.

I ended on the Lake Balaton, in Hungary and I spent my birthday there with my wife and my daughter, on a very nice villa with a beautifull view and a balcony that was the perfect spot for my HF portable setup.

I had with me the little Xiegu G90 with some portable HF antennas from which the MP-1 was the "hero".

I managed to work in 20m band some YO stations from Bucharest, Constanta, Timisoara and Brasov and from Bulgaria and on the West side, Finland, Germany and UK.

It was nice but I am a little sad I could not reach Dubrovnik!

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