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Archive 1 |
Will add a How-to section in the next few days. — Preceding unsigned comment added by Robertkeller ( talk • contribs) 06:00, 23 May 2003
It appears awkward to call this article Crystal Radio Receiver instead of the normal term of reference of Crystal Radio. I propose we move it to Crystal Radio and redirect Crystal Radio Receiver to it just in case anyone ever searches for the "Receiver" version.
John 15:22, 17 November 2006 (UTC)
The lead section is confusing, especially to laymen, I would like to omit jargon like "LC". Many simple crystal radios do not even use variable capacitors for tuning. Crystal radios use a variety of circuits and to present one circuit as defining could be misleading; the lead section should be more generic and inclusive of all that is crystal radio. It is also somewhat wrong in presenting "LC" tuning as the simpliest because inductor-only tuning is simplier than the "LC" tuning. If no one objects I plan to offer an improved, simplier, jargon-free more technically accurate, and more aware lead section wording. -DONE
John 06:14, 12 November 2006 (UTC)
That is a beautifully built artistic radio by VE6AB but in my opinion it is not as representative of crystal radio as an old one. Also, I am concerned that it is a bit commercial because it is offered for sale too. I propose to substitute a photo of a simple-minded, strictly functional old one-slider radio with an open cat whisker detector if I can find one.
John 15:19, 17 November 2006 (UTC)
Why is this awkwardly called Crystal Radio Receiver instead of the normal term of reference of Crystal Radio? I propose we move it to Crystal Radio and redirect Crystal Radio Receiver to it just in case anyone ever searches for the "Receiver" version.
John 15:22, 17 November 2006 (UTC)
Added a simple-minded explanation of how it works. Although I have posted a similar explanation elsewhere, I am the original author and I have the right to post it here and hereby declare that I release all copywright to it.
John 15:58, 17 November 2006 (UTC)
The page referenced by "Crystal Connections" is closed. We could remove it, or leave it in until web rot gives us a 404 not found.
The capacitor should be BEFORE the detector so that it forms a resonant (tank) circuit with the coil. The circuit diagram shows the capacitor after the detector: I'm sure this is wrong.
The design shown is correct! It is the classic "Fox hole" radio. The coil tunes using a slider connection and resonates against the capacitance of the antenna. This design was used because Variable Caps were not available to the builders (eg soldiers in trenches).
To put it another way, the capacitance of a long wire antena is quite large. This capacitance will swamp a normal tuned circuit and will prevent the tuning cap covering the band. At the very least the antenna needs to be tapped well down the coil or coupled in via a small value cap in series. The solution to all this was to delete the tuning cap, and instead adjust the number of turns in the coil (as shown correctly in the diagram).
BTW, the small cap shown is to bypass the RF after the detector. It is not really necessary.
The capacitor symbol is wrong (should have only two bars), but again, it attempts to show a "homemade" cap (perhaps made from layers of tinfoil from a bubblegum wrapper).
The mention of "ultra-thin litz wire inductors" is clumsy. It should be something like "many thin strands". Also Litz is NOT a new idea. It is very old.
The reference to the Pixie-2 is wrong. It's receiver is NOT a crystal set, it is a "Direct Conversion" set using an "Active Mixer".
The reference also seems to confuse Crystal Oscillators with Crystal detectors. These are two very different things.
This section seems to lack focus. Is the title of this section appropriate? It does not seem to address how to construct a 'crystal radio'. Is it intended to address the components that make it up? How they are connected? How it works or what? I think it would be helpful to figure out what this section is doing, do it and name it appropriately.
John 15:33, 17 November 2006 (UTC)
Not sure what the Construction section is doing but it has a number of problems: It introduces the concept of the simplest radio yet fails to use the simplest circuit, (which should be a coil without the tuning capacitor across it.) If someone actually builds this for the Broadcast Band, it will not tune the whole band because of the fixed antenna capacitance across the variable capacitor. Some mineral detectors are not crystals, like Lead Peroxide. Cadmium sulphide is not a reasonably good detector. The detector does not need to be (and not even typically) mounted in a brass cup (it is typically potted in Woods metal.) The cost of the antenna wire is off topic. The “…provides audio output in proportion to signal strength of signal …” is misleading in 2 ways. The “passive” and “no amplification” is redundant. The statement about “no way to control volume” is not necessarily factual. The paragraph about detection efficiency is rambling.
