Let's do the math and see where that leads us for the specification
offered:
SPL @ 1W/1m: 112.5dB

When driven by .0078 pw we find ourselves 140dB below the 1 Watt that
yields 112.5 dB SPL heard at 1 meter. That translates to -27.5dB re
the absolute lowest level of hearing.

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

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.

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.

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.

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?

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

"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

Here is some more info for you guys to chew on...

http://www.midnightscience.com/downl...es/anatomy.pdf

On Tue, 16 Nov 2010 12:47:02 -0800, Jim wrote:

Here is some more info for you guys to chew on...

http://www.midnightscience.com/downl...es/anatomy.pdf

Thanx Jim,

It seems to be a more complete analysis. I will give it more time
later.

73's
Richard Clark, KB7QHC

On Tue, 16 Nov 2010 12:47:02 -0800, Jim wrote:

Here is some more info for you guys to chew on...

http://www.midnightscience.com/downl...es/anatomy.pdf

OK Jim,

I gave it a look.

I have to wonder from the start, and in the context of Xtal sets that
are usually employed for BCB, where the author decided that a typical
antenna exhibited 50 Ohms resistance and 40pF capacitance.

That was the first of a number of similarly random values assigned to
components that has me drawing up cold. From that, I have to wonder
what the value is in the practice of transforming those values.

73's
Richard Clark, KB7QHC

On 11/18/2010 8:39 AM, Richard Clark wrote:
On Tue, 16 Nov 2010 12:47:02 -0800, wrote:

Here is some more info for you guys to chew on...

http://www.midnightscience.com/downl...es/anatomy.pdf

OK Jim,

I gave it a look.

I have to wonder from the start, and in the context of Xtal sets that
are usually employed for BCB, where the author decided that a typical
antenna exhibited 50 Ohms resistance and 40pF capacitance.

That was the first of a number of similarly random values assigned to
components that has me drawing up cold. From that, I have to wonder
what the value is in the practice of transforming those values.

73's
Richard Clark, KB7QHC

I think that you need to ask the author. I just wanted to add some other
opinions.

I would say that he used some ideal values as a place to start with.
Kind of a 'what if.'

-Jim

On Nov 18, 2:45*pm, Jim wrote:
On 11/18/2010 8:39 AM, Richard Clark wrote:





On Tue, 16 Nov 2010 12:47:02 -0800, *wrote:

Here is some more info for you guys to chew on...

http://www.midnightscience.com/downl...es/anatomy.pdf

OK Jim,

I gave it a look.

I have to wonder from the start, and in the context of Xtal sets that
are usually employed for BCB, where the author decided that a typical
antenna exhibited 50 Ohms resistance and 40pF capacitance.

That was the first of a number of similarly random values assigned to
components that has me drawing up cold. *From that, I have to wonder
what the value is in the practice of transforming those values.

73's
Richard Clark, KB7QHC

I think that you need to ask the author. I just wanted to add some other
opinions.

I would say that he used some ideal values as a place to start with.
Kind of a 'what if.'

* * -Jim- Hide quoted text -

- Show quoted text -

When I was a kid I used to build crystal receivers that had a sliding
tap on the coil titerally wound on a toilet paper tube and adjusting
a variable cap. every station you received had a "best " posotion for
the cap and tap and this also seemed to change from day to day or even
minute to minute. This was my first lesson in the interaction between
impedance and resonance.

Jimmie

On Thu, 18 Nov 2010 10:45:57 -0800, Jim wrote:

I think that you need to ask the author.

Hi Jim,

There are too many indifferent scribblers to merit reading them, much
less entering into a dialog when they already demonstrate a lack of
communication skill. I tried that for years with Art.

Having said that, your suggested link did reveal someone who looked at
the problem carefully and laid out the steps taken to achieve a
result. What was missing was motivation, and a connection to reality
(not being smart-assed, just wondering about the extra components
decorating the schematic is all).

I would say that he used some ideal values as a place to start with.
Kind of a 'what if.'

The "What if" is demonstrated, and it certainly gives scope. However,
ideal circuit values are far from apparent. It is just as easy to use
values any Xtal set owner might find exhibited by his window screen,
as contrasted starting with a full size BCB antenna with an odd
reactive component tossed in for spice (excuse the pun, but it works
at all levels). In other words, it takes absolutely no more effort to
model what one can reasonably expect to find at home, than to go to a
broadcast station and borrow their sky hook (and then antagonize the
Field Engineer by tossing in a haphazard capacitor).

73's
Richard Clark, KB7QHC

On Tue, 16 Nov 2010 14:38:12 -0600, "amdx" wrote:

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.

Why?

Even I worded that poorly, but are you suggesting I should not work for
1.5db?

Why start with a 1.5dB deficit when the Tank is already there to do
the work of matching at no loss?

Second,
Tapping down on the tank coil may not work as well as first thought.

You are going to have to explain that better, because what follows
doesn't.

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.

Changed voltage / changed current = changed Z

That's why the Tank is also called a transformer. You could displace
that function into a secondary, lossy transformer, but the same thing
will happen insofar as your last complaint. In other words, you can
add more loss and get the same grief.

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.

Do they offer a case for fumbling through a selection of diodes? At
first blush, the best is going to be the best - hands down.

Still hyave concern about diode characteristics.

Name one characteristic that presents a concern.

73's
Richard Clark, KB7QHC