Driver to drive?

My first hit for charge of sun...
http://physics.stackexchange.com/questions/73763/what-is-the-electric-charge-of-the-sun-and-its-corona

77 Coulombs.

That's around 1 kV on 80 mF, which given the high temperature of the corona is maybe reasonable except for being shorted out by the local plasma environment. However there's enough complicated magnetic stuff happening in that region that I could imagine charge separation effects going on. Elementary considerations make it seem unlikely that that field remains uncompensated out to infinity, though.

John's original question was whether the solar wind was electrically neutral, which it has to be, very very accurately.

Cheers

Phil Hobbs

 

This is a good example that even a "simple"
Crystal radio is not so simple if you dig
deep enough into the details.
M

 

[George Herold]

On Sunday, April 2, 2017 at 8:41:35 AM UTC-4, pcdh...@gmail.com wrote:

My first hit for charge of sun...
http://physics.stackexchange.com/questions/73763/what-is-the-electric-charge-of-the-sun-and-its-corona

77 Coulombs.

That's around 1 kV on 80 mF, which given the high temperature of the corona is maybe reasonable except for being shorted out by the local plasma environment. However there's enough complicated magnetic stuff happening in that region that I could imagine charge separation effects going on.

Right, 1 kV is not all that much. Lost in the (magnetic) noise
as you say.

George H.

considerations make it seem unlikely that that field remains uncompensated out to infinity, though.

John's original question was whether the solar wind was electrically neutral, which it has to be, very very accurately.

Cheers

Phil Hobbs

 

[Cursitor Doom]

On Sat, 01 Apr 2017 09:32:23 -0500, oldschool wrote:

> Because of the high costs involved,

Right, so it's just another scam to raise taxes - like global moaning. ;-)

 

[Cursitor Doom]

On Sun, 02 Apr 2017 01:56:24 -0400, Michael A. Terrell wrote:

Wouldn't you like to see them dumped into a falling down old cabin,
miles from anywhere with little food, tools, and no money. Most would be
dead inside of a week. Yet the ones they make fun of would have little
or no trouble surviving.

EXACTLY.

 

On Saturday, April 1, 2017 at 11:00:54 PM UTC-4, Clifford Heath wrote:

On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath wrote:

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude.

I'm not a crystal radio guy (RFI on my powerline is so bad that I get *no*
AM stations)(*), but these pages seem to offer a decent overview:

This one-paragraph introduction lays out the big picture:
http://www.bentongue.com/xtalset/1nlxtlsd/1nlxtlsd.html

A short discussion of detector diodes:
http://www.crystal-radio.eu/endiodes.htm

Detailed empirical measurements of diode detectors:
http://www.crystal-radio.eu/endetunittest1.htm

At low signal diodes are square-law detectors, quadrupling output for
every doubling in signal voltage.

The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

These guys' coupling transformers ought to transform (lower) the
effective capacitance of any earphone. And any residual capacitance
is simply compensated by re-tuning, anyhow.

The old crystal earphones were amazing. The crystal radio guys seem
to prefer impedance matching with transformers to magnetic earphones.

(*) Hey, I just scanned the AM band and the years-standing RFI is gone!!
Who knew!

Cheers,
James Arthur

 

[amdx]

On 4/2/2017 3:11 AM, Clifford Heath wrote:

On 02/04/17 15:56, rickman wrote:
On 4/2/2017 12:36 AM, Clifford Heath wrote:
On 02/04/17 13:55, rickman wrote:
On 4/1/2017 10:59 PM, Clifford Heath wrote:
On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath
wrote:
On 29/03/17 02:12, amdx wrote:
On 3/28/2017 2:22 AM, Clifford Heath wrote:
On 28/03/17 13:18, amdx wrote:
On 3/27/2017 6:16 PM, Clifford Heath wrote:
On 27/03/17 23:25, amdx wrote:
On 3/27/2017 6:57 AM, Tauno Voipio wrote:
Joerg, you seem not understand the innermost sense of the
crystal-
radio people. They are closely related to audiophools, and
it is
quite impossible to use sensible technical argumentation here.

I don't get that at all, can you back that up with any facts?

~1MHz, Q=500, bandwidth ~ 2KHz. Remind me why you need Q>1500?

You haven't connected an antenna, and tried to drive a headset
yet.

Umm, I think that was me in about 1971.


More voltage does not create better audio.

But if it is a very weak signal on the antenna, you don't
want to
waste any signal in loss resistances.

You start to *reject* some of the received power as soon as the
Q passes 200ish, and you destroy the audio at the same time.

You can quadruple your received power by doubling your coil
diameter, or fitting a longer wire. That's *far* FAR more
effective than saving 0.2% by using higher Q.

