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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.

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


mike



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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.

On 04/22/2011 01:23 AM, m II wrote:
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Hash: SHA1

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.

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


mike

no

mV/m means roughly how much voltage is captured by a 3.3' loop. Note
that next to the antenna a huge station will produce about 2.5 to 3V in
the sampling loop. A long wire antenna would probably capture enough
Volts to drive a transformed speaker, but then you couldn't use a small
signal diode; you'd need something a little beefier.

I have used this technique to build air monitors at stations where
studio and transmitter share a location, but I always use a power amp.

http://www.fccinfo.com/CMDProEngine....97821&sHours=D

On Apr 22, 1:23*am, m II wrote:
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.
There was an article in Popular Electronics in the early 1960s about a
crystal radio that could directly drive a speaker. Two features that
I remember are dual tank circuits and using 1N54A diodes (selected for
high back resistance/low leakage) as a full-wave voltage doubler
instead of one of the more popular 1N34. I don't remember the speaker
being chosen for large magnet size, but the common 5" speakers were
pretty efficient.

http://www.devilfinder.com/find.php?...ilt+in+Speaker

I have an old 120 in 1 kit.Some of the parts are missing, it was like
that when I bought it at the Goodwill store.
cuhulin

On 4/22/11 07:01 , Joe from Kokomo wrote:



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.



When I worked in Iowa, the array was in a cornfield west of town.
A developer bought the land directly north of the array (we beamed
5kw nearly straight north) and built a subdivision there. The back
yard of some of those homes ran up to the fence around the array.

One of the features of these homes was recessed flourescent tube
lighting in both the basement and the garage.

One cluster of 5 homes, not only did the owners get my radio
station on their refrigerators, but the flourscent lights could not
be turned off.

There is, or used to be, a way to use a flourescent light bulb to detect
those speed trap radar guns.
cuhulin

On 04/22/2011 08:31 AM, D. Peter Maus wrote:
On 4/22/11 07:01 , Joe from Kokomo wrote:



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.



When I worked in Iowa, the array was in a cornfield west of town. A
developer bought the land directly north of the array (we beamed 5kw
nearly straight north) and built a subdivision there. The back yard of
some of those homes ran up to the fence around the array.

One of the features of these homes was recessed flourescent tube
lighting in both the basement and the garage.

One cluster of 5 homes, not only did the owners get my radio station on
their refrigerators, but the flourscent lights could not be turned off.


We (KRIZ now KOY 1230 Phoenix)had to read the antenna current at the
doghouse every half hour when I started in radio. We had an F40
fluorescent tube we used at night to light up the meter. We only ran 250
Watts at night so we had to get the bulb right next to the feed wire to
get it to glow. Then we could move it a few feet away.

You can see the modulation in the lamp. That's kind of cool.

If you drive around town with a tube type flourescent light bulb sitting
on the dashboard of your vehicle, see if it will start glowing.
cuhulin

On 4/22/2011 10:11 AM, wrote:
If you drive around town with a tube type flourescent light bulb sitting
on the dashboard of your vehicle, see if it will start glowing.
cuhulin


Take a fluorescent tube to a "CB Shootout" where everyone is running
multi-kilowatt linear ... you'll actually feel the warm glow!

ROFLOL

Regards,
JS