A Couple of Questions About A Crystal Set
 

I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.

"-" wrote in message
...
I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.


No to SSB... it requires a carrier signal to be reinserted.

Yes to being able to make modifications (usually a coil change) for 30 MHz
reception.

- wrote in news:E%hpb.123250$Hs.62791
@twister.nyroc.rr.com:

http://www.vintageradio.info/xtal-modern.html
http://www.crystalradio.net/crystalplans/index.shtml
http://www.midnightscience.com/
http://members.aol.com/scottswim/larry.htm

Hope this helps in your endeavors.

Dr. Artuad


I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.




--
To know and to be, this is not even a question, there is no alternative.
You see it clearly in the loneliest little avenues between particles and
waves, shunned even by the gregarious quark and unknown by the various
strands of time, so big it cannot be seen, yet so little it is immovable,
lies the fabric of the ultimate reality gripped in the fist of the all or
nothing."

NoSpam,

Take a look at these "Homemade Crystal Radios" by Digtal Dave
http://www.schmarder.com/radios/index.htm
Looking at his radios shows that he is both a Craftsman and Artist.


~ RHF
..
..
= = =
= = = wrote in message . ..
I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.

1) No. 2) Maby but I've never be able to do it. Check out the crystal set
society. Thay have a web site. And several books you can get on crystal
sets. Crystal sets work better on MW than SW. But you can pick up SW
stations with them. Also Check out Modern Radio Laboratories. Thay have a
web site and a yahoo group.

Bill, N5NOB

- wrote in message
...
I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.


You may not be able to receive SSB with a crystal set but give Morse code a
try, you might have better success. Can you figure out a simple way to do
it?
;-)

RG

"RadioGuy" wrote in message
...

- wrote in message
...
I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive" characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.


You may not be able to receive SSB with a crystal set but give Morse code
a
try, you might have better success. Can you figure out a simple way to do
it?
;-)

RG


Morse is pretty easy with a crystal set.. that's what foxhole radios were
for. You don't get a tone, which makes it a little harder to copy, but you
can just listen for the carrier keying, all the intelligence is there even
without a tone.

Brenda Ann wrote in message
...

"RadioGuy" wrote in message
...

- wrote in message
...
I am intrigued with the idea of a totally passive reciever -one that
requires no power source- and so find myself looking into building a
crystal set for myself. I found what appears to be a pretty easy
build-up at this page: http://antiqueradio.org/econmain.htm

To my non-expert eye, it appears to be a very well thought out, clever
design.

My questions a

1. Is it possible to modify the design to also allow for the clear
reception of ssb signals while maintaining the "passive"
characteristic
that I find so appealing?
2. Would it be difficult to modify the design to allow reception above
the stated ~17Mhz upper limit to, say, 30Mhz?

Any input/thoughts will be much appreciated.


You may not be able to receive SSB with a crystal set but give Morse
code
a
try, you might have better success. Can you figure out a simple way to
do
it?
;-)

RG


Morse is pretty easy with a crystal set.. that's what foxhole radios were
for. You don't get a tone, which makes it a little harder to copy, but
you
can just listen for the carrier keying, all the intelligence is there even
without a tone.



With the proper hookup you will get a tone---and the tone will be adjustable
in frequency depending upon operator preference.

I thought Foxhole radios were field expedient devices using an oxide
finished razor blade (Gillete) and pencil point for detector---in the usual
crystal set hookup. The radios were used by US service men in combat
overseas WWII to receive local AM broadcasts. I have a copy of a Foxhole
radio article that appeared in a 1948 (?) issue of QST authored by a fellow
who served in the Pacific theatre somewhere in my files.

OK... how many of you fellows cut your fingers on that razor blade building
that set? It got me more than once!

BTW... I'm RadioGuy and I'm BACK! HELLO ALL!

RG

To go higher in frequency would require a diode capable of higher frequency.

My first crystal set, a Philmore, used a galena detector. My second one used an
out of spec microwave diode (1N23). G

CW, the original digital communications, may be copied, because the on-off
action would vary any noise.