Crystal radios do not use the coil to collect RF energy from the
air,
a long wire antenna of 25ft to 150 is attached tothe coil to pickup
the
RF signal.
If you want to discuss loop antennas, start a new thread.


With a crystal ear-piece, you still may have an impedance matching
problem. For that, you should use an audio transformer *after*
the detector.

Sorry to puncture your dogma.

Take a breath!
I'll start simple, Coil and tuning cap have a unloaded Q of
1000. To extract maximum power you use a load that matches the
Q times Xl of the coil. Loading the coil with it's matched
impedance lowers the Q to 500.

You're making slightly more sense than Rickman, who hasn't
responded to *any* of the numbers I suggested, but one thing
still puzzles me.

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into
more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude. The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

I'm unclear what you are describing. When you say "detune" you are not
describing an effect on the Q, but rather an effect on the tuned
frequency.

Both. When the diode conducts (as it must to transmit power)
it connects the filter capacitance and the capacitance of the
earpiece to the tuned circuit. This will happen whenever the
diode is forward biassed, i.e. when the audio signal is rising.

The extra capacitance on rising audio signals will pull the tuned
circuit to a much lower frequency. As soon as the diode turns off
(when the audio signal starts to fall), the tuned circuit will
jump to a higher frequency, perhaps receiving a different station,
and hence affecting the audio signal once again.

I would expect a double-hump response in the overall receiver,
and the gap between the humps will depend on the filter and
earpiece capacitance.

Maybe you could build one and test that?


If the capacitance of the earpiece impacts the tuning of the
receiver, the adjustment of the tuning capacitor would make up for that
when operated.

Or do you mean detune as a way of describing the reduced Q from the
loading of the circuit by the earpiece? How exactly would the
capacitance of a crystal earpiece affect the loading?

When you measure the capacitance of the earpiece, also measure the
resistance at audio frequencies. The capacitance is only
significant in
that context.

Fair enough. I think I've given some answers above.

I believe a serious crystal set operator will use high end headphones
however. I believe various military headsets are valued for this use
due to their high sensitivity. So the functioning of an inexpensive
peizo earpiece may not be so relevant, but interesting anyway. When I
read about the detail explored to characterize the detecting diode I
was
very impressed. So I can see every part of such a simple radio being
optimized to the nth degree.

Perhaps. The earpiece still has to present some load, or it will
receive no energy. For optimum power transfer, you want its audio
impedance to roughly approximate the equivalent parallel resistance
across the tank - which is why Q gets halved. Or not... perhaps
that only happens on audio half-cycles.

"Presenting a load" is a description of the power transfer. Of course
that has to happen or you don't hear a signal. But how much of that
power gets converted to sound depends on the earpiece used.


Anyhow, those are the reasons for my skepticism about the whole
project. If the detector and earpiece presented a purely resistive
load, or even a fixed capacitive+R load, regardless of audio
polarity, then you wouldn't get a double hump. But I think that's
unlikely.

Theory is nice, but it is easy to miss important aspects. That's why
people build crystal radios, to learn what is important and what is not.

It would need a fairly ornate test setup compared to what I have
available; specifically two different signals, one fixed, one swept,
to see at what frequencies the swept one gets in. Possible, but I
can't easily do it at present.

It seems easier to just ask: with your high-Q receiver, do you ever
hear two stations at the same time that are on different frequencies?
What do the community reporti

The crystal set I built as a kid seemed often to get multiple stations,
but it probably didn't have enough pixie dust.

Clifford Heath

If your going to build a high quality crystal set, then your most
likely going to use high end earphones. Some of the most sensitive
are the, "WWII RCA Big Cans MI-2045E US Navy Deck Talkers Headset'
They are magnetic headphones and as best I can find are fairly low
impedance at 300 ohms. That means you need a transformer to match
you high Q LC to the low impedance headphones.
Ben Tongue did work on that, here;
> http://www.bentongue.com/xtalset/5hpXform/5hpXform.html
Page down past Table 7 and see, "A UTC O-15 'Ouncer' transformer"...
In that section he tests a two transformer arrangement that transforms
a 1.3Meg impedance down to 8 ohms, 300 ohms, 1.2k ohms and 10k ohms.
The transformer loss at 8 ohms is 1.2 db at 1kHz, and I suspect a
little less at 300 ohms.
And then there is the sensitivity of different headphones,

Mouser single old style xtal ear plug - 103

RCA big cans - 128 (before alignment)
Mikek




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This email has been checked for viruses by Avast antivirus software.
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[Cursitor Doom]

On Sun, 02 Apr 2017 20:24:56 +0100, Kevin Aylward wrote:

Its a basic tenant of western law, that you can do anything you like,
unless there is a specific law against it. Like, there does not need to
be a law to allow the drinking of milk. Dah...

