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The list of disadvantages is suspect.
Terman 1943 p 658 characterizes the TRF's disadvantages as "poor selectivity and low sensitivity in proportion to the number of tubes employed. They are accordingly practically obsolete."
For a variable tuned receiver, a primary disadvantage would be the trouble with synchronous tuning.
Also, wide ranges of frequencies require bandswitching. Old variable capacitors might be 40 to 360 pF -- a 9:1 cap ratio that only gives (ignoring pads and strays) a 3:1 frequency ratio. (AM superhets would do 540 kHz to 1600 kHz.)
For the given list of disadvantages:
Glrx ( talk) 04:03, 14 March 2011 (UTC)
The article says, Inside, [...] will be a series of large coils. These will sometimes be tilted slightly to reduce interaction between their magnetic fields. But, the picture that follows shows three coils, at right angles to each other (which makes sense). Perhaps the wording, sometimes be tilted slightly is too timid? -- RoySmith (talk) 14:55, 18 November 2012 (UTC)
I would like to delete the following paragraph, but hesitate to do so as I don't want to appear too aggressive:
I feel that there is a problem in the distinction between "TRF" and "regenerative" receivers, and also in the usage of "regenerative detector": this problem also exists in the Wiki "Regenerative Circuit" page. In the UK, reaction (also termed "regeneration") was universally applied to TRF receivers up to the early 1930s - that is, throughout their period of vogue. Reaction could be applied to any of the RF stages, or to several, but was most often applied to the detector stage only. Its purpose was to increase gain, and narrow the bandwidth, both of which it does spectacularly well. These receivers were not called "regenerative receivers", and the detector stage with reaction was not called a "regenerative detector" - it was called a leaky grid detector with reaction. When reaction (or regeneration) is applied in this way, it is not intended that the amplifier should oscillate, though if badly adjusted it could do so. If the set were made to oscillate, it ceased to function correctly, producing howls and whistles, so it should not be understood that this type of receiver routinely oscillated continuously; oscillation was an accident that sometimes happened during tuning and adjustment. In contrast to this, there exists a class of receiver known as a "regenerative receiver" which employs a "regenerative detector". This type of receiver is used for reception of SSB and CW signals (but not AM), and is also called an "autodyne". The circuit is almost identical to a TRF set with reaction, but differs in use in that sufficient reaction is applied that the detector stage oscillates continuously. This continuous oscillation provides the carrier which is present in AM transmissions, but is absent in SSB & CW transmissions. The oscillating detector acts as a heterodyne detector, and receivers of this type can also be classified as "direct conversion" receivers, though the term "autodyne" is preferable. It seems to me that the article, as it stands, conflates these two distinct types of receiver. It interests me that in the US (and perhaps elsewhere) reaction was not usually applied to TRF receivers, and I would like to know why. I suspect that it might have been to do with patent restrictions which for some reason did not apply in the UK. The description given in the article seems to be restricted to the types most common in the US, and the author seems not to be aware of the form that TRF receivers took in other lands. G4oep ( talk) 20:04, 23 January 2015 (UTC)
Thanks for the comments... its all very interesting. What is on my mind is the terminology, and clarification of the different types of receivers. In the UK, 1920s receivers which we would now classify as TRF always had reaction fitted (in the UK). But I am not aware that they were termed regenerative receivers. In the amateur radio fraternity "regenerative receivers" always refers to autodyne receivers, which operate on a different principle. These have circuits which are often indistinguishable from single-valve TRF sets with reaction & grid-leak detectors. But in use, the reaction control is set so that the valve oscillates. The oscillation provides the missing "carrier" which is needed for detection of SSB & CW signals. This type of receiver is an autodyne, and could also be classed as a direct conversion receiver. Because the valve always oscillates, the risk of radiating an unwanted signal which can cause interference is constantly present. This is unlike the case with an AM TRF with reaction, where, if properly adjusted there will be no radiation. So I wonder whether there is consensus that "regenerative receiver" should be reserved for the autodyne type; if there is, then the paragraph I refer to should be changed.
I would classify receivers on the basis of how they achieve selectivity: 1) TRF by filtering at the frequency of the received signal; I would make this a definition of a TRF receiver. TRFs include crystal sets and also typical 1920s sets with reaction. 2) superhets; filtering at a fixed intermediate frequency 3) direct conversion; filtering at af (includes autodynes).
Then I would classify them according to the type of detector: For AM: anode bend, grid leak, discreet diode, homodyne, etc For SSB & CW: all the different kinds we know about (endless variety), autodyne FM: ratio, quadrature, etc
Thus a crystal set would be a TRF with diode detector. A "regenerative" would be a direct conversion RX with autodyne detector, or maybe just an autodyne receiver (autodyne & regenerative receivers are different names for the same thing in my mind). A 1920s type would be TRF with grid-leak detector; if it had reaction that would not change the classification, but you could add that detail in the description. A typical FM rig would be a superhet with quadrature detector. Super-regenerative receivers are TRF sets with reaction. The reaction is set so that if left to itself, the signal would gradually increase in magnitude and the set would oscillate, but the receiver is periodically interrupted at a super-sonic frequency so that self-sustained oscillations are never actually able to occur. Would readers like me to get my hands on this article and sort it out along these lines ? G4oep ( talk) 16:18, 24 January 2015 (UTC)
I agree, the definition "...all the bandpass filtering... is done at the RF frequency" is too broad. Crystal radios and reflex receivers would also come under that def. and possibly regenerative receivers depending on your point of view. That was my addition; I don't know how that slipped in. Thanks for catching it, Grlx.
