"Richard Clark" wrote in message
...
On Tue, 16 Nov 2010 08:42:04 -0600, "amdx" wrote:

Hi Richard.
Near the bottom of this page http://www.crystal-radio.eu/entrafounit1.htm
The author relates this about the use of his 1.62 Mohm input impedance
transformer driving the Adastra 16 ohm driver.

"when I connect a driver unit to the output of the transformer unit, a
1 kHz test tone on the transformer unit input with a amplitude of
1 mV peak-peak can be easily heard."

So, 1 mv peak to peak is .0003535V rms. V^2/R so .3535^2/ 1.62Mohm =7.7 x
10^-14
Or 0.077pw.
Hmm... that is a factor of 1 decimal unit from his earlier claim.
Or did I make the mistake???
Could this measurement have been made with a x10 scope probe and not noted
in recording of the measurement?
That would increase the power to 0.77pw, getting very close to the
minimum
threshold
of hearing.
Inquiring minds want to know.
MikeK

Hi Mike,

As you have allowed, error can wriggle into any part of the
computational chain and slip us a 10dB hit, or a 10dB bonus.

If you have time could you verify the 1 decimal point error that
his own numbers show. It is in the 4th to the last line on this page.
Near the bottom of this page http://www.crystal-radio.eu/entrafounit1.htm
I have contacted him once for clearification of steps on one of his pages.
He has remove his email from some pages and says he can't answer email, he
also
closed his online store.
I don't want to contact him again unless I'm sure that a correction should
be made.

Regarding 10db errors, I have physicist friend that worked for sonics
company,
he found their reference equipment in the water tank had a +10db error.
He reported that to his superior by showing that a transducer he designed
had more
output than the input.
The superior was very happy the design, the superior didn't get the jist of
what my
friend was trying to show him.


I've calibrated laboratory grade Brüel & Kjær microphones and the
process is not done in one sitting.

Here is a very good, online calculator that you should play with:
http://www.ajdesigner.com/phpsound/s...sure_level.php
I asked you for a base power, there is also the matter of distance
from that power source to the ear drum, also the volume of air
involved. By using a combination of these offered equations, you can
(with scrupulous note-taking) find out all the cogent details.

I won't go into the matter of the perception of sound, and the
variation in that with the difference in transverse or longitudinal
sound pressure waves. However, as the word perception is now
introduced; when human senses enter the world of measurement,
measurement becomes vastly more complex (simply because we can fool
ourselves into believing anything). Eliminating the observational
bias is an enormous task.

Perception may have been a bad word to introduce but even if you call it
threshold of hearing you still have the same problems you point out.

Placebo,
Can you say Power Balance Bracelet, homeopathic medicine, magnetic
shoe inserts or the best one Magic Female Relaxant Fragrance also called
"The Relationship Extender" because it can help you to settle differences,
and allow you to happily co-exist with a woman even at the most difficult
of times. :-)


A simple observation flows from that. Take those two speakers,
face-to-face. I mentioned they constructed a tuned hemholz resonator.
Connect your ear tube to that column. The Q of that resonator is
going to take any ambient noise, select out the resonant frequency and
amplify it. Guess what? You get to hear a signal that was never
applied to the leads! Belief can make for a tenacious trap.

Returning to J. Todd's post:
Put an alligator clip on the antenna lead and run it down the tank to
find max volume, then clip it on.
Gives you absolutely EVERYTHING you need. And, frankly, I am
surprised about your source material bemoaning the transformation loss
of using a transformer to connect their speaker to the Tank.

First,
I'll rephrase what I think you meant to say, I am surprised about YOU
bemoaning the source material transformation loss of using a transformer
to connect their speaker to the Tank.
Even I worded that poorly, but are you suggesting I should not work for
1.5db?

Second,
Tapping down on the tank coil may not work as well as first thought.
You still have diode characteristics to overcome, and as you tap down the
voltage
also decreases. I throw this out not fully aware of how lower voltage, lower
impedance affects the diode characterists, but I know the characteristics
will
change with current. I"ll add the contest guru's that I have noted use high
impedance taps to the detector. Although depending on signal strength they
switch in diodes that better match the current the radio signal is
delivering.



Consider that the Tank is, as it suggests, the repository of all the
power available to you (a "gas tank" as it were). That same Tank is
ALSO a universal matching unit. Along the length of the coil (let's
pretend that you can connect alligator clips to any point along the
length of that wire) you have a new Z transform of the entire circuit.
Basically from extreme hi-Z to extreme lo-Z and all Zs in between. The
detector/filter/speaker goes to the point that best matches (pun
intended) its Z (or some dozen or two dozen Ohms) and the antenna goes
to its own value Z (some thousands of Ohms) along the length of the
coil. You already have a transformer, what is the need of a lossy,
second unit?

Still hyave concern about diode characteristics.

Thanks, MikeK


Of course, these connections are going to perturb the Tank and move it
from its rest point. So is any other form of connection. The trick
is to accept this and design that into the final product.

73's
Richard Clark, KB7QHC