No such thing as "western law" Kev.

The alternative is to literally make, millions of laws, like, thou shall
be able to eat apples, thou shall be able to walk at 3 mph....thou
shall...

What? As opposed to millions of laws proscribing AND prescribing various
actions?
We should just go back to the Ten Commandments and put all these law-
makers and lawyers on the dole.

 

On Sat, 01 Apr 2017 09:11:25 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

On Sat, 1 Apr 2017 11:22:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 04/01/2017 11:12 AM, Tom Biasi wrote:
On 4/1/2017 10:32 AM, oldschool@tubes.com wrote:
Scientists have determined that ground is no longer at ground potential.
snip a bunch of junk
Reprinted from: The Electro Scientific Journal

This is what happens from abuse of drugs.
The earth now has an 8 volt potential in reference to what?

I think one of Feynman's lectures asks about what the electrostatic
potential of the Earth is.

The answer is that it's close to zero, since the Earth is immersed in a
conducting medium (the solar wind).

Cheers

Phil Hobbs

Is the solar wind neutral? Spacecraft typically charge a bit negative.
Seems to me that the sun could be a giant thermionic cathode.

The electric field near the ground is big, around 150 volts/meter,
positive going up.

http://www.feynmanlectures.caltech.edu/II_09.html

Now that it is already April 2nd, some serious comments might be
appropriate

Depending on sources, those figures vary quite a lot. While this link
talks about top layer at 50 km (so below ionosphere), in practice, it
appears that the top layer are at about 100 km, i.e in the ionosphere
E-layer.

The current from a single storm cell to the ionosphere is on average
about 1 A, so no wonder that sprites are observed above thunder
clouds, which extends to about 100 km, conforming the top layer
height.

Thus the current from the ground under the storm cell (1 A) to the
ionosphere and then back down as clear air leakage (about 2-10
pA/square meter depending on source) down to the ground will complete
the circuit. Thus, due to ground currents from the surrounding to
under the storm cell will cause some ground potential differences.

This is not much of practical concern compared to solar storms, in
which huge potential differences are created in the ground and quite
huge currents may flow in the ground, with still large potential
differences between sites. If there are a good conductor between two
sites (such as a gas pipeline grounded at both ends). the majority of
this ground current flows through he pipeline, causing electrochemical
problems.

So in reality, any two locations is going to have a different ground
potential and there is no such thing as a universal ground potential.

 

[Kevin Aylward]

"Michael A. Terrell" wrote in message
news:T6mdnSXzgIOeDn3FnZ2dnUU7-IGdnZ2d@earthlink.com...


It's her job tpoo follow the laws, not decide which ones she likes.
In that case, he murdered a police officer in front of a lot of people,
and he has a long history of violence, If she can't or won't do her
job,
she needs to be fired.

What law did she violate?


What laws do you obey?



You didn't answer the question. Which was - What law did she disobey by
refusing to ask for the death penalty?

She is a Florida state attorney and can recommend that the death
sentence to be chosen by the jury. Or not. She simply expressed her
decision to not ask for the death penalty as she had come to the
conclusion, after much study, that it served no useful purpose.

Here is the Florida statute:

- 921.141 Sentence of death or life imprisonment for capital felonies;
further proceedings to determine sentence.—

http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0900-0999/0921/Sections/0921.141.html

Where does it state that she can refuse to seek the death penalty in
every case?

Ho hummm....

I just cant believe that someone is actually using such an inane argument
like this.

Its a basic tenant of western law, that you can do anything you like, unless
there is a specific law against it. Like, there does not need to be a law to
allow the drinking of milk. Dah...
The alternative is to literally make, millions of laws, like, thou shall be
able to eat apples, thou shall be able to walk at 3 mph....thou shall...

Your question is such nonsense, that one can reasonable assume that it is a
troll.

-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

 

On Sunday, April 2, 2017 at 6:48:13 PM UTC-4, Clifford Heath wrote:

On 03/04/17 01:12, dagmargoodboat@yahoo.com wrote:
On Saturday, April 1, 2017 at 11:00:54 PM UTC-4, Clifford Heath wrote:
On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath wrote:

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude.

I'm not a crystal radio guy (RFI on my powerline is so bad that I get *no*
AM stations)(*), but these pages seem to offer a decent overview:

This one-paragraph introduction lays out the big picture:
http://www.bentongue.com/xtalset/1nlxtlsd/1nlxtlsd.html

A short discussion of detector diodes:
http://www.crystal-radio.eu/endiodes.htm

Detailed empirical measurements of diode detectors:
http://www.crystal-radio.eu/endetunittest1.htm

Interesting articles - I just read all three - but none of them
mention the effect I'm suggesting, and none of the experimental
setups would see it. Ben Tongue gets close in his paragraph
"Tuned circuit loss and bandwidth considerations", but doesn't
acknowledge the assymetric load characteristic.

