I have been pondering this idea of using catwhiskers to connect to
multiple 'hot spots' on a giant galena crystal. Note the very small
galena crystal used in a crystal radio that does not require a battery,
uses a high impedance, 2,000 ohm earphone.
What if each of these catwhiskers are feeding into a high impedance
load, that in turn is feeding into a low resistance, deep dielectric
capacitor bank, maybe using the ultra-capacitors?
Of course each catwhisker has to be tuned for the maximum output as we
aren't looking for quality of sound, just quantity of current flow
(billionths of a watt???).
Leads to the idea of a 'tuned rock' to run your house...<g>...maybe even
hook up a phase locked loop to keep it automatically correcting the tune
to sustain the greatest output, of course, that would take more than the
hot spot could provide....crawl before we walk..ok, got it..sorry...
Good overview of impedance;
http://www.shure.com/app-impedance.html
What is impedance? Impedance is how much a device resists the flow of an
AC signal, such as audio. Impedance is similar to resistance which is
how much a device resists the flow of a DC signal. Both impedance and
resistance are measured in ohms.
For audio circuits, is it important to match impedance? Not any more.
In the early part of the 20th century, it was important to match
impedance. Bell Laboratories found that to achieve maximum power
transfer in long distance telephone circuits, the impedances of
different devices should be matched. Impedance matching reduced the
number of vacuum tube amplifiers needed which were expensive, bulky, and
heat producing. In 1948, Bell Laboratories invented the transistor - a
cheap, small, efficient amplifier. The transistor utilizes maximum
voltage transfer more efficiently than maximum power transfer. For
maximum voltage transfer, the destination device (called the "load")
should have an impedance of at least ten times that of the sending
device (called the "source").
This is known as BRIDGING. Bridging is the most common circuit
configuration when connecting audio devices. With modern audio circuits,
matching impedance can actually degrade audio performance.
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more detailed report;
http://www.whatis.com/impedanc.htm
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Impedance measurements - IJL Impedance Bridge - for coarse testing
between 20 and 800 ohms;
http://www.sci.fi/~ijl/zbridge.gif
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shows how impedance in ohms goes down as frequency goes up, at least in
phone lines;
http://www.midcom-inc.com/technology/technotes/tn23p1.html
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what you need for an electronics lab;
http://www.rev.net/~dhcook/pages/equip.htm
High impedance multimeter - either a modern digital or analog FET-input
meter or a multi-purpose VTVM (Vacuum-Tube VoltMeter). A simpler 20,000
ohms-per-volt multitester is usable (and cheap) but a high-impedance
meter provides accurate measurements of low voltages. I don't suggest
autoranging meters - they can be a nuisance in some circumstances. Good
quality digital and analog meters can be found at Radio Shack, Tech
America (you can buy their catalog at Radio Shack) and MCM Electronics
(ask for their free catalog), as well at parts houses, starting at about
$60.00. You can often find good used meters at swap meets and hamfests,
or your Elmer may know someone who has a used meter for sale. A good old
VTVM will do nicely (I have three in the shop) but if you find one at a
swap meet you will probably need to have your Elmer check it out, and
repair and calibrate it for you. I prefer an analog meter - if a signal
is varying a digital meter will drive you nuts where an analog meter
provides a useful indication.
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low impedance bridge causes electrical shocks;
http://www.bassengineering.com/SV_Utility_.htm
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matching impedance for earphones;
http://www.netroglycerine.com/scitoys/scitoys/radio/trouble_shooting.html
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excellent overall page for crystal type receivers!!!!
http://www.netroglycerine.com/scitoys/scitoys/radio/
building a simple crystal radio...excellent!
http://www.netroglycerine.com/scitoys/scitoys/radio/radio.html
The reason a crystal radio does not need any batteries is the amazing
capabilities of the human ear. The ear is extremely sensitive to very
faint sounds. The crystal radio uses only the energy of the radio waves
sent by radio transmitters. These radio transmitters send out enormous
amounts of energy (tens of thousands of watts). However, because they
are usually far away, and we have at most a few hundred feet of wire for
an antenna, the amount of energy we receive with the crystal radio is
measured in billionths of a watt. The human ear can detect sounds that
are less than a millionth of even that.
-- Jerry Wayne Decker / jdecker@keelynet.com http://keelynet.com / "From an Art to a Science" Voice : (214) 324-8741 / FAX : (214) 324-3501 KeelyNet - PO BOX 870716 - Mesquite - Republic of Texas - 75187
