On 4/22/2011 4:23 AM, m II wrote:

It's probably been done already, but here goes:

How about making a two part receiver, one stage for the normal detection
and tuning, the other a really wide band receiver with a conversion
portion in it.

Probably an interesting exercise, but not very practical.

That part would collect any and all signals hitting it and convert it to
a very small dc output.

Connect a germanium diode directly to the antenna (no LC, this is your
"wideband" portion). Use germanium because of its .3 volt barrier
junction, not a silicon diode because its junction voltage is .7 volt.
Put a filter capacitor on the output side of the diode.

That in turn could be used to power an amplifier
for the audio of stage one and then work a small speaker.

Surely there should be enough broadcast power over the entire AM band,
that, if collected and rectified, would drive a 2 inch speaker at very
modest levels.

Generally very unlikely that you would get enough power unless you were
virtually next door to one or more AM stations...and in that case you
could possibly drive a speaker (assuming proper impedance matching)
without an amplifier.

Side story: The 50 kW AM outlet of a TV station I once worked for was
actually (dimly) lighting an incandescent lamp in a nearby home that was
located in the main lobe of the directional pattern. People also were
getting shocks from their rabbit ears TV antennas.

Additionally, you have the "inverse square law" working against you.
Example: if you are comparing two stations, one that is one mile away
and one that is 4 miles away, the more distant station would have *one
sixteenth* the power of the closer station.