I bet I could construct an LTSpice simulation that would show
it clearly.

Agreed, you could simulate it, and it isn't addressed in the articles
I read, but does it do much other than add a bit of harmonic distortion?
I don't see how.

At low signal diodes are square-law detectors, quadrupling output for
every doubling in signal voltage.

The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

These guys' coupling transformers ought to transform (lower) the
effective capacitance of any earphone. And any residual capacitance
is simply compensated by re-tuning, anyhow.

Yes, but that capacitance is only coupled to the antenna during
half-cycles of the audio, while the diode is conducting. So you
have two frequencies being tuned. While the diode is off, the
alternate frequency is the one which will turn it back on again
and slew the tuned frequency to the one you hear.

That would explain a lot of what I recall hearing in my crystal
earpiece, anyhow; effectively audio intermodulation from adjacent
stations.

That's always a danger in a crowded band, yes.

I guess that's why the Benny is useful; not for the reason he
describes, but to make the load appear more resistive.

Interesting stuff.

(*) Hey, I just scanned the AM band and the years-standing RFI is gone!!

Perhaps you replaced a bit of equipment that had a crappy wall wart?
Or a neighbour did!

Not me, it was far too powerful, and stronger outside than inside. I
suspect an aging line and pole replacement program in progress likely
removed a HV leaker, somewhere in the neighborhood.

RFI was so bad I hadn't bothered checking the AM band in perhaps a year or
two--it had been like listening to a Tesla coil or an EDM machine.

> Clifford Heath.

Cheers,
James Arthur

 

[Clifford Heath]

On 02/04/17 22:35, amdx wrote:

On 4/2/2017 3:11 AM, Clifford Heath wrote:
On 02/04/17 15:56, rickman wrote:
On 4/2/2017 12:36 AM, Clifford Heath wrote:
On 02/04/17 13:55, rickman wrote:
On 4/1/2017 10:59 PM, Clifford Heath wrote:
On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath
wrote:
On 29/03/17 02:12, amdx wrote:
On 3/28/2017 2:22 AM, Clifford Heath wrote:
On 28/03/17 13:18, amdx wrote:
On 3/27/2017 6:16 PM, Clifford Heath wrote:
On 27/03/17 23:25, amdx wrote:
On 3/27/2017 6:57 AM, Tauno Voipio wrote:
Joerg, you seem not understand the innermost sense of the
crystal-
radio people. They are closely related to audiophools, and
it is
quite impossible to use sensible technical argumentation
here.

I don't get that at all, can you back that up with any
facts?

~1MHz, Q=500, bandwidth ~ 2KHz. Remind me why you need Q>1500?

You haven't connected an antenna, and tried to drive a headset
yet.

Umm, I think that was me in about 1971.


More voltage does not create better audio.

But if it is a very weak signal on the antenna, you don't
want to
waste any signal in loss resistances.

You start to *reject* some of the received power as soon as the
Q passes 200ish, and you destroy the audio at the same time.

You can quadruple your received power by doubling your coil
diameter, or fitting a longer wire. That's *far* FAR more
effective than saving 0.2% by using higher Q.

Crystal radios do not use the coil to collect RF energy from the
air,
a long wire antenna of 25ft to 150 is attached tothe coil to
pickup
the
RF signal.
If you want to discuss loop antennas, start a new thread.


With a crystal ear-piece, you still may have an impedance
matching
problem. For that, you should use an audio transformer *after*
the detector.

Sorry to puncture your dogma.

Take a breath!
I'll start simple, Coil and tuning cap have a unloaded Q of
1000. To extract maximum power you use a load that matches the
Q times Xl of the coil. Loading the coil with it's matched
impedance lowers the Q to 500.

You're making slightly more sense than Rickman, who hasn't
responded to *any* of the numbers I suggested, but one thing
still puzzles me.

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into
more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude. The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

I'm unclear what you are describing. When you say "detune" you are
not
describing an effect on the Q, but rather an effect on the tuned
frequency.

Both. When the diode conducts (as it must to transmit power)
it connects the filter capacitance and the capacitance of the
earpiece to the tuned circuit. This will happen whenever the
diode is forward biassed, i.e. when the audio signal is rising.

The extra capacitance on rising audio signals will pull the tuned
circuit to a much lower frequency. As soon as the diode turns off
(when the audio signal starts to fall), the tuned circuit will
jump to a higher frequency, perhaps receiving a different station,
and hence affecting the audio signal once again.

I would expect a double-hump response in the overall receiver,
and the gap between the humps will depend on the filter and
earpiece capacitance.