I have some reservations about the other definitions. A lot of sources [2], [3], (Terman 1943, p. 658) define a TRF receiver as: "one or more tuned RF stages, a detector stage, followed by one or more audio amplifier stages". This def bothers me historically, because I think I have read that early TRF receivers without audio stages were called TRFs. Before broadcasting began in 1920, radio was a solitary hobby and there were few loudspeakers marketed, so most radio receivers were designed to be listened to with earphones, which could be driven by the detector and didn't need an audio amp stage. I think the term TRF was even applied to the first one-tube nonregenerative receivers like De Forest made, where the detector provided all the gain. I think back then "tuned radio frequency" was just a name that was used to distinguish a receiver from a regenerative receiver. Of course I need to find these references. What do you think? -- Chetvorno TALK 03:14, 27 July 2015 (UTC)
Hello Glrx ( talk · contribs). You were concerned about the reliability of the statement regarding the use tuned radio frequency receivers versus heterodyne receivers during WWII. Here is the more information confirmed by another reference, an article from the August 1980 edition of CQ Magazine, pp. 21-22.
New reference: (deleted link)
“You are probably surprised that the Germans used t.r.f. sets. But they certainly knew how to make them in superior form. A great advantage of the straight set is that spurious responses are non-existent, even in the presence of extremely strong signals as in shipboard use, where several transmitters may be active at the same time receivers are operated.
"Another advantage from a military point of view is that the t.r.f. set does not use oscillators and so the chance of location by the enemy using a direction finder on spurious radiation of the set is negligible. This article could only be prepared thanks to the assistance of PA0AOB. Not only did he make the receivers available for photography, he also gave the author the opportunity of using some of the sets in his own shack for a considerable period of time.
"The fact that PA0AOB could provided the original technical manuals, or exact replicas of them, was also of great help in the preparation of this article.”
How about we put the original paragraph back in, and improve it with this latest material? Regards, Desertroad ( talk) 16:10, 22 August 2016 (UTC)
Why is a CMOS book the reference for neutralization in vacuum tubes? I don't have the book, but I would suspect that there should be more historical references around. Gah4 ( talk) 13:33, 21 March 2020 (UTC)
This is the
talk page for discussing improvements to the
Tuned radio frequency receiver article. This is not a forum for general discussion of the article's subject. |
Article policies
|
Find sources: Google ( books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL |
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||||||||||
|
The list of disadvantages is suspect.
Terman 1943 p 658 characterizes the TRF's disadvantages as "poor selectivity and low sensitivity in proportion to the number of tubes employed. They are accordingly practically obsolete."
For a variable tuned receiver, a primary disadvantage would be the trouble with synchronous tuning.
Also, wide ranges of frequencies require bandswitching. Old variable capacitors might be 40 to 360 pF -- a 9:1 cap ratio that only gives (ignoring pads and strays) a 3:1 frequency ratio. (AM superhets would do 540 kHz to 1600 kHz.)
For the given list of disadvantages:
Glrx ( talk) 04:03, 14 March 2011 (UTC)
The article says, Inside, [...] will be a series of large coils. These will sometimes be tilted slightly to reduce interaction between their magnetic fields. But, the picture that follows shows three coils, at right angles to each other (which makes sense). Perhaps the wording, sometimes be tilted slightly is too timid? -- RoySmith (talk) 14:55, 18 November 2012 (UTC)
I would like to delete the following paragraph, but hesitate to do so as I don't want to appear too aggressive:
I feel that there is a problem in the distinction between "TRF" and "regenerative" receivers, and also in the usage of "regenerative detector": this problem also exists in the Wiki "Regenerative Circuit" page. In the UK, reaction (also termed "regeneration") was universally applied to TRF receivers up to the early 1930s - that is, throughout their period of vogue. Reaction could be applied to any of the RF stages, or to several, but was most often applied to the detector stage only. Its purpose was to increase gain, and narrow the bandwidth, both of which it does spectacularly well. These receivers were not called "regenerative receivers", and the detector stage with reaction was not called a "regenerative detector" - it was called a leaky grid detector with reaction. When reaction (or regeneration) is applied in this way, it is not intended that the amplifier should oscillate, though if badly adjusted it could do so. If the set were made to oscillate, it ceased to function correctly, producing howls and whistles, so it should not be understood that this type of receiver routinely oscillated continuously; oscillation was an accident that sometimes happened during tuning and adjustment. In contrast to this, there exists a class of receiver known as a "regenerative receiver" which employs a "regenerative detector". This type of receiver is used for reception of SSB and CW signals (but not AM), and is also called an "autodyne". The circuit is almost identical to a TRF set with reaction, but differs in use in that sufficient reaction is applied that the detector stage oscillates continuously. This continuous oscillation provides the carrier which is present in AM transmissions, but is absent in SSB & CW transmissions. The oscillating detector acts as a heterodyne detector, and receivers of this type can also be classified as "direct conversion" receivers, though the term "autodyne" is preferable. It seems to me that the article, as it stands, conflates these two distinct types of receiver. It interests me that in the US (and perhaps elsewhere) reaction was not usually applied to TRF receivers, and I would like to know why. I suspect that it might have been to do with patent restrictions which for some reason did not apply in the UK. The description given in the article seems to be restricted to the types most common in the US, and the author seems not to be aware of the form that TRF receivers took in other lands. G4oep ( talk) 20:04, 23 January 2015 (UTC)
Thanks for the comments... its all very interesting. What is on my mind is the terminology, and clarification of the different types of receivers. In the UK, 1920s receivