OK. I need to build something, now (I got my grab bag and I want to apply what I've learned so far.). I've been reading the books, but unfortunately, when it comes to certain things, like circuit details, they gloss over them or I'm missing something really basic.
I want to take this receiver and convert it to a commercial broadcast shortwave receiver: 4MHz to 20MHz - maybe higher.
I will use a toilet paper roll tube (4.4cm X 10cm ) for a coil base. I will wrap it with 26 gauge magnet wire with tails every 10 turns or so for a total of 60 turns based on the equations here.
I got that variable capacitor to de-solder from a circuit board - I don't have anything to measure capacitance so I was going to (trial and error) adjust the coil to make it work.
As far as the diode is concerned, I have a bunch of 5245BP signal diodes that I would like to use, I have a few NPN transistors floating around and here's where I'm stuck - the capacitor 'C2' It shows 100p in the diagram. How do I calculate the time constant that will be needed for proper demodulation and filtering of the carrier? The time constant calculation is here but how to relate it to the frequencies of the radio? And will I need more than one?
Or for that matter, how does one choose the proper diode?
Any other thoughts, suggestions or comments would be greatly appreciated.
I want to take this receiver and convert it to a commercial broadcast shortwave receiver: 4MHz to 20MHz - maybe higher.
I will use a toilet paper roll tube (4.4cm X 10cm ) for a coil base. I will wrap it with 26 gauge magnet wire with tails every 10 turns or so for a total of 60 turns based on the equations here.
I got that variable capacitor to de-solder from a circuit board - I don't have anything to measure capacitance so I was going to (trial and error) adjust the coil to make it work.
As far as the diode is concerned, I have a bunch of 5245BP signal diodes that I would like to use, I have a few NPN transistors floating around and here's where I'm stuck - the capacitor 'C2' It shows 100p in the diagram. How do I calculate the time constant that will be needed for proper demodulation and filtering of the carrier? The time constant calculation is here but how to relate it to the frequencies of the radio? And will I need more than one?
Or for that matter, how does one choose the proper diode?
Any other thoughts, suggestions or comments would be greatly appreciated.
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