Maybe you could build one and test that?


If the capacitance of the earpiece impacts the tuning of the
receiver, the adjustment of the tuning capacitor would make up for
that
when operated.

Or do you mean detune as a way of describing the reduced Q from the
loading of the circuit by the earpiece? How exactly would the
capacitance of a crystal earpiece affect the loading?

When you measure the capacitance of the earpiece, also measure the
resistance at audio frequencies. The capacitance is only
significant in
that context.

Fair enough. I think I've given some answers above.

I believe a serious crystal set operator will use high end headphones
however. I believe various military headsets are valued for this use
due to their high sensitivity. So the functioning of an inexpensive
peizo earpiece may not be so relevant, but interesting anyway. When I
read about the detail explored to characterize the detecting diode I
was
very impressed. So I can see every part of such a simple radio being
optimized to the nth degree.

Perhaps. The earpiece still has to present some load, or it will
receive no energy. For optimum power transfer, you want its audio
impedance to roughly approximate the equivalent parallel resistance
across the tank - which is why Q gets halved. Or not... perhaps
that only happens on audio half-cycles.

"Presenting a load" is a description of the power transfer. Of course
that has to happen or you don't hear a signal. But how much of that
power gets converted to sound depends on the earpiece used.


Anyhow, those are the reasons for my skepticism about the whole
project. If the detector and earpiece presented a purely resistive
load, or even a fixed capacitive+R load, regardless of audio
polarity, then you wouldn't get a double hump. But I think that's
unlikely.

Theory is nice, but it is easy to miss important aspects. That's why
people build crystal radios, to learn what is important and what is not.

It would need a fairly ornate test setup compared to what I have
available; specifically two different signals, one fixed, one swept,
to see at what frequencies the swept one gets in. Possible, but I
can't easily do it at present.

It seems easier to just ask: with your high-Q receiver, do you ever
hear two stations at the same time that are on different frequencies?
What do the community reporti

The crystal set I built as a kid seemed often to get multiple stations,
but it probably didn't have enough pixie dust.

If your going to build a high quality crystal set, then your most
likely going to use high end earphones. Some of the most sensitive
are the, "WWII RCA Big Cans MI-2045E US Navy Deck Talkers Headset'
They are magnetic headphones and as best I can find are fairly low
impedance at 300 ohms. That means you need a transformer to match
you high Q LC to the low impedance headphones.

That's good to know, but not relevant to the dual impedance
caused by the detector's polarization.

I mentioned the peaky resonances in crystal earpieces, but
they're not the main problem.

Ben Tongue did work on that, here;
http://www.bentongue.com/xtalset/5hpXform/5hpXform.html
Page down past Table 7 and see, "A UTC O-15 'Ouncer' transformer"...
In that section he tests a two transformer arrangement that transforms
a 1.3Meg impedance down to 8 ohms, 300 ohms, 1.2k ohms and 10k ohms.
The transformer loss at 8 ohms is 1.2 db at 1kHz, and I suspect a
little less at 300 ohms.
And then there is the sensitivity of different headphones,

Mouser single old style xtal ear plug - 103

RCA big cans - 128 (before alignment)
Mikek




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[John Larkin]

On Sun, 02 Apr 2017 22:24:39 +0300, upsidedown@downunder.com wrote:

On Sat, 01 Apr 2017 09:11:25 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sat, 1 Apr 2017 11:22:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 04/01/2017 11:12 AM, Tom Biasi wrote:
On 4/1/2017 10:32 AM, oldschool@tubes.com wrote:
Scientists have determined that ground is no longer at ground potential.
snip a bunch of junk
Reprinted from: The Electro Scientific Journal

This is what happens from abuse of drugs.
The earth now has an 8 volt potential in reference to what?

I think one of Feynman's lectures asks about what the electrostatic
potential of the Earth is.

The answer is that it's close to zero, since the Earth is immersed in a
conducting medium (the solar wind).

Cheers

Phil Hobbs

Is the solar wind neutral? Spacecraft typically charge a bit negative.
Seems to me that the sun could be a giant thermionic cathode.

The electric field near the ground is big, around 150 volts/meter,
positive going up.

http://www.feynmanlectures.caltech.edu/II_09.html

Now that it is already April 2nd, some serious comments might be
appropriate

Depending on sources, those figures vary quite a lot. While this link
talks about top layer at 50 km (so below ionosphere), in practice, it
appears that the top layer are at about 100 km, i.e in the ionosphere
E-layer.

The current from a single storm cell to the ionosphere is on average
about 1 A, so no wonder that sprites are observed above thunder
clouds, which extends to about 100 km, conforming the top layer
height.