Anyone think we should keep this section?
John 05:08, 19 April 2007 (UTC)
Never mind that the circuit was correct, especially for a very early set. It was also the circuit of the famous Boy Scouts "slider coil" radio.
Have a look at the photo at the top right of the page. Can you see a tuning capacitor? For "clarity" you should remove that photo as well.
And by the way, it isn't a photo of a "modern set", its a re-creation of a very old set, from before the days when tuning capacitors were readily available.
This diagram?
What is confusing about it?
69.76.192.205 20:06, 24 December 2006 (UTC)
Answer to 69.76.192.205 question: what is confusing about the above diagram: Except for antenna and ground, all of the schematic symbols are non-standard, they are made up in such a way that they are not symbolic enough of the parts to wikify. These are not even antique versions of the symbols. Why not use standard symbols so all can understand? John 05:23, 19 April 2007 (UTC)
really they are all easy to understand. Capacitor ... antenna ... crystal rectifier ... headphones ... and the ground ...
J. D. Redding
02:57, 11 May 2007 (UTC)
Oh yea .. forgot to say ... thereis a rheostat coil there too ... J. D. Redding
Reply to J. D. Redding. Why use non-standard symbols? We don't need to make up symbols; it demonstrates lack of knowledge and cannot be researched (except for the antenna symbol.) We should not be introducing readers to incorrect symbols. This should be changed to a wiring pictorial or a valid schematic. Besides being out of place and unreferenced, there are technical problems with this diagram. The antenna and detector should be connected to the same point on the coil, or in a more complex circuit the detector connection separately adjustable. The capacitor is for VLF use only, and invites confusion with use as a tuning capacitor. Does it have enough value to retain? Can we fix and reference it or delete it? John 20:38, 15 May 2007 (UTC)
Technical problems with this diagram? What? This is one of the many different types of crystal radio circuits (not recognizing this is something that demonstrates a lack of knowledge about crystal radios). The circuit works too ... because this is the one I built and received sound on. No need to "fix" something that is not broken ...
This is symbols that are used in various crystal radio diagrams. Have you looked at alot of crystal radio diagrams from the 1920s up to now? These symbols have been used ... and can be used. Does not have to be a certain "wiring pictorial" or a certain type of schematic. Do you wanna change the G. W. Pickard picture because he isn't using "valid schematic". J. D. Redding 21:59, 17 May 2007 (UTC)
It has been suggested that crystal radios may still be in use by spies. This may be because crystal sets have no local oscillator so a counter-espionage organisation cannot determine that any receiver is being used by picking up the local oscillator frequency. This is a bit silly since various categories of receivers have no oscillators (e.g. TRF, Regen) and their much higher performance would be greatly prefered over a crystal set. by -- Light current 00:34, 8 September 2006 (UTC)
The following section has been twice removed from the article, however the reasons of removing seem not convincible for the contributor: The diode detector is not effective, as for weak signals (that must be rectified) the forward and reverse conductivity of the diode differs much less than it would differ for the stronger current. For the signal lever is between 20 - 100 mV, the transmission coefficient of the diode detector varies from 0.12 till as low as 0.01 [1]. The alternative methods of detection using transistors are also known. In the simpliest case, the base and emitter of the pnp bipolar transistor are connected together, and to the radio signal source. The detected radio signal is taken from collector. The transistor, connected this way can be up till 6 times more effective than diode.
