Reg Edwards wrote:

I am writing a program involving an antenna plus two coupled tuned circuits
plus a matched simple receiver.

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker
radio receiver.

Such headphones are more sensitive than modern 8-ohm varieties. I have a
pair of 2000-ohm headphones but unfortunately no means of measuring power or
voltage input.

Just the number of micro-watts please. At what low power input level does
speech or music just BEGIN to fade out to a person of normal hearing? Any
ideas? I could take the average of a few replies.
----
Reg, G4FGQ

EH? WHAT DID HE SAY? :-)

--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

"Richard Clark" wrote in message
...
On Thu, 1 Jul 2004 22:18:27 +0000 (UTC), "Reg Edwards"
wrote:

Rich, why don't you say you don't know. ;o)
---
Reg.

On Thu, 01 Jul 2004 20:43:37 GMT, Richard Clark
wrote:

I don't know

Hi Reggie,

What if I said 43?

Do you actually read responses to your questions? Let's see, there's
enough numbers in it to satisfy lord kelvinator, and enough principle
in it to make sir plushbottom happy, and it even contains the
structure of another unzipped program.

Too demeaning to say thank you, hmmmm?

88's
Richard Clark, KB7QHC

=============================
Thank you for what? ;o)

Anyway, what else do you expect from an Italian clown ?
----
Punchinello, G4FGQ

"Richard Clark" wrote in message
...
On Thu, 1 Jul 2004 22:18:27 +0000 (UTC), "Reg Edwards"
wrote:

Rich, why don't you say you don't know. ;o)
---
Reg.

On Thu, 01 Jul 2004 20:43:37 GMT, Richard Clark
wrote:

I don't know

Hi Reggie,

What if I said 43?

Do you actually read responses to your questions? Let's see, there's
enough numbers in it to satisfy lord kelvinator, and enough principle
in it to make sir plushbottom happy, and it even contains the
structure of another unzipped program.

Too demeaning to say thank you, hmmmm?

88's
Richard Clark, KB7QHC

=============================
Thank you for what? ;o)

Anyway, what else do you expect from an Italian clown ?
----
Punchinello, G4FGQ

On Fri, 2 Jul 2004 14:48:34 +0000 (UTC), "Reg Edwards"
wrote:

Thank you for what? ;o)

Anyway, what else do you expect from an Italian clown ?
Chuckles, however, unless I'm mistaken, you happen to be British,
n'est pas? Or have you regenerated through too much of the vine?

On Fri, 2 Jul 2004 14:48:34 +0000 (UTC), "Reg Edwards"
wrote:

Thank you for what? ;o)

Anyway, what else do you expect from an Italian clown ?
Chuckles, however, unless I'm mistaken, you happen to be British,
n'est pas? Or have you regenerated through too much of the vine?

On Fri, 2 Jul 2004 15:21:22 +0000 (UTC), Harry Whitfield
wrote:

Well, I didn't actually forget - I thought you would know the impedance
of the type F phones. (-:

They appear to be two 2000 ohm earpieces in series, so the impedance is
presumably 4000 ohm.

The DC resistance is 3860 ohm.

I was on the limits of my generator's 50dB attenuation and on the
limits of my voltmeter, so the threshold values are likely to be very
approximate.

We are in the region of 250 pW !

Which is spot on to
a quiet whisper = 6 femtoWatts per cM²

conversation at 1M = 1 nanoWatt per cM²


Hi Harry,

You will have to forgive our Brit, computation is a trial, nailing
down specifics difficult, and hearing is not what it used to be.
None of this is terribly difficult, so I am sure Reggie anticipated
your answer, but simply out of Trollish behavior, he prefers to play
naif (a bit beyond the pale at his age however). This is all, of
course, to escape attribution for his intellectual sources for his
upcoming software :-P

You are welcome Punchinello, even if do you rustle this next release's
code under your apron to hide your plagiarism from view.

73's
Richard Clark, KB7QHC

On Fri, 2 Jul 2004 15:21:22 +0000 (UTC), Harry Whitfield
wrote:

Well, I didn't actually forget - I thought you would know the impedance
of the type F phones. (-:

They appear to be two 2000 ohm earpieces in series, so the impedance is
presumably 4000 ohm.

The DC resistance is 3860 ohm.

I was on the limits of my generator's 50dB attenuation and on the
limits of my voltmeter, so the threshold values are likely to be very
approximate.

We are in the region of 250 pW !

Which is spot on to
a quiet whisper = 6 femtoWatts per cM²

conversation at 1M = 1 nanoWatt per cM²


Hi Harry,

You will have to forgive our Brit, computation is a trial, nailing
down specifics difficult, and hearing is not what it used to be.
None of this is terribly difficult, so I am sure Reggie anticipated
your answer, but simply out of Trollish behavior, he prefers to play
naif (a bit beyond the pale at his age however). This is all, of
course, to escape attribution for his intellectual sources for his
upcoming software :-P

You are welcome Punchinello, even if do you rustle this next release's
code under your apron to hide your plagiarism from view.

73's
Richard Clark, KB7QHC

What if I said 43?

==========================

If you had also mentioned the measurement units, such as femto-Watts, that
would have been the ideal, even perfect, reply to my enquiry and would have
deserved the congratulations of all and sundry.
----
Punchinello, G4FGQ

What if I said 43?

==========================

If you had also mentioned the measurement units, such as femto-Watts, that
would have been the ideal, even perfect, reply to my enquiry and would have
deserved the congratulations of all and sundry.
----
Punchinello, G4FGQ

Reg, G4FGQ wrote:
"I would like to know, crudely, the audio input level to 2000-ohm, non
diaphragm head phones for a nice, comfortable, not too difficult
intensity level."

First problem is sensitivity of the phones. These vary widely.

Satisfactory reception also depends on competing noise in addition to
signal strength. According to the FCC in the U.S.A., you may need 1/2
millivolt for satisfactory reception.

A kilowatt radiated by a medium wave transmitter may produce about 200
millivolts/m at one mile. It depends on antenna and path. Field strength
is proportional to the square root of the watts per square meter times
377.

I used to live about 15 mile4s from a 50 KW station. The signal strength
at a mile from the station could have been 1.5 volts/ m, and at 15 miles
could have been 0.1 V/m. Point is, my crystal set drove a dynamic
loudspeaker directly through the output transformer mounted on the
speaker. It was clearly audible. Impedance presented to the crystal set
was closer to 10,000 ohms at 1 KHz than to 2000 ohms. The speaker and
its cabinet were from a battery vacuum-tube set. The audio power may
have been less than a microwatt, but as a kid my ears were acute.

My 2nd edition GE "Transistor Manual" has 2000-ohm headphone amplifiers
with 2 milliwatts maximum power output.

Chinese stereo headphones claim 20-20KHz response, 32-ohms impedance,
100dB/1mW sensitivity, 140 mW rated input, 400 mW max. etc. Much of this
spec. is target and untrue. Wide variations exist between samples of
these phones claiming similar specs.

The GE book is believable. Class A power output is from the familiar.
First formula says maximum power is 1/2 the product of the peak voltage
and peak current. Load resistance is then the peak voltage divided by
the peak current. So, Load resistance=Epk squared/2Po

When GE prints the circuit of a 2 milliwatt amplifier driving 2000-ohm
phones, I believe it works.

Best regards, Richard Harrison, KB5WZI