Thus the current from the ground under the storm cell (1 A) to the
ionosphere and then back down as clear air leakage (about 2-10
pA/square meter depending on source) down to the ground will complete
the circuit. Thus, due to ground currents from the surrounding to
under the storm cell will cause some ground potential differences.

This is not much of practical concern compared to solar storms, in
which huge potential differences are created in the ground and quite
huge currents may flow in the ground, with still large potential
differences between sites. If there are a good conductor between two
sites (such as a gas pipeline grounded at both ends). the majority of
this ground current flows through he pipeline, causing electrochemical
problems.

So in reality, any two locations is going to have a different ground
potential and there is no such thing as a universal ground potential.

You can stick a pair of rods into the ground some distance apart, and
measure/listen to the voltage gradient.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Clifford Heath]

On 03/04/17 01:12, dagmargoodboat@yahoo.com wrote:

On Saturday, April 1, 2017 at 11:00:54 PM UTC-4, Clifford Heath wrote:
On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath wrote:

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude.

I'm not a crystal radio guy (RFI on my powerline is so bad that I get *no*
AM stations)(*), but these pages seem to offer a decent overview:

This one-paragraph introduction lays out the big picture:
http://www.bentongue.com/xtalset/1nlxtlsd/1nlxtlsd.html

A short discussion of detector diodes:
http://www.crystal-radio.eu/endiodes.htm

Detailed empirical measurements of diode detectors:
http://www.crystal-radio.eu/endetunittest1.htm

Interesting articles - I just read all three - but none of them
mention the effect I'm suggesting, and none of the experimental
setups would see it. Ben Tongue gets close in his paragraph
"Tuned circuit loss and bandwidth considerations", but doesn't
acknowledge the assymetric load characteristic.

I bet I could construct an LTSpice simulation that would show
it clearly.

At low signal diodes are square-law detectors, quadrupling output for
every doubling in signal voltage.

The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

These guys' coupling transformers ought to transform (lower) the
effective capacitance of any earphone. And any residual capacitance
is simply compensated by re-tuning, anyhow.

Yes, but that capacitance is only coupled to the antenna during
half-cycles of the audio, while the diode is conducting. So you
have two frequencies being tuned. While the diode is off, the
alternate frequency is the one which will turn it back on again
and slew the tuned frequency to the one you hear.

That would explain a lot of what I recall hearing in my crystal
earpiece, anyhow; effectively audio intermodulation from adjacent
stations.

I guess that's why the Benny is useful; not for the reason he
describes, but to make the load appear more resistive.

Interesting stuff.

> (*) Hey, I just scanned the AM band and the years-standing RFI is gone!!

Perhaps you replaced a bit of equipment that had a crappy wall wart?
Or a neighbour did!

Clifford Heath.

 

[amdx]

On 4/2/2017 8:39 PM, dagmargoodboat@yahoo.com wrote:

On Sunday, April 2, 2017 at 6:48:13 PM UTC-4, Clifford Heath wrote:
On 03/04/17 01:12, dagmargoodboat@yahoo.com wrote:
On Saturday, April 1, 2017 at 11:00:54 PM UTC-4, Clifford Heath wrote:
On 31/03/17 15:40, dagmargoodboat@yahoo.com wrote:
On Wednesday, March 29, 2017 at 6:59:53 PM UTC-4, Clifford Heath wrote:

Why worry about increasing Q above 500, when you can get more
than the extra 0.2% (lost energy at Q=500) by adding 3 inches
more antenna wire?

Possible answer:

Because, if you actually need Q=500 for selectivity, an LC tank
with an unloaded Q of 500 leaves you no power to drive an earphone?
And any improvement in unloaded tank 'Q' translates directly into more
power available for audio output?

James, thanks.

That's the sanest answer yet and goes some way to explaining
what the xtal guys are after.

However, the single-diode detector is a very assymetric load.
That's going to affect things a bit, don't you think? By which
I mean that the coil will "see" the load during rising amplitude,
but not during falling amplitude.

I'm not a crystal radio guy (RFI on my powerline is so bad that I get *no*
AM stations)(*), but these pages seem to offer a decent overview:

This one-paragraph introduction lays out the big picture:
http://www.bentongue.com/xtalset/1nlxtlsd/1nlxtlsd.html

A short discussion of detector diodes:
http://www.crystal-radio.eu/endiodes.htm

Detailed empirical measurements of diode detectors:
http://www.crystal-radio.eu/endetunittest1.htm

Interesting articles - I just read all three - but none of them
mention the effect I'm suggesting, and none of the experimental
setups would see it. Ben Tongue gets close in his paragraph
"Tuned circuit loss and bandwidth considerations", but doesn't
acknowledge the assymetric load characteristic.

I bet I could construct an LTSpice simulation that would show
it clearly.

