Pickard crystal radio not working

[davidmumford]

I bought Borden Radio's Pickard crystal radio kit, assembled it with my grandson, hooked an antenna to the roof and pounded a pipe into the ground. Something amiss, don't even get static. Antenna is 18 gauge steel wire, about 10 feet high, 50 feet long, but with longish connectors to radio, and in a forest. Grandson wound the coil backwards but don't see why this makes a difference. My car radio gets some half dozen AM stations, some better than others. Kit has a brass rod to connect to coil at variable points after sanding off the enamel coating, fixed capacitor (120 pf). "Headphone" is a one ear type high impedance crystal plug. Connections are wire to screw, not soldered. What to check to show what's wrong? Growing up 75 years ago, I made one using a crystal diode that worked great and I wanted to show my grandson that the air is full of invisible signals and explain AM to him.

 

[betwixt]

Looks like they do several kits, all of them grossly overpriced. Which one do you have?
Can you post a photograph of your construction for us please.

Brian.

 

[D.A.(Tony)Stewart]

- use a beep or ohm test for continuity on wiper as you slide it end-to end. It should be continuously conducted.
- check with a magnifying glass that the magnet wires are clean copper at the point of contact and clean between strands with a brush.
- If no sound or noise on the Xtal earpad check the crystal contact. If you have a Schottky diode try that.

The ohm test on the earpad should be a loud audible click.

I don't recall a ground wire when I was 12, 60 yrs ago when my Dad made a pickle jar radio. None of the houses had a ground outlet and protection with an MOV would add too much capacitance, a TVS maybe.

My Merc SUV has terrible AM reception in Toronto.

 

[dick_freebird]

I had a crystal "spy pen radio" from the back of
Boy's Life magazine when I was a kid with an
allowance that wouldn't buy one battery. It did need
to be clipped to the radiator fin (handy ground, the
up-north hydronic heating plumbing) to get any signal.

A "true" crystal radio, cat's whisker and galena detector,
would need the operator to scratch around until a "hot
spot" was found - a point-contact II-VI Schottky diode
spot had to be hit just right, to not be ohmic or "dead"
(crystallography matters, invisible to the eye).

Present day it's more likely a germanium or Schottky
discrete part but not knowing the particular kit, maybe
it's real old-timey and actual galena nugget (I have once
seen a kit that way).

 

[betwixt]

If it is one of those kits with a spring contact wiping across the inductor, the results will never be good. At least one and probably several turns of the coils are shorted to each other by the contact so the 'Q' will be very low.

I have experimented here for fun with a crystal radio. With a fixed inductor and variable capacitor (far more sensible than variable inductor), a germanium diode and an additional inductor/capacitor ATU, I can dimly light an LED from its output when tuned to a 5KW AM transmitter about 11Km away. Not a practical home lighting solution but interesting to see how much can be harvested with such a simple circuit.

Brian.