Bill, K5BY

"RadioGuy" wrote in message
...
With the proper hookup you will get a tone---and the tone will be
adjustable
in frequency depending upon operator preference.

Ah, but then it wouldn't be a totally passive receiver. The OP is looking to
use only the passive receiver, not any add-ons or external sources.

Brenda Ann wrote in message
...

"RadioGuy" wrote in message
...
With the proper hookup you will get a tone---and the tone will be
adjustable
in frequency depending upon operator preference.

Ah, but then it wouldn't be a totally passive receiver. The OP is looking
to
use only the passive receiver, not any add-ons or external sources.


Yes well... I can't say the receiver will be totally passive but it won't be
too much more complicated than the basic crystal detector. At the most,
roughly speaking, three more component parts will be needed.

RG

WShoots1 ) writes:
To go higher in frequency would require a diode capable of higher frequency.

My first crystal set, a Philmore, used a galena detector. My second one used an
out of spec microwave diode (1N23). G

Of course, a real problem with a "crystal radio" is that it's only got
one tuned circuit at the front end. Long before the diode becomes an issue,
the fact that that single tuned circuit will be pretty wide as you go up
in frequency will be a significant factor. Even at AM broadcast frequencies,
the selectivity of most "crystal radios" is marginal.

On the other hand, selectivity may not be a real issue as you move up in
frequency, since sensitivity is also an issue with "crystal radios". They
work with local stations because those stations are relatively strong.
Move higher than 1600KHz, the top of the AM broadcast band, and most people
will not come across local stations, so anything that is heard will be weak,
and have to be a pretty strong signal to begin with. In that context,
selectivity may not be a real issue, since there will only be a handful
of signals that can be received anyway.

Michael

"RadioGuy" wrote in message
...


Yes well... I can't say the receiver will be totally passive but it
won't be
too much more complicated than the basic crystal detector. At the
most,
roughly speaking, three more component parts will be needed.

RG



Demodulating SSB/CW is theoritically possible with an entirely passive
circuit. If there's a very high Q circuit at the proper frequency, it
will ring enough to give a good sidetone to CW and even demodulate SSB.
I have a couple of old single crystal filter receivers that can do just
that. Tuning is very touchy, and it takes alot of signal, especially
for SSB.

You'd need a proper frequency crystal, or a very, very, very, large
tuned cavity for starters. Being within the shadow arc of a powerful
SSB/CW transmitter would also be helpful. As a practical matter, it's
best done as a mind exercise.

Frank Dresser

"Brenda Ann" ) writes:
"RadioGuy" wrote in message
...
With the proper hookup you will get a tone---and the tone will be
adjustable
in frequency depending upon operator preference.

Ah, but then it wouldn't be a totally passive receiver. The OP is looking to
use only the passive receiver, not any add-ons or external sources.


Maybe he's talking about a bit of DC bias, and kicking the diode into
oscillation. There were reports of that sort of thing happening when
"crystal radios" were still pretty important.

Likely finicky, if one can get a specific diode to oscillate, and no
it's no longer passive, but it is simpler than the obvious solution of
adding an extra beat oscillator.

Michael

Maybe he's talking about a bit of DC bias, and kicking the diode into
oscillation. There were reports of that sort of thing happening when "crystal
radios" were still pretty important.

Now that you mention it, I believe that technique was used in some modern
device. Hmm... Possibly something in the UHF range...

Bill, K5BY

"WShoots1" wrote in message
...

Now that you mention it, I believe that technique was used in some
modern
device. Hmm... Possibly something in the UHF range...

Bill, K5BY

A tunnel diode? As I understand, that was supposed to be the "Next Big
Thing" around 1960. Didn't work out that way. But Heathkit did sell a
few "Tunnel Dipper" GDO type meters.

Frank Dresser

Michael Black wrote:

WShoots1 ) writes:
To go higher in frequency would require a diode capable of higher frequency.

My first crystal set, a Philmore, used a galena detector. My second one used an
out of spec microwave diode (1N23). G

Of course, a real problem with a "crystal radio" is that it's only got
one tuned circuit at the front end. Long before the diode becomes an issue,
the fact that that single tuned circuit will be pretty wide as you go up
in frequency will be a significant factor. Even at AM broadcast frequencies,
the selectivity of most "crystal radios" is marginal.

On the other hand, selectivity may not be a real issue as you move up in
frequency, since sensitivity is also an issue with "crystal radios". They
work with local stations because those stations are relatively strong.
Move higher than 1600KHz, the top of the AM broadcast band, and most people
will not come across local stations, so anything that is heard will be weak,
and have to be a pretty strong signal to begin with. In that context,
selectivity may not be a real issue, since there will only be a handful
of signals that can be received anyway.

Michael

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?


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"starman" wrote in message
...

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?


There was a circuit, very simple, for a germanium diode receiver for the FM
broadcast band. Basically, it consisted of a large loop and variable
capacitor making up the tuned circuit, a germanium diode, a resistor, a 100
pF disc cap, and a crystal earphone. Tuning was by slope detection,
although I can't see why such a device could not be made into a ratio
detector by center tapping the coil (or making two identical coils, and
tapping between them). Also no reason that you could not listen to an
airplane's broadcasts on such a device with the loop cut to those
frequencies.

As for the law, I don't think there actually IS one, only a convention
disallowing use of radio receivers/transmitters onboard commercial flights.
The reason for this is because the local oscillator of an FM radio falls
directly in the aircraft comms band anywhere above 97.4 MHz. A crystal
radio would not interfere, and would be impossible to detect. One for such
close proximity to the transmitter could be just a small coil, instead of
the loop, and could be built into something like a pocket radio case.

starman wrote in message
...
Michael Black wrote:

WShoots1 ) writes:
To go higher in frequency would require a diode capable of higher
frequency.

My first crystal set, a Philmore, used a galena detector. My second
one used an
out of spec microwave diode (1N23). G

Of course, a real problem with a "crystal radio" is that it's only got
one tuned circuit at the front end. Long before the diode becomes an
issue,
the fact that that single tuned circuit will be pretty wide as you go up
in frequency will be a significant factor. Even at AM broadcast
frequencies,
the selectivity of most "crystal radios" is marginal.

On the other hand, selectivity may not be a real issue as you move up in
frequency, since sensitivity is also an issue with "crystal radios".
They
work with local stations because those stations are relatively strong.
Move higher than 1600KHz, the top of the AM broadcast band, and most
people
will not come across local stations, so anything that is heard will be
weak,
and have to be a pretty strong signal to begin with. In that context,
selectivity may not be a real issue, since there will only be a handful
of signals that can be received anyway.

Michael

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?

Yes... I remember reading a construction article circa 1959 (I think) in
Popular Electronics that used such a device to listen to aeronautical coms
within the passenger compartment. It was a basic diode detector mounted in
a pocket-sized plastic box. The antenna was a loop wrapped around the box.
I can't remember if there was an audio amplifier. Since it did not radiate
a signal it was viewed as allowable for use inside the aircraft; that was
the rationale expressed in the article back then---in a safer, tamer and
saner world! However, try it now at your own risk ;-)

I think the article even went on to suggest that you show your handicraft to
the stewardess HA! HA! HA!

RG

starman ) writes:
Michael Black wrote:

WShoots1 ) writes:
To go higher in frequency would require a diode capable of higher frequency.

My first crystal set, a Philmore, used a galena detector. My second one used an
out of spec microwave diode (1N23). G

Of course, a real problem with a "crystal radio" is that it's only got
one tuned circuit at the front end. Long before the diode becomes an issue,
the fact that that single tuned circuit will be pretty wide as you go up
in frequency will be a significant factor. Even at AM broadcast frequencies,
the selectivity of most "crystal radios" is marginal.

On the other hand, selectivity may not be a real issue as you move up in
frequency, since sensitivity is also an issue with "crystal radios". They
work with local stations because those stations are relatively strong.
Move higher than 1600KHz, the top of the AM broadcast band, and most people
will not come across local stations, so anything that is heard will be weak,
and have to be a pretty strong signal to begin with. In that context,
selectivity may not be a real issue, since there will only be a handful
of signals that can be received anyway.

Michael

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?

Some "crystal radios" for the aircraft band were described in the hobby
magazines thirty and so years ago. They specifically used the "it doesn't
radiate, so it's safe on an aircraft". I never saw a third party opinion
on it; clearly it is safer than borderline things that are allowed on,
but I have no idea if the rules actually specify specs, or a need to
meet specs.

The articles did say they worked well on the airplane, though what
you heard was mostly transmissions from the aircraft rather than ground.
The lack of selectivity in this case was not a consideration, since you
wanted to hear it all.

Michael

I have a sneaking suspicion that the main reason that commercial airliners
don't allow cellular phone use is so that you'll have to use the expensive
one they provide in the back of the headrests. But then, I'm a cynical kind
of guy ;^)

-- Stinger
"Brenda Ann" wrote in message
...

"starman" wrote in message
...

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?


There was a circuit, very simple, for a germanium diode receiver for the
FM
broadcast band. Basically, it consisted of a large loop and variable
capacitor making up the tuned circuit, a germanium diode, a resistor, a
100
pF disc cap, and a crystal earphone. Tuning was by slope detection,
although I can't see why such a device could not be made into a ratio
detector by center tapping the coil (or making two identical coils, and
tapping between them). Also no reason that you could not listen to an
airplane's broadcasts on such a device with the loop cut to those
frequencies.

As for the law, I don't think there actually IS one, only a convention
disallowing use of radio receivers/transmitters onboard commercial
flights.
The reason for this is because the local oscillator of an FM radio falls
directly in the aircraft comms band anywhere above 97.4 MHz. A crystal
radio would not interfere, and would be impossible to detect. One for such
close proximity to the transmitter could be just a small coil, instead of
the loop, and could be built into something like a pocket radio case.

"Stinger" ) writes:
I have a sneaking suspicion that the main reason that commercial airliners
don't allow cellular phone use is so that you'll have to use the expensive
one they provide in the back of the headrests. But then, I'm a cynical kind
of guy ;^)

-- Stinger

Huh? There were rules in place a long time before cellphones to deal
with the issue of electronic equipment being used by passengers on airplanes.

At some point, it became an issue, or someone forsaw it being an issue.
That was back in the days when the average person would only have
an AM/FM radio. But it was in place by the early seventies; definitely
before but that's when I first started hearing about it. Radio equipment,
and more recently many pieces of non-radio electronic equipment, could
radiate signal that might interfere with with airplane communication
and/or navigation, so better to be safe than sorry.

Michael


"Brenda Ann" wrote in message
...

"starman" wrote in message
...

Anyone built a passive receiver for VHF or UHF? Could you listen to an
aircraft's communications as a passenger on the same plane? What does
the law say about using any aircraft receiver on a plane, whether it's
passive or active?


There was a circuit, very simple, for a germanium diode receiver for the
FM
broadcast band. Basically, it consisted of a large loop and variable
capacitor making up the tuned circuit, a germanium diode, a resistor, a
100
pF disc cap, and a crystal earphone. Tuning was by slope detection,
although I can't see why such a device could not be made into a ratio
detector by center tapping the coil (or making two identical coils, and
tapping between them). Also no reason that you could not listen to an
airplane's broadcasts on such a device with the loop cut to those
frequencies.

As for the law, I don't think there actually IS one, only a convention
disallowing use of radio receivers/transmitters onboard commercial
flights.
The reason for this is because the local oscillator of an FM radio falls
directly in the aircraft comms band anywhere above 97.4 MHz. A crystal
radio would not interfere, and would be impossible to detect. One for such
close proximity to the transmitter could be just a small coil, instead of
the loop, and could be built into something like a pocket radio case.

A tunnel diode?

That's it, Frank. Thanks.

Were they used in early TV UHF tuners?

Bill, K5BY

"WShoots1" wrote in message
...

Were they used in early TV UHF tuners?

Bill, K5BY

I don't think so. As I understand, they did work well at UHF
frequencies, but the circuits were very touchy to keep working. There
was alot of excitement for the tunnel diode in the old magazine articles
of around 1960, but it was quickly overshadowed by improved conventional
transistors.

Frank Dresser