Coiless AM

Never see a coilless radio transmitter. It's rather not possible cuz at such frequencies even short track on pcb is a coil itself and start resonate with nearest capacitor. Very frequent a track are used as coils in short wave transmitters or are hidden inside IC cuz can be mniaturized almost without limts. Some amators build resonant tank wraping one emailed wire around second one this create large capacitance and huge inductance in form of turns . Typically 4-5 turns are enough and u have tank in one. A phase shift oscillator is very unstable cuz not rely on physical resonant phenomenon whose is natural form to stabilize anything. A vien bridge oscillator is much much better to be used as rc generator and actually was used. But rc oscillators are more problematic in design cuz rc feedback crete so high loses that very precise design must be performed to make such thing not lose all feedback signal until it reach transistor base. And must be taken into accout that it need after it have so much power to feed base current. A jfet transistors or rare small signal mosfets are much better cuz not create this damping in form of base current. Also due to rc damping a considerable voltage gain must be performed by transistor typically around 20-30 cuz it need to restore signal and make it little larger to establish positive loop.

If u want to build a wien bridge don't forget it also need a temperature stabilizing in form of ptc thermistor or.... ordinary incadescent bulb lol a Hewlett- Packard wien bridge test generator sold commercially was stabilized just by bulb whose also light up frequency scale.

Yeah ive read about these kind of oscillators. They use the bulb's hysteresis to initiate the oscillations, yeah that would be simple enough. Cant a temperature stabisitaion be otained just by a nice big heatsink and a small DC fan?. The power supply should be pretty stable with the LM78xx series. Hm so I would need a vien bridge oscillator. So what about the mixer? Would this mixer do the trick (the one in this circuit). Also I presume an ordinary amp should be used increase the modulation depth,thats not a problem. What about the detector an ordinary AM radio should do the trick?

And please if someone knows what are the non prosecuted AM frequencies in Europe (especially Bulgaria). That would really help the rest I can figure myself (i still have the analogue circuitry notebook from 10th grade lol :D)

http://cdn.instructables.com/FD3/8QHU/GIKL42D3/FD38QHUGIKL42D3.MEDIUM.jpg theres a coiless am radio too.