2019-05-29 Another Oscillator For AM Band

Also posted part to FB group Building Transistor Radios May 30

I built this coil by winding 20 turns 28 AWG enamel coated wire on a soda bottle cap. It has an inductance of about 17 microhenrys. I wound a tap for the antenna, but it would be more stable if a separate coil with 5 turns of wire was used for coupling the antenna. I used a soda bottle cap for the coil because it’s easy to obtain and the air core inductor has the lowest temperature coefficient so the frequency is very stable. A coil form could be made from a pill bottle, a piece of plastic pipe or piece of wood. I used a push pin to make holes in the plastic for the wires. After I wound it I coated the wires with clear nail polish to make it stable.

I replaced the 27k with a 1k. With the two 3300 pF capacitors, it oscillates at 995 kHz. I haven’t applied modulation to it yet. I’m still experimenting with the values for the 100k resistor and capacitor I drew in series with the coil lead.

My Earlier blog about this is dated May 26. Here is the YouTube video about this with the schematic at the end.

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