Driver to drive?

rickman · Mar 29, 2017

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

--

Rick C

amdx · Mar 30, 2017

On 3/29/2017 12:47 PM, rickman wrote:

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

Probably Ben Tongue's site, he has multiple writings about diodes,
The diode you pick is very dependent on the signal strength.
> http://www.bentongue.com/xtalset/xtalset.html

Mikek

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Phil Allison · Mar 30, 2017

Mike Perkins wrote:

Phil Allison wrote:
mako...@yahoo.com wrote:

And in the AM broadcast band, the SNR is usually not determined by the
radio but rather by the atmospheric noise and interference form
other stations,,,,

** Providing there is an adequate signal from the antenna carrying the wanted broadcast.

so even though you may build an antenna that puts out more "volts"
it will not be helpful for picking up weaker signals.

** Complete non-sequitur and obviously false.

Are you suggesting the converse is true? Where external noise sources
and interference are substantially above the thermally generated noise
floor and first amplifier noise, the SNR will magically improve if you
use a bigger aerial?

** In another post on the same date, I pointed out the obvious truism that there is no such limit to the s/n of an AM broadcast.

In the primary reception area of an transmitter, the SIGNAL can be hugely bigger than the ambient and natural noise.

Only when DXing is the signal seriously compromised by noise. Even then, a directional antenna will favour the broadcast over noise arriving from all directions.

FYI:

the opposite of a false statement is not usually a true statement.

...... Phil

..... Phil

Mar 30, 2017

On Wed, 29 Mar 2017 13:28:05 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 10:23 AM, Joerg wrote:
On 2017-03-28 02:51, upsidedown@downunder.com wrote:
On Mon, 27 Mar 2017 23:47:00 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/27/2017 12:22 PM, Joerg wrote:
On 2017-03-27 07:59, rickman wrote:
On 3/27/2017 10:46 AM, Joerg wrote:

The Q is over 500. It was claimed in this thread that PVC is not
suitable as coil winding material and this proves that it is quite
suitable. Which I already knew because I've used it in RF power amps
decades ago.

Again, context. You are living in a different world. PVC is *not*
suitable in the crystal radio world because there are *much* better
materials. If PVC was the only material available it would be a
*great*
coil support. If mud was the only material available it would be a
*great* coil support.

Can you explain why one even want a Q in excess of 500 in the AM band?

That is the _unloaded_ Qu. Still 500 sounds excessive high for
ordinary LC circuits or loop antennas. At higher frequencies a silver
coated cavity resonator would easily ac hive that.

Q is a measure of the losses. Having a high Q in the coil means the
coil has lower losses. Having a higher Q in the tuning capacitor means
it has lower losses. The lower the losses the more power that ends up
in the headphones.

When you connect the load you get the _loaded_ Ql. This Ql determines
the actual receiver bandwidth. For AM reception a 10 kHz bandwidth
would be desirable, so at 1 MHz the loaded Ql=100 would be suitable.

Exactly, not 500 or 1000. Still, even with a somewhat matching loaded Q
the audio quality is mediocre because a simple tuned circuit has a poor
shape factor. This results in higher audio frequencies being muffled,
speech to be less easy to understand and as you said further below a
strong station on the next AM channel will spoil the whole experience by
swamping the signal.

The Qu/Ql ratio determines the signal losses. a Qu/Ql=10:1 gives less
than 1 dB losses, a 2:1 ratio and the loss is a few decibels. A
500/100 ratio gives about 2 dB losses.

Which is close to impossible to even hear.

... In receivers with
amplification, this loss is directly added to the noise figure. For
this reason, it is undesirable to have too high loaded Ql in front of
the first amplifier stage. On the other hand, a wide front end can
easily overload the first amplifier or mixer. A high Ql filter between
the first amplifier and mixer helps a lot. This is an issue on VHF and
above.

The Q of the radio won't be the same as the Q of the components because
you are sucking off power to drive the headphones. Besides, the number
you came up with (10 kHz) would be perfect for AM radio if you can get
that, that is the channel spacing. Great selectivity.
It should be noted that BW = f / Q only gives the -3 dB point of the
response curve. There might be a 40-60 dB signal on the adjacent
channel, which will effectively kill the reception of the wanted
signal.