Radio was the leading amateur journal in the Soviet Union and should count as a reliable source. Also, from the characteristic of the semiconductor diode in Wikipedia it is also self evident that forward and reverse conductivity does not differ much for the weak signals. Audriusa 15:36, 27 January 2007 (UTC)
It is true that a diode is an inefficient detector for weak signals (it operates in the Square Law mode). However the connection as described simply does not work. Shorting the base and emitter of a transistor produces a normal diode at the collector junction. Gutta Percha
I removed the above referenced part one of those times mostly because it was hard to understand because of grammatical and technical problems, which were subsequently improved. It is still a little flaky, however, wouldn't you agree a B-E junction of some transistors have a very sharp (non-square law) avalanche in reverse bias (ie. needs a battery!) mode, which can sometimes be more efficient than unbiased detection. John 06:47, 27 February 2007 (UTC)
No. You describe an Avalanche diode, which is an active device. The radio is then no longer a Crystal set. Gutta Percha 10:04, 13 June 2007 (UTC)
The Crystadyne section is facinating, but not squarely on topic for this article. It is an early discovery of solid state amplification instead of passive crystal radio. I plan to remove it and create a new stand alone article with it if there are no objections. John 22:02, 10 May 2007 (UTC)
Good Idea. In the early days there were many references to amplification using crystal detectors with multiple "catswhiskers" and bias. It is clear that Schottky was familiar with this work when he first set out to develop the Transistor. Gutta Percha 10:12, 13 June 2007 (UTC)
Can somebody familiar with classic sets and recent experimentation comment on the range of frequencies/wavelengths which this type of receiver is effective with? I note elsewhere reference to around 300m and there's an old story (possibly apocryphal) of picking up 2LO [350m] with a coil of wire wrapped around your hand and a bit of coal :-)
Noting that Russia has just booted out the BBC there could be a revival of interest in simple receivers as an alternative to Internet-distributed news which is too easy to monitor or block. MarkMLl 10:39, 18 August 2007 (UTC)
One item I'd like to see addressed is the future (or end?) or crystal radio. As you may or may not know, in the USA, TV broadcasts are being FORCED! to broadcast digitally. Soon they will shut down the analog broadcast transmitters. 2009 is current target date.
Well, radio in the US and I am sure various parts of the world is showing a voluntary trend in the same direction. I hear FM stations, and yes, AM stations bragging they they now, or will be broadcasting digitally. FM claims CD quality sound, AM claims current FM quality sound from an AM digital format. New digital receivers are slowly making their way onto the market.
I don't think anyone is going to come up with a crystal digital receiver as the radio industry evolves. —Preceding unsigned comment added by Bth8446 ( talk • contribs) 16:02, 9 October 2007 (UTC)
Loading the antenna to the tuned circuit will make the RF resistance of the tuned circuit become the load, leaving too little power for the detector.
The antenna is not up to 72 ohms in resistance but far beyond.
Antenna reactance is not due to antenna capacity.
Earphone impedance should properly load detector, not highest possible. John ( talk) 23:51, 18 November 2007 (UTC)
This article has drifted far from crystal radio. The 20' & 30's section contains almost nothing about crystal radio. Other sections contain amplifier discussions and other unrelated information. These are interesting but are misplaced here. This material should be removed or moved to other articles. John ( talk) 02:31, 9 January 2008 (UTC)
"Then it uses a crystal detector to convert this radio wave electricity back to sound electricity." C'mon! 131.203.76.50 ( talk) 08:01, 16 April 2008 (UTC)
C'mon yourself. I strongly disagree, this is an encyclopedia for everybody. As a teacher of young readers, I commend efforts to include easily understandable material. We need more considerate articles. —Preceding unsigned comment added by 64.203.52.78 ( talk) 01:55, 24 May 2008 (UTC)
This is unsourced, and while interesting (if true), at present it's tangential to the topic. Perhaps it could be folded into Loudspeaker. 69.22.250.169 ( talk) 22:00, 29 January 2009 (UTC)
I'll bet that non of the people writing this article can explain why the radio can drive a headphone with only radiowaves... There simply is not enough power obtainable and the density is not enough, but researching this fact would be regarded pseudoscience. Ignorance makes the world a sad place, hopefully things will one day change... -- Nabo0o ( talk) 22:15, 11 June 2009 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
Will add a How-to section in the next few days. — Preceding unsigned comment added by Robertkeller ( talk • contribs) 06:00, 23 May 2003
It appears awkward to call this article Crystal Radio Receiver instead of the normal term of reference of Crystal Radio. I propose we move it to Crystal Radio and redirect Crystal Radio Receiver to it just in case anyone ever searches for the "Receiver" version.
