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Help me modify simple HF TX

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neazoi

neazoi

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Hi, this is a simple HF TX (it's core) that I have found in an old HAM magazine.
It outputs about 5-7W depended on the band (160m-20m or so).

I do not like the fact that it uses PNP transistors for the oscillator and that it keys the oscillator. Also the RFC must have a 30R series resistance, so it is critical.

Can you help me modify the circuit to overcome these drawbacks?
 

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neazoi said:
and that it keys the oscillator.
Click to expand...

I once read that a morse transmission should have 'soft' start and end of beeps. It is less jarring than the effect of sharply turning On and Off. Therefore keying the oscillator may be desirable, since it starts up from idle each time. Notice the capacitor in parallel with the key creates a softer shutoff.
 

To avoid "chirpy" signals, you need to key a buffer stage, and not the oscillator stage.

 

vfone said:
To avoid "chirpy" signals, you need to key a buffer stage, and not the oscillator stage.

Click to expand...

Thanks so much! I will try this circuit, although the 2n2222 seems less powerful than the original oscillator transistor. I will see how it goes!
Have you got the ltspice file?
 

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