There is probably some sort of sports ambition where the guy with the
highest Q wins a trophy or at least a free beer

It *is* a hobby. No one builds a crystal radio set because he wants to
listen to talk radio.

This seems to be a US specific thing. In Europe, there are not much
local MF broadcasts any more. The situation was different 50 years
ago, but now it is hard to find a local LF/MF/HF transmitter within
1000 km, thus a simple crystal radio is more or less useless.

>You comments indicate you neither understand the hobby

That is US country specific.

nor do you really
understand the technology, but I believe the latter is a choice on your
part. You seem to be deliberately refusing to try to understand what is
being said.

Why should I deliberately bang my head against the wall ?

Your comment above about not being able to hear a few dB is a good
example of your mindset.

1-2 dB of extra loss is significant in UHF EME (moonbounce)
communication, in which the amplifier itself has a noise figure in the
order of 1 dB (i.e. 100 K noise temperature). For any MF communication
circuits, the band noise is huge from location to location, from day
to day or from hour to hour, so a 1-2 dB variation doesn't really
cause problems.

Rather than trying to understand why anyone
would care if tweaking the core material for a coil adds a few dB, you
make a comment showing your disdain. Open your mind. Look at the
bigger picture. You tell me why anyone cares about the few dB from
optimizing this one feature?

I really do not understand why you make such fuss about LF, MF and
lower HF. However, those few decibels are of great concern in UHF/SHF
bands.

Mar 30, 2017

On Wed, 29 Mar 2017 13:47:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

Why do you want to keep the receiver completely passive ?

A small solar cell o the headphone will charge a small battery, that
can be used to drive a small RF/IF/AF amplifier over the night.

How about a two circuit MF AM receiver, with one resonant circuit
tuned to your local strong MF (AM) station and the rectified DC power
is used to run the "DX" receiver ?

Ralph Barone · Mar 30, 2017

Jeff Liebermann <jeffl@cruzio.com> wrote:

On Wed, 29 Mar 2017 10:18:33 +1100, Clifford Heath
no.spam@please.net> 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?

Because the added 3 inches will add equal amounts of signal and noise,
resulting in no net improvement.

Well, maybe not in the case of a crystal radio. The "noise" portion of the
SNR in a crystal radio also practically includes ambient audio noise and
the noise between your ears (for those of you with tinnitus). Cranking up
the RF signal and the RF noise in equal proportions can still help.

amdx · Mar 30, 2017

On 3/28/2017 6:18 PM, 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?

I don't know the math but logically I don't see that adding 3 inches
to a 50ft antenna is going to have the same effect as doubling Q.
Here's a video, this guy built a very nice set, it's worth watching.
> https://www.youtube.com/watch?v=Bw4IiTR3Tqw

Mikek

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amdx · Mar 30, 2017

On 3/29/2017 4:47 PM, upsidedown@downunder.com wrote:

On Wed, 29 Mar 2017 13:47:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

Why do you want to keep the receiver completely passive ?

A small solar cell o the headphone will charge a small battery, that
can be used to drive a small RF/IF/AF amplifier over the night.

How about a two circuit MF AM receiver, with one resonant circuit
tuned to your local strong MF (AM) station and the rectified DC power
is used to run the "DX" receiver ?

People have built them as you have suggested.

Mikek

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Mike Perkins · Mar 30, 2017

On 16/03/2017 00:22, Phil Allison wrote:

mako...@yahoo.com wrote:

And in the AM broadcast band, the SNR is usually not determined by the
radio but rather by the atmospheric noise and interference form
other stations,,,,

** Providing there is an adequate signal from the antenna carrying the wanted broadcast.

so even though you may build an antenna that puts out more "volts"
it will not be helpful for picking up weaker signals.

** Complete non-sequitur and obviously false.

Are you suggesting the converse is true? Where external noise sources
and interference are substantially above the thermally generated noise
floor and first amplifier noise, the SNR will magically improve if you
use a bigger aerial?

--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

Jeff Liebermann · Mar 30, 2017

On Wed, 29 Mar 2017 10:18:33 +1100, Clifford Heath
<no.spam@please.net> 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?

