Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

"David" wrote in message
...
Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

Hi David,
I don't think it really works that way. The audio is level is dependent on
the level of the RF signal.
Get a long antenna and sensitive headphones.
Check the http://members.shaw.ca/ve7sl/crystal.html
and see the list at the bottom, check out Rap N Tap.
Mike

David wrote:
Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

If you are quadrupling the voltage at the headphones, then you are, of
necessity, dividing the impedance at the detector by a factor of 16.

You only have so much power available at the antenna; a detector
followed by an unpowered "voltage quadrupler" won't extract any more
power than any other equivalently-well-matched detector, and so won't
put any more power to the headphones.

If you really want to do this passively, and not rely on some near-by
strong station for power, then you need to optimize your circuit and
headphones for efficiency, and you need to get a _lot_ of wire into the air.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

"David" wrote in message
...
Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

It is better to play with the design to achieve the desired matching between
the tuner, detector and headphones. Diodes have losses, and fancy
circuits like your suggesting will only multiply the losses, not the
voltage.

Pete

"David" wrote in message
...
Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

I don't have a circuit, but have seen where a transistor was powered by a
rectified radio signal to boost the audio signal. I think a seperate
antenna and tuned circuit was used on the strongest signal in the area.

On Mon, 20 Apr 2009 11:34:49 -0700 (PDT), David
wrote:

Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

I assume you are talking about a broadcast receiver for frequencies
below 1600 kHz. At such frequencies and with a typical 500 pF variable
capacitor, the impedance levels for an LC resonant circuit is quite
high.

Loading it with a crystal detector and some low impedance (30 or less)
headphone will load the resonant circuit quite heavily, reducing the
output quite heavily.

In the old days, the typical impedance of a headphone might have been
about 2000 ohms, loading the resonant circuit much less. In order to
cause a similar loading to the resonant circuit using current
headphones, you need an audio transformer with 2000:30 impedance ratio
or 8:1 turns ratio.

Paul OH3LWR

On Apr 20, 6:20*pm, Tim Wescott wrote:
David wrote:
Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

If you are quadrupling the voltage at the headphones, then you are, of
necessity, dividing the impedance at the detector by a factor of 16.

You only have so much power available at the antenna; a detector
followed by an unpowered "voltage quadrupler" won't extract any more
power than any other equivalently-well-matched detector, and so won't
put any more power to the headphones.

If you really want to do this passively, and not rely on some near-by
strong station for power, then you need to optimize your circuit and
headphones for efficiency, and you need to get a _lot_ of wire into the air.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details athttp://www.wescottdesign.com/actfes/actfes.html

Hey OM:

What you claim may be true, but if I use a pair of 2000 ohm headphones
and have 100 millivolts into those phones, I would developed a power
into those headphones of 5 microwatts. Now if the voltage goes up 4
times to 400 millivolts the power developed into the phones is 80
microwatts. So it don't matter what the detector impedance is. The
headphones don't care what the impedance is, in this case.

Now if the detector impedance was 10,000 ohms then you have a
problem.

So basically is it optimized for say Edison electric to run a 50 amp
main to my house when I only use a 100 watt light bulb? The source
impedance is a lot lower than my 100 watt light bulb.

Don't forget a good ground connection also.

73 OM

de N8ZU

On Apr 20, 7:40*pm, Paul Keinanen wrote:
On Mon, 20 Apr 2009 11:34:49 -0700 (PDT), David
wrote:

Looking for Crystal Radio Receiver Circuits, that have a voltage
quadrupler to increase headphone volume without batteries or AC power.

I assume you are talking about a broadcast receiver for frequencies
below 1600 kHz. At such frequencies and with a typical 500 pF variable
capacitor, the impedance levels for an LC resonant circuit is quite
high.

Loading it with a crystal detector and some low impedance (30 or less)
headphone will load the resonant circuit quite heavily, reducing the
output quite heavily.

In the old days, the typical impedance of a headphone might have been
about 2000 ohms, loading the resonant circuit much less. In order to
cause a similar loading to the resonant circuit using current
headphones, you need an audio transformer with 2000:30 impedance ratio
or 8:1 turns ratio.

Paul OH3LWR

Hey OM

I know they still make 2000 ohm headphones, Philmore still makes them,
then there is a crystal headphone.
A crystal headphone you can make yourself. It''s just a crystal
microphone in reverse. I seen the QST article on how to make a crystal
microphone.

But the best bar none, is a balanced armature headphones, those things
are self powered, or so they say. And balanced armature headphones
cost an arm and a leg too.

73 OM

de n8zu

raypsi wrote:

Hey OM:

What you claim may be true, but if I use a pair of 2000 ohm headphones
and have 100 millivolts into those phones, I would developed a power
into those headphones of 5 microwatts. Now if the voltage goes up 4
times to 400 millivolts the power developed into the phones is 80
microwatts. So it don't matter what the detector impedance is. The
headphones don't care what the impedance is, in this case.

Yes it does. And no, your math is wrong. Phones don't respond to watts.

In a simple crystal radio the voltage is gained by NOT loading down the
preceeding circuit. If you load down a simple LC circuit with a
doubler/quadrupler as opposed to 'one clean diode' then you lose more
than you gain. And you take an additional hit on selectivity because
the Q of the RF circuit becomes loaded excessively. Thats why the
doubler/quadrupler schemes that look good on paper don't pass muster
with xtal radio enthusiasts.

Detector impedance, headphone impedance are the meat and potatoes in
"dx" crystal radio circuits. Its a house of mirrors, so to speak.
Poor impedance match at the fones will kill RF selectivity, for example.
Yes, you have to look at it that way.

Doesn't matter much with a Rocket Radio or a Cub Scout radio but if you
get into the high end of xtal sets its very important.

-Bill

On Apr 21, 11:14*pm, Bill M wrote:


. *Phones don't respond to watts.


-Bill

Hey OM:

Thanks for the sardonic epiphany.

73 OM

de n8zu