John 15:22, 17 November 2006 (UTC)
The lead section is confusing, especially to laymen, I would like to omit jargon like "LC". Many simple crystal radios do not even use variable capacitors for tuning. Crystal radios use a variety of circuits and to present one circuit as defining could be misleading; the lead section should be more generic and inclusive of all that is crystal radio. It is also somewhat wrong in presenting "LC" tuning as the simpliest because inductor-only tuning is simplier than the "LC" tuning. If no one objects I plan to offer an improved, simplier, jargon-free more technically accurate, and more aware lead section wording. -DONE
John 06:14, 12 November 2006 (UTC)
That is a beautifully built artistic radio by VE6AB but in my opinion it is not as representative of crystal radio as an old one. Also, I am concerned that it is a bit commercial because it is offered for sale too. I propose to substitute a photo of a simple-minded, strictly functional old one-slider radio with an open cat whisker detector if I can find one.
John 15:19, 17 November 2006 (UTC)
Why is this awkwardly called Crystal Radio Receiver instead of the normal term of reference of Crystal Radio? I propose we move it to Crystal Radio and redirect Crystal Radio Receiver to it just in case anyone ever searches for the "Receiver" version.
John 15:22, 17 November 2006 (UTC)
Added a simple-minded explanation of how it works. Although I have posted a similar explanation elsewhere, I am the original author and I have the right to post it here and hereby declare that I release all copywright to it.
John 15:58, 17 November 2006 (UTC)
The page referenced by "Crystal Connections" is closed. We could remove it, or leave it in until web rot gives us a 404 not found.
The capacitor should be BEFORE the detector so that it forms a resonant (tank) circuit with the coil. The circuit diagram shows the capacitor after the detector: I'm sure this is wrong.
The design shown is correct! It is the classic "Fox hole" radio. The coil tunes using a slider connection and resonates against the capacitance of the antenna. This design was used because Variable Caps were not available to the builders (eg soldiers in trenches).
To put it another way, the capacitance of a long wire antena is quite large. This capacitance will swamp a normal tuned circuit and will prevent the tuning cap covering the band. At the very least the antenna needs to be tapped well down the coil or coupled in via a small value cap in series. The solution to all this was to delete the tuning cap, and instead adjust the number of turns in the coil (as shown correctly in the diagram).
BTW, the small cap shown is to bypass the RF after the detector. It is not really necessary.
The capacitor symbol is wrong (should have only two bars), but again, it attempts to show a "homemade" cap (perhaps made from layers of tinfoil from a bubblegum wrapper).
The mention of "ultra-thin litz wire inductors" is clumsy. It should be something like "many thin strands". Also Litz is NOT a new idea. It is very old.
The reference to the Pixie-2 is wrong. It's receiver is NOT a crystal set, it is a "Direct Conversion" set using an "Active Mixer".
The reference also seems to confuse Crystal Oscillators with Crystal detectors. These are two very different things.
This section seems to lack focus. Is the title of this section appropriate? It does not seem to address how to construct a 'crystal radio'. Is it intended to address the components that make it up? How they are connected? How it works or what? I think it would be helpful to figure out what this section is doing, do it and name it appropriately.
John 15:33, 17 November 2006 (UTC)
Not sure what the Construction section is doing but it has a number of problems: It introduces the concept of the simplest radio yet fails to use the simplest circuit, (which should be a coil without the tuning capacitor across it.) If someone actually builds this for the Broadcast Band, it will not tune the whole band because of the fixed antenna capacitance across the variable capacitor. Some mineral detectors are not crystals, like Lead Peroxide. Cadmium sulphide is not a reasonably good detector. The detector does not need to be (and not even typically) mounted in a brass cup (it is typically potted in Woods metal.) The cost of the antenna wire is off topic. The “…provides audio output in proportion to signal strength of signal …” is misleading in 2 ways. The “passive” and “no amplification” is redundant. The statement about “no way to control volume” is not necessarily factual. The paragraph about detection efficiency is rambling.