Because the added 3 inches will add equal amounts of signal and noise,
resulting in no net improvement. It's always fun to drag things to
their logical extreme. Instead of 3 inches, add 3 miles of wire. The
recovered energy will be huge and possibly sufficient to draw an arc.
But, so will the received atmospheric noise be huge by the same
amount. Besides less loss, a higher Q also means more selectivity, so
the receiver won't act the like the first crystal set I built in
middle skool, which received and demodulated most of the AM broadcast
band simultaneously. There's an upper limit to Q as set by the
modulation bandwidth. The AM broadcast band runs about 10KHz per
channel, so the maximum usable loaded Q would be:
Q = 1,000 KHz / 10 KHz = 100
Any Q more than 100 at BCB frequencies will begin dropping the higher
audio frequencies from the modulation. Too narrow band, and all you
can hear will be CW (Morse Code). There's also the problem of tuning
stability, where anything that causes the high Q coil to drift in
frequency, will produce even harmonic distortion of the audio. Copper
wire is not particularly temperature stable and will require some form
of frequency or tuning stabilization.

Ok, back to taxes...

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

rickman · Mar 30, 2017

On 3/29/2017 5:37 PM, upsidedown@downunder.com wrote:

On Wed, 29 Mar 2017 13:28:05 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 10:23 AM, Joerg wrote:
On 2017-03-28 02:51, upsidedown@downunder.com wrote:
On Mon, 27 Mar 2017 23:47:00 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/27/2017 12:22 PM, Joerg wrote:
On 2017-03-27 07:59, rickman wrote:
On 3/27/2017 10:46 AM, Joerg wrote:

The Q is over 500. It was claimed in this thread that PVC is not
suitable as coil winding material and this proves that it is quite
suitable. Which I already knew because I've used it in RF power amps
decades ago.

Again, context. You are living in a different world. PVC is *not*
suitable in the crystal radio world because there are *much* better
materials. If PVC was the only material available it would be a
*great*
coil support. If mud was the only material available it would be a
*great* coil support.

Can you explain why one even want a Q in excess of 500 in the AM band?

That is the _unloaded_ Qu. Still 500 sounds excessive high for
ordinary LC circuits or loop antennas. At higher frequencies a silver
coated cavity resonator would easily ac hive that.

Q is a measure of the losses. Having a high Q in the coil means the
coil has lower losses. Having a higher Q in the tuning capacitor means
it has lower losses. The lower the losses the more power that ends up
in the headphones.

When you connect the load you get the _loaded_ Ql. This Ql determines
the actual receiver bandwidth. For AM reception a 10 kHz bandwidth
would be desirable, so at 1 MHz the loaded Ql=100 would be suitable.

Exactly, not 500 or 1000. Still, even with a somewhat matching loaded Q
the audio quality is mediocre because a simple tuned circuit has a poor
shape factor. This results in higher audio frequencies being muffled,
speech to be less easy to understand and as you said further below a
strong station on the next AM channel will spoil the whole experience by
swamping the signal.

The Qu/Ql ratio determines the signal losses. a Qu/Ql=10:1 gives less
than 1 dB losses, a 2:1 ratio and the loss is a few decibels. A
500/100 ratio gives about 2 dB losses.

Which is close to impossible to even hear.

... In receivers with
amplification, this loss is directly added to the noise figure. For
this reason, it is undesirable to have too high loaded Ql in front of
the first amplifier stage. On the other hand, a wide front end can
easily overload the first amplifier or mixer. A high Ql filter between
the first amplifier and mixer helps a lot. This is an issue on VHF and
above.

The Q of the radio won't be the same as the Q of the components because
you are sucking off power to drive the headphones. Besides, the number
you came up with (10 kHz) would be perfect for AM radio if you can get
that, that is the channel spacing. Great selectivity.
It should be noted that BW = f / Q only gives the -3 dB point of the
response curve. There might be a 40-60 dB signal on the adjacent
channel, which will effectively kill the reception of the wanted
signal.

There is probably some sort of sports ambition where the guy with the
highest Q wins a trophy or at least a free beer

It *is* a hobby. No one builds a crystal radio set because he wants to
listen to talk radio.

This seems to be a US specific thing. In Europe, there are not much
local MF broadcasts any more. The situation was different 50 years
ago, but now it is hard to find a local LF/MF/HF transmitter within
1000 km, thus a simple crystal radio is more or less useless.

You comments indicate you neither understand the hobby

That is US country specific.

nor do you really
understand the technology, but I believe the latter is a choice on your
part. You seem to be deliberately refusing to try to understand what is
being said.

