crystal radio: the first real free energy device

[profitis]

Pomodoro:'Surely someone in the 1800s or early 1900s would have tried all of this.'

Doesn't mean records are still available today.plenty underground

[pomodoro]

Pomodoro:'Surely someone in the 1800s or early 1900s would have tried all of this.'

Doesn't mean records are still available today.plenty underground

Someone would have put their findings in a physics journal to beat other scientists to it.  Also, an amplifying crystal diode would have made big bucks before the advent of the vacuum tube in the mid 20s.

[profitis]

Pomodoro:'Someone would have put their findings in a physics journal to beat other scientists to it.'

 better late than never.did you manage to register anything from the doping yet?

[Pirate88179]

Hi Bill
Here's how I would proceed. You are using a design that will be tuned by the air-variable capacitor, right, rather than by tapping the coil.

So go to the coil calculator site you linked earlier. The old air-variables are usually 365 pF at full capacitance. So plug in 930 kHz and, say, 200 pF into the resonant frequency formula and solve for inductance. I get 147 microHenry for the necessary inductance of the coil.

Now go down to the coil calculator and put in your inductance and the radius of the coil form. I put in 147 uH and 0.625 inch radius, and I went to another website and looked up the diameter of #22 bare wire and got 0.0253 inch. For a closewound coil this is the "pitch".  The calculator returned 114 turns, for 2.88 inches of winding length on the form.

So I'd wrap 120 turns of the #22 wire onto the form. This isn't going to be a very high "Q" coil though. For higher Q consider using a larger diameter form, and re-run the calculation. Make two coils, see which works better for you!

I seem to remember that 300 turns on an oatmeal box form works pretty well for a tap-tuned set with fixed capacitance. You can always sand off the insulation along a 'stripe' of the coil and solder a tap or three on there.

The radio will be influenced by other variables as well, so give yourself plenty of room for experimentation. Plug in other numbers for the capacitor, use the smaller wire, larger diameter form, different frequencies, etc etc.

ETA: The photo below is an old tap-tuned crystal set I made a long time ago. The coil is wound on a plastic 35mm film can. The capacitor is 47 pF. The coil has about 140 turns or so. This set actually works pretty well! It does need a good antenna and ground. I have not tried it with the slinky antenna!

TK:

Thank you very much for the info.  I did not know that a larger diameter made a difference.  I will do as you suggested...a good starting point.  I should have looked at the value of the variable air cap but, it looks like a "standard' one that can be purchased on some of the radio sites.  (Not those really good ones that are replicas)  I do have a bunch of litz wire salvaged from an old TV yoke.  I may not have enough for a larger coil however.  I was going to use your slinky idea but, I don't have one at the moment and my challenge is to use what is on hand...and have it work well.  (or at least work, ha ha)

Pomodoro:

Thank you for your input as well.  I appreciate it.

@All:

One can purchase uranium from Bob Lazar's site...United Nuclear.  Also, you can salvage Americium from just about any smoke detector.  I do not mess with any of that stuff.

Bill

[profitis]

Pirate:'One can purchase uranium from Bob Lazar's site...'

Or from ebay,minerals&gemssection