Agreed, you could simulate it, and it isn't addressed in the articles
I read, but does it do much other than add a bit of harmonic distortion?
I don't see how.

At low signal diodes are square-law detectors, quadrupling output for
every doubling in signal voltage.

The coupling to a crystal
earpiece (generally capacitive, but highly reactive load) is
gonna make quite things weird, by pulling the resonant frequency
around a lot, dependent on the audio signal...

I should pull out my old xtal earpieces and measure the capacitance.
I suspect they'd detune a high-Q front end quite a bit, and that
really calls into question the use of Q to limit bandwidth.

These guys' coupling transformers ought to transform (lower) the
effective capacitance of any earphone. And any residual capacitance
is simply compensated by re-tuning, anyhow.

Yes, but that capacitance is only coupled to the antenna during
half-cycles of the audio, while the diode is conducting. So you
have two frequencies being tuned. While the diode is off, the
alternate frequency is the one which will turn it back on again
and slew the tuned frequency to the one you hear.

That would explain a lot of what I recall hearing in my crystal
earpiece, anyhow; effectively audio intermodulation from adjacent
stations.

That's always a danger in a crowded band, yes.

I guess that's why the Benny is useful; not for the reason he
describes, but to make the load appear more resistive.

Interesting stuff.

(*) Hey, I just scanned the AM band and the years-standing RFI is gone!!

Perhaps you replaced a bit of equipment that had a crappy wall wart?
Or a neighbour did!

Not me, it was far too powerful, and stronger outside than inside. I
suspect an aging line and pole replacement program in progress likely
removed a HV leaker, somewhere in the neighborhood.

RFI was so bad I hadn't bothered checking the AM band in perhaps a year or
two--it had been like listening to a Tesla coil or an EDM machine.

Clifford Heath.

Cheers,
James Arthur

A place I worked at had a hash in the AM band, I walked around with my
am radio and traced it to a power pole about 35ft from our building.
We called the power company and told them they had an arcing power pole
at the corner of...
They responded immediately and by the end of the day our noise was
gone. Looking back saying the pole was arcing was maybe just a little
over kill, but it sure got action.
Mikek

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

On Sunday, April 2, 2017 at 10:22:37 PM UTC-4, amdx wrote:

On 4/2/2017 8:39 PM, dagmargoodboat@yahoo.com wrote:
On Sunday, April 2, 2017 at 6:48:13 PM UTC-4, Clifford Heath wrote:
On 03/04/17 01:12, dagmargoodboat@yahoo.com wrote:

(*) Hey, I just scanned the AM band and the years-standing RFI is gone!!

Perhaps you replaced a bit of equipment that had a crappy wall wart?
Or a neighbour did!

Not me, it was far too powerful, and stronger outside than inside. I
suspect an aging line and pole replacement program in progress likely
removed a HV leaker, somewhere in the neighborhood.

RFI was so bad I hadn't bothered checking the AM band in perhaps a year or
two--it had been like listening to a Tesla coil or an EDM machine.


A place I worked at had a hash in the AM band, I walked around with my
am radio and traced it to a power pole about 35ft from our building.

I walked around outside a bit with an AM radio when we were having the RFI,
but it was everywhere--I couldn't get a bearing on it, other than it was
on the powerlines.

We called the power company and told them they had an arcing power pole
at the corner of...

I probably should've done that. We have some hams in the area;
I'm surprised none of them complained. Until yesterday I'd assumed
it was one of my neighbors arc-welding 24/7, or trying to reanimate
Frankenstein perhaps.

They responded immediately and by the end of the day our noise was
gone. Looking back saying the pole was arcing was maybe just a little
over kill, but it sure got action.

Nice work, Sherlock!

Cheers,
James Arthur

 

On Wednesday, April 5, 2017 at 11:42:06 AM UTC+10, Michael Terrell wrote:

bill.sloman@ieee.org wrote:
On Sunday, April 2, 2017 at 4:07:07 PM UTC+10, Michael Terrell wrote:
rickman wrote:
On 3/26/2017 2:11 AM, Michael A. Terrell wrote:
Kevin Aylward wrote:
wrote in message news:s1tcdctmds0hl22fo9hpbh5enshegc86gm@4ax.com...

On Sat, 25 Mar 2017 03:32:41 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Kevin Aylward wrote:
wrote in message news:mnq8dcpnbekopn07j0cu3crq12hq0905l1@4ax.com....

On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

snip

Like, what specific law says that anybody has to demand the death of
someone else? Dah....

It's her job to follow the laws, not decide which ones she likes.
In that case, he murdered a police officer in front of a lot of people,

Please cite the exact law that says that a prosecutor must demand the
death penalty.