Why should I deliberately bang my head against the wall ?

Your comment above about not being able to hear a few dB is a good
example of your mindset.

1-2 dB of extra loss is significant in UHF EME (moonbounce)
communication, in which the amplifier itself has a noise figure in the
order of 1 dB (i.e. 100 K noise temperature). For any MF communication
circuits, the band noise is huge from location to location, from day
to day or from hour to hour, so a 1-2 dB variation doesn't really
cause problems.

Rather than trying to understand why anyone
would care if tweaking the core material for a coil adds a few dB, you
make a comment showing your disdain. Open your mind. Look at the
bigger picture. You tell me why anyone cares about the few dB from
optimizing this one feature?

I really do not understand why you make such fuss about LF, MF and
lower HF. However, those few decibels are of great concern in UHF/SHF
bands.

Nearly everything you wrote is not relevant to the conversation I have
been having. Why did you choose me to reply to? I was not addressing
you.

--

Rick C

Jeff Liebermann · Mar 30, 2017

On Wed, 29 Mar 2017 11:49:43 +1100, Clifford Heath
<no.spam@please.net> wrote:

Doubling the Q doubles the voltage and halves the current, four
times the impedance. It creates NO EXTRA POWER, except the tiny
1/Q resistive losses that are eliminated.

Umm... I beg to differ.
Q = Xl / R = Inductive_reactance / Resistance_and_losses
Assuming the inductance remains the same, changing the style of the
inductor, such as a ferrite core, loop antenna, Litz wire, scramble
wound solenoid, or honeycomb basketweave, will not change the
inductive reactance. Only the resistive and other losses part
dissipates power. Any change in Q will involve the resistive part of
the puzzle. For example, switching from magnet wire to Litz wire
offers an increase in surface area. Since RF conduction occurs on the
wire surface (skin effect), and Litz wire has a larger surface area,
the Q will be higher. A receiver design that doesn't over-load the
coil, where the losses from the load across the coil is substantially
greater than the dissipative losses from the coil resistance and
surface area, should be able to benefit from the increase Q by
recovering more power. Whether this appears as an increase in voltage
or current depends on how the power is "tapped" from the coil.

<https://en.wikipedia.org/wiki/Litz_wire>
"The ratio of distributed inductance to distributed resistance
is increased, relative to a solid conductor, resulting in a higher
Q factor at these frequencies."

I guess I should mention that Litz wire works well up to about 1MHz.
At higher frequencies, the eddy currents in the inside windings form,
creating additional losses which negate the benefits of using Litz
wire.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

rickman · Mar 30, 2017

On 3/28/2017 11:26 PM, Clifford Heath wrote:

On 30/03/17 12:40, rickman wrote:
On 3/29/2017 5:47 PM, upsidedown@downunder.com wrote:
On Wed, 29 Mar 2017 13:47:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the
detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few
dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

Why do you want to keep the receiver completely passive ?

A small solar cell o the headphone will charge a small battery, that
can be used to drive a small RF/IF/AF amplifier over the night.

How about a two circuit MF AM receiver, with one resonant circuit
tuned to your local strong MF (AM) station and the rectified DC power
is used to run the "DX" receiver ?

Why do you care what I do?

Because we don't have any convenient audiophools to ridicule,
but we can enjoy ridiculing radiophools.

You are doing nothing but making a fool of yourself.

--

Rick C

rickman · Mar 30, 2017

On 3/28/2017 11:23 PM, Clifford Heath wrote:

On 30/03/17 12:01, Jeff Liebermann wrote:
On Wed, 29 Mar 2017 10:18:33 +1100, Clifford Heath
no.spam@please.net> 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?

Because the added 3 inches will add equal amounts of signal and noise,
resulting in no net improvement. It's always fun to drag things to
their logical extreme. Instead of 3 inches, add 3 miles of wire. The
recovered energy will be huge and possibly sufficient to draw an arc.
But, so will the received atmospheric noise be huge by the same
amount. Besides less loss, a higher Q also means more selectivity, so
the receiver won't act the like the first crystal set I built in
middle skool, which received and demodulated most of the AM broadcast
band simultaneously. There's an upper limit to Q as set by the
modulation bandwidth. The AM broadcast band runs about 10KHz per
channel, so the maximum usable loaded Q would be:
Q = 1,000 KHz / 10 KHz = 100
Any Q more than 100 at BCB frequencies will begin dropping the higher
audio frequencies from the modulation. Too narrow band, and all you
can hear will be CW (Morse Code). There's also the problem of tuning
stability, where anything that causes the high Q coil to drift in
frequency, will produce even harmonic distortion of the audio. Copper
wire is not particularly temperature stable and will require some form
of frequency or tuning stabilization.

Ok, back to taxes...

If you aren't going to read the thread for context, then just stick with
your taxes.

We're talking about increasing Q above where it starts to exclude
some of the signal frequencies. Of course there is also noise
excluded in that process, but that's unlikely to improve SNR.

Please follow your own advice. You and Joerg are the only posters here
who are saying the high Q of the coil will impact the bandwidth. We
have patiently explained to you that the Q of the receiver will *NOT* be
as high as the Q of the antenna and will not adversely impact the
bandwidth of the received signal.

--

Rick C

rickman · Mar 30, 2017

On 3/29/2017 5:47 PM, upsidedown@downunder.com wrote:

On Wed, 29 Mar 2017 13:47:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/28/2017 11:12 AM, 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. But before you do that match,
you need to insert a diode to demodulate the signal
The diode adds a series resistance into the circuit, that is
before the matching audio transformer.

Somewhere in the process of being in this discussion I cam across a web
site (perhaps Kleijer's) that deeply analyzed the losses in the detector
diode. I we pretty impressed.

Save a few dB in the coil, a few dB in the tuning capacitor, a few dB in
the diode and use a very sensitive pair of headphones and you have a
*much* improved radio!

Why do you want to keep the receiver completely passive ?

A small solar cell o the headphone will charge a small battery, that
can be used to drive a small RF/IF/AF amplifier over the night.

How about a two circuit MF AM receiver, with one resonant circuit
tuned to your local strong MF (AM) station and the rectified DC power
is used to run the "DX" receiver ?

Why do you care what I do?

--

Rick C

Mar 30, 2017

On Wednesday, 29 March 2017 01:10:27 UTC+1, tabby wrote:

I've not done an inductorless class D before. This will be under 1w of output, run off expensive battery power sometimes, and will be budget critical. The question is what frequency to pick.

What's the lowest frequency one could be run at? What percentage of random small transistors could operate adequately at that frequency?

I'm looking primarily for minimum cost & maximum transistor compatibility, and secondarily for low current consumption. A degree of sound quality compromise is ok, these will be running fairly small speakers.

NT

Maybe I'll have to build it & see.

NT

Mar 31, 2017

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?

Cheers,
James Arthur (who has *no* dog in this fight!)

Mar 31, 2017

ĺ¨ 2013ĺš´11ć26ćĽććäş UTC+8ä¸ĺ3:29:40ďźamdxĺéďź

On 11/25/2013 2:02 AM, Jeff Liebermann wrote:
On Mon, 25 Nov 2013 01:41:20 -0500, Spehro Pefhany
speffSNIP@interlogDOTyou.knowwhat> wrote:

I've got a Wemo device in use now, pretty slick stuff. I can switch my
lights on and off from Jena Germany or China, with confirmation (if I
don't want to look at the webcam).

http://www.belkin.com/us/wemo
Kinda expen$ive. Uses wi-fi to communicate, not power lines. Supports
IFTTT.
https://ifttt.com/wtf
A major step up from X10. However, it might be a bit overkill for a
3-way light switch.

How to turn on a room light:

1960: Walk over to wall switch. Flip switch. Light turns on.

1975: Find the X10 wireless remote control. Try to remember which
button controls which light. Press button. Wrong light. Press "all
on" and never mind the electric bill.

2003: Say the magic buzzword that activates the voice controlled home
automation system.
You say: "Room light on".
Controller asks: "Which room"?
You say: "Can't you figure out which room I'm in"?
Controller says: "I do not understand the command".
You snarl: "Bedroom"
Controller asks: "Bright, reading, soft, or motion controlled"?
You say: "Bright" and the lights turn on.
You say (quietly): "Worthless piece of disgusting junk..."
Controller says: "I do not understand the command".
Sound of breaking glass as something hits the LCD display.