Anyone think we should keep this section?
John 05:08, 19 April 2007 (UTC)
Never mind that the circuit was correct, especially for a very early set. It was also the circuit of the famous Boy Scouts "slider coil" radio.
Have a look at the photo at the top right of the page. Can you see a tuning capacitor? For "clarity" you should remove that photo as well.
And by the way, it isn't a photo of a "modern set", its a re-creation of a very old set, from before the days when tuning capacitors were readily available.
This diagram?
What is confusing about it?
69.76.192.205 20:06, 24 December 2006 (UTC)
Answer to 69.76.192.205 question: what is confusing about the above diagram: Except for antenna and ground, all of the schematic symbols are non-standard, they are made up in such a way that they are not symbolic enough of the parts to wikify. These are not even antique versions of the symbols. Why not use standard symbols so all can understand? John 05:23, 19 April 2007 (UTC)
really they are all easy to understand. Capacitor ... antenna ... crystal rectifier ... headphones ... and the ground ...
J. D. Redding
02:57, 11 May 2007 (UTC)
Oh yea .. forgot to say ... thereis a rheostat coil there too ... J. D. Redding
Reply to J. D. Redding. Why use non-standard symbols? We don't need to make up symbols; it demonstrates lack of knowledge and cannot be researched (except for the antenna symbol.) We should not be introducing readers to incorrect symbols. This should be changed to a wiring pictorial or a valid schematic. Besides being out of place and unreferenced, there are technical problems with this diagram. The antenna and detector should be connected to the same point on the coil, or in a more complex circuit the detector connection separately adjustable. The capacitor is for VLF use only, and invites confusion with use as a tuning capacitor. Does it have enough value to retain? Can we fix and reference it or delete it? John 20:38, 15 May 2007 (UTC)
Technical problems with this diagram? What? This is one of the many different types of crystal radio circuits (not recognizing this is something that demonstrates a lack of knowledge about crystal radios). The circuit works too ... because this is the one I built and received sound on. No need to "fix" something that is not broken ...
This is symbols that are used in various crystal radio diagrams. Have you looked at alot of crystal radio diagrams from the 1920s up to now? These symbols have been used ... and can be used. Does not have to be a certain "wiring pictorial" or a certain type of schematic. Do you wanna change the G. W. Pickard picture because he isn't using "valid schematic". J. D. Redding 21:59, 17 May 2007 (UTC)
It has been suggested that crystal radios may still be in use by spies. This may be because crystal sets have no local oscillator so a counter-espionage organisation cannot determine that any receiver is being used by picking up the local oscillator frequency. This is a bit silly since various categories of receivers have no oscillators (e.g. TRF, Regen) and their much higher performance would be greatly prefered over a crystal set. by -- Light current 00:34, 8 September 2006 (UTC)
The following section has been twice removed from the article, however the reasons of removing seem not convincible for the contributor: The diode detector is not effective, as for weak signals (that must be rectified) the forward and reverse conductivity of the diode differs much less than it would differ for the stronger current. For the signal lever is between 20 - 100 mV, the transmission coefficient of the diode detector varies from 0.12 till as low as 0.01 [1]. The alternative methods of detection using transistors are also known. In the simpliest case, the base and emitter of the pnp bipolar transistor are connected together, and to the radio signal source. The detected radio signal is taken from collector. The transistor, connected this way can be up till 6 times more effective than diode.
