AM Transmitter

325

04:23:50

Made two new inductors 2uH each and bought an RF choke. Increased the frequency to ~1MHz. Will test very soon. 
Self starts. Give it several seconds. 
Haven't built it yet but most likely will in the future.
I'd eventually like to build something small that I can experiment with on some ham bands. Anyone have some favorite resources, and RF BJT's they'd like to recommend? 

published 6 years ago

hurz

6 years ago

for 100kHz as it is now you do not need special RF BJTs. BTW, the oscillator current is not local inside the oscillator part of your circuit. follow it and you will see it does a long journey throuh your power supply. It circles. You need to block that, best with an RC network in front of the oscillator. In case your PS is a bench supply, your carrier is quickly on the mains power line! Be careful

hurz

6 years ago

Another thing i see is your audio imput is grounded and not capacitor decoupled, why?

hurz

6 years ago

the following class C modulator cuts completely the negative part of any audio. Hmmm. I think you should give it a try till this modulator part an see how good it works. If you have annold radio it should have 100kHz AM on LW

crake

6 years ago

Yeah, I had read about using RF chokes. I'll go ahead and experiment with that.

crake

6 years ago

No good reason for not having the cap. The modulator worked without it IRL so I didn't include

crake

6 years ago

I do plan on trying some version of this circuit. Trouble is I don't have an old radio.

hurz

6 years ago

doesn't need tooo old. even on harmonics you can use MW receiver. third and fifth harmonic should work perfectly 300 and 500kHz

crake

6 years ago

Great idea, hurz thank you. I'll definitely give that a try.

crake

6 years ago

Collpits works great IRL. Having trouble with the class C though. If anyone has some suggestions, study material, etc I'd love to see it. I have found some stuff on EC but I want to read about the theory.

hurz

6 years ago

Class C is meant to be an efficient amplifier, but a modulator hmmmm

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