2013: Walk into dark room and try to find your tablet computer. Login
with biometric authentication and password. On the 4th try, the
tablet finally recognizes your hung over, unshaven, and unkempt
appearance. Wait while a dozen applications insist on updating
themselves immediately. Find the WeMo light switch app among the
dozen new games the kids have installed. Push the relevant light
switch button. Nothing happens. Try again. Still nothing. Pause
watching Netflix Super-HD movie to recover bandwidth. Try again.
Light comes on.

This is progress?

And all I want is a switch that will turn the kitchen light on and
off, from about 18 ft away without, and I don't want to add wiring.
I want it to act like what normally is called a 3* way switch.
I want the existing kitchen switch to at least look about the same,
being aware that the wiring/components may be different.
I would like it to drive a CFL bulb.
This model has a huge presence on the web,
http://www.walmart.com/ip/Chamberlain-BL-6133-WH-BL-6133-WH-Wireless-Add-On-Switch-Set/17101311
I says 500 watt incandescent lighting only. I see writings about these
types of receivers needing some leakage current, I'm tempted to get one
and try it.
At this point I have remote switch overload.

Thanks all, Mikek

*Searching the net I see, 2 way switch and 3 way switch are often used
to describe the same thing

We supply wireless self-powered switch which without wiring, using battery or wifi, at the same time you can use your phone to do remote control.

Please feel free to contact us if you have any questions. Your prompt reply will be highly appreciated.
Gaby Kong
Email: gabykong@didiok.org
Skype:gabykong.1
Wechat/QQ : 407573144
WhatsApp: +86 13148950830

Neon John · Apr 1, 2017

On Tue, 28 Mar 2017 15:19:59 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

My application is a backup "portable" generator. One useful feature of
CDI in this application is that it doesn't require a large input
current, meaning that I can start the generator using cheap dry cells,
and then let it power itself. No need for limited life failure prone
rechargeable batteries that need to be kept topped up lest they die.

And the problem with CDI, which several motorcycle manufacturers and
Mercury Marine discovered the hard way, is that the brief spark is
lousy at igniting less than optimum mixtures. Sure, it'll fire a plug
dipped in oil but it won't fire a non-optimum mixture. Something
common when trying to crank an engine under adverse conditions.

The MSD (Multiple Spark Discharge) company solved this problem by
firing up to 8 sparks per ignition event. That company has been
around for 30 or 40 years now.

I suggest that you scrap that circuit and go back to the pulse
triggered Kettering-type ignition. A GM HEI module from the 70s up
through when they gained a 5th terminal makes an EXCELLENT controller.
IT will work with points, variable reluctance or pulse input. Adding
external inductance in parallel with the coil will lengthen the spark
and make it more likely to ignite a crappy mixture.

A brand name AGM battery (Enersys Odessey for example) will maintain
most of its charge for a year or more and a Battery Tender costs
almost nothing.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

Jim Thompson · Apr 1, 2017

On Fri, 31 Mar 2017 14:41:00 -0400, Neon John <no@never.com> wrote:

On Tue, 28 Mar 2017 15:19:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

My application is a backup "portable" generator. One useful feature of
CDI in this application is that it doesn't require a large input
current, meaning that I can start the generator using cheap dry cells,
and then let it power itself. No need for limited life failure prone
rechargeable batteries that need to be kept topped up lest they die.

And the problem with CDI, which several motorcycle manufacturers and
Mercury Marine discovered the hard way, is that the brief spark is
lousy at igniting less than optimum mixtures. Sure, it'll fire a plug
dipped in oil but it won't fire a non-optimum mixture. Something
common when trying to crank an engine under adverse conditions.

The MSD (Multiple Spark Discharge) company solved this problem by
firing up to 8 sparks per ignition event. That company has been
around for 30 or 40 years now.

Yep. I devised schemes to do just that when I was at Philco-Ford in
1968 and Dickson Electronics 1970-72... works quite well with this
"self-inverting" method....

<http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>

I suggest that you scrap that circuit and go back to the pulse
triggered Kettering-type ignition. A GM HEI module from the 70s up
through when they gained a 5th terminal makes an EXCELLENT controller.
IT will work with points, variable reluctance or pulse input. Adding
external inductance in parallel with the coil will lengthen the spark
and make it more likely to ignite a crappy mixture.

A brand name AGM battery (Enersys Odessey for example) will maintain
most of its charge for a year or more and a Battery Tender costs
almost nothing.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

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