Sure, a prosecutor may well be obliged to do what is in the best
interest of society, in which case the evidence appears to show that the
"best" course of action, is to not seek the death penalty.

http://www.amnestyusa.org/our-work/issues/death-penalty/us-death-penalty-facts/death-penalty-cost

Please show the exact law that allows employees to refuse to do their
jobs, yet keep their jobs.

Show me the law that makes it a crime!!!

Show one that states otherwise.

You can't prove a negative. If you don't do your job to the satisfaction of your employer, that can constitute grounds for dismissal. Doing it badly enough can constitute negligence, and you can get sued for the consequences.

Neither is criminal. There is a crime of criminal negligence

https://en.wikipedia.org/wiki/Criminal_negligence

but a prosecutor failing to ask for the death penalty isn't going to qualify. Asking for the death penalty in a situation where this made the jury less likely to convict might qualify, but no prosecutor is going to get charged with that - simply because it would be too hard to get a conviction.

As usual, you don't know shit. The Governor just took every similar
case from this ass and assigned them to another AG.

That's politics, not law, but you don't know enough to realise that there's a difference.

Some other politicians are trying to have her removed from office, since she
refuses to do her job. But then, what do you know about work ethics?

I know quite a lot about work ethics, and more than enough to know that what politicians want has everything to do with what they are trying to sell to the voters, and nothing to do with legal responsibilities.

The death penalty does sell well to idiot rednecks like you, who refuse to realise that the law is a little more complicated than you can imagine.

This is the third email address you've used lately to troll your
dumbassery, but I have an infinite supply of 'Troll-Be-Gone'.

I don't peddle dum-assed ideas - that's your job. You are too much of dumb-ass to recognise the inadequacies of your own perceptions, and comfort yourself with the idea that if you don't agree with something it has to be dumb-assed, when in reality it's quite the other way around.

And I haven't changed my posting identity. I have several that I could use to post here, but I go to some trouble to use only the ieee.org address, which is the one you have responded to here.

I couldn't care less whether you read my posts - your responses are down there with krw's in being utterly worthless - and I'm not going to go to any trouble at all to evade your kill-filing mechanisms (which you don't seem to understand any better than Cursitor Doom understands his).

--
Bill Sloman, Sydney

 

[Michael A. Terrell]

bill.sloman@ieee.org wrote:

On Sunday, April 2, 2017 at 4:07:07 PM UTC+10, Michael Terrell wrote:
rickman wrote:
On 3/26/2017 2:11 AM, Michael A. Terrell wrote:
Kevin Aylward wrote:
wrote in message news:s1tcdctmds0hl22fo9hpbh5enshegc86gm@4ax.com...

On Sat, 25 Mar 2017 03:32:41 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Kevin Aylward wrote:
wrote in message news:mnq8dcpnbekopn07j0cu3crq12hq0905l1@4ax.com...

On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

snip

Like, what specific law says that anybody has to demand the death of
someone else? Dah....

It's her job to follow the laws, not decide which ones she likes.
In that case, he murdered a police officer in front of a lot of people,

Please cite the exact law that says that a prosecutor must demand the
death penalty.

Sure, a prosecutor may well be obliged to do what is in the best
interest of society, in which case the evidence appears to show that the
"best" course of action, is to not seek the death penalty.

http://www.amnestyusa.org/our-work/issues/death-penalty/us-death-penalty-facts/death-penalty-cost

Please show the exact law that allows employees to refuse to do their
jobs, yet keep their jobs.

Show me the law that makes it a crime!!!

Show one that states otherwise.

You can't prove a negative. If you don't do your job to the satisfaction of your employer, that can constitute grounds for dismissal. Doing it badly enough can constitute negligence, and you can get sued for the consequences.

Neither is criminal. There is a crime of criminal negligence

https://en.wikipedia.org/wiki/Criminal_negligence

but a prosecutor failing to ask for the death penalty isn't going to qualify. Asking for the death penalty in a situation where this made the jury less likely to convict might qualify, but no prosecutor is going to get charged with that - simply because it would be too hard to get a conviction.

As usual, you don't know shit. The Governor just took every similar
case from this ass and assigned them to another AG. Some other
politicians are trying to have her removed from office, since she
refuses to do her job. But then, what do you know about work ethics?


This is the third email address you've used lately to troll your
dumbassery, but I have an infinite supply of 'Troll-Be-Gone'.

--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Bill Wright]

On 08/04/2017 12:37, pamela wrote:

However his OFF-ON is so quick that it makes me think on some
occassions he could create a power surge.

I would have thought he'd cause problems not fix them. Very brief power
failures seem to cause a lot of glitches.

Bill

 

[Bill Wright]

On 08/04/2017 17:15, MJC wrote:

> My Humax (old 9200T) will record even when in standby.

They all will

Bill