Radio was the leading amateur journal in the Soviet Union and should count as a reliable source. Also, from the characteristic of the semiconductor diode in Wikipedia it is also self evident that forward and reverse conductivity does not differ much for the weak signals. Audriusa 15:36, 27 January 2007 (UTC)
It is true that a diode is an inefficient detector for weak signals (it operates in the Square Law mode). However the connection as described simply does not work. Shorting the base and emitter of a transistor produces a normal diode at the collector junction. Gutta Percha
I removed the above referenced part one of those times mostly because it was hard to understand because of grammatical and technical problems, which were subsequently improved. It is still a little flaky, however, wouldn't you agree a B-E junction of some transistors have a very sharp (non-square law) avalanche in reverse bias (ie. needs a battery!) mode, which can sometimes be more efficient than unbiased detection. John 06:47, 27 February 2007 (UTC)
No. You describe an Avalanche diode, which is an active device. The radio is then no longer a Crystal set. Gutta Percha 10:04, 13 June 2007 (UTC)
The Crystadyne section is facinating, but not squarely on topic for this article. It is an early discovery of solid state amplification instead of passive crystal radio. I plan to remove it and create a new stand alone article with it if there are no objections. John 22:02, 10 May 2007 (UTC)
Good Idea. In the early days there were many references to amplification using crystal detectors with multiple "catswhiskers" and bias. It is clear that Schottky was familiar with this work when he first set out to develop the Transistor. Gutta Percha 10:12, 13 June 2007 (UTC)
Can somebody familiar with classic sets and recent experimentation comment on the range of frequencies/wavelengths which this type of receiver is effective with? I note elsewhere reference to around 300m and there's an old story (possibly apocryphal) of picking up 2LO [350m] with a coil of wire wrapped around your hand and a bit of coal :-)
Noting that Russia has just booted out the BBC there could be a revival of interest in simple receivers as an alternative to Internet-distributed news which is too easy to monitor or block. MarkMLl 10:39, 18 August 2007 (UTC)
One item I'd like to see addressed is the future (or end?) or crystal radio. As you may or may not know, in the USA, TV broadcasts are being FORCED! to broadcast digitally. Soon they will shut down the analog broadcast transmitters. 2009 is current target date.
Well, radio in the US and I am sure various parts of the world is showing a voluntary trend in the same direction. I hear FM stations, and yes, AM stations bragging they they now, or will be broadcasting digitally. FM claims CD quality sound, AM claims current FM quality sound from an AM digital format. New digital receivers are slowly making their way onto the market.
I don't think anyone is going to come up with a crystal digital receiver as the radio industry evolves. —Preceding unsigned comment added by Bth8446 ( talk • contribs) 16:02, 9 October 2007 (UTC)
Loading the antenna to the tuned circuit will make the RF resistance of the tuned circuit become the load, leaving too little power for the detector.
The antenna is not up to 72 ohms in resistance but far beyond.
Antenna reactance is not due to antenna capacity.
Earphone impedance should properly load detector, not highest possible. John ( talk) 23:51, 18 November 2007 (UTC)
This article has drifted far from crystal radio. The 20' & 30's section contains almost nothing about crystal radio. Other sections contain amplifier discussions and other unrelated information. These are interesting but are misplaced here. This material should be removed or moved to other articles. John ( talk) 02:31, 9 January 2008 (UTC)
"Then it uses a crystal detector to convert this radio wave electricity back to sound electricity." C'mon! 131.203.76.50 ( talk) 08:01, 16 April 2008 (UTC)
C'mon yourself. I strongly disagree, this is an encyclopedia for everybody. As a teacher of young readers, I commend efforts to include easily understandable material. We need more considerate articles. —Preceding unsigned comment added by 64.203.52.78 ( talk) 01:55, 24 May 2008 (UTC)
This is unsourced, and while interesting (if true), at present it's tangential to the topic. Perhaps it could be folded into Loudspeaker. 69.22.250.169 ( talk) 22:00, 29 January 2009 (UTC)
I'll bet that non of the people writing this article can explain why the radio can drive a headphone with only radiowaves... There simply is not enough power obtainable and the density is not enough, but researching this fact would be regarded pseudoscience. Ignorance makes the world a sad place, hopefully things will one day change... -- Nabo0o ( talk) 22:15, 11 June 2009 (UTC)