I'm trying to prototype in a circuit simulator and it seems that there is a bug with transistors. Hit the reset button to mess it up. Even when I build one from several sources it gives a similar odd signal. -- I'm trying to building a transmitter so I can virtually demodulate it in the simulator. (Tomorrow I'm going to try this with a 555 timer instead of common emitter AC amplifier)
What I'm looking for
- A very simple AM (DSB) receiver -- eventually for the NIST WWV station.
- Preferably 10Mhz.
- Made of simple and irreducible components.
What I'm not looking for
- Reducible components such as op-amps and 555 timers kinda scare me.
- High fidelity - I'm fairly certain that I can program around noise on my Arduino.
What I know
- The signal is received on an antenna and frequency resonated on an LC circuit tuned to 10Mhz. This "filters" out the unwanted frequencies. The output from this is a carrier wave.
- The carrier wave is put through an
RC circuit (parallel low pass?)Envelope detector to demodulate it into the output to decode on my Arduino.
- 440Hz, 500Hz, 600Hz, 1000Hz, and 1500Hz for tone markers
- There is a 100Hz "subcarrier" that continuously broadcasts "date" information (Year, month, day, hour, minute, and DST to name a few)
What I do not know -- Links & explanations greatly appreciated!
- Do I need any special length for my antenna?
- Can any inductor/capacitor combo be used that meets the LC resonance frequency equation? (C=100nF, L=50.3uH, should resonate at 10Mhz)
- I'm guessing this is tied to the output voltage or current of the antenna. How would I calculate this?
- Would amplification between any step be useful for final input on my Arduino? (Antenna->LC->Envelope->output->Arduino)
- Would I run the output into another LC->RC circuit tuned to get the sub-carrier?
- Does an LC->Envelope circuit even work for dual-side-band? (I honestly couldn't find a difference between normal AM signals and AM DSB)
Bonus: Is there any good free simulation software? (I can't seem to get circuitlab to output any useful simulation graphs, unlike Falstad's "View in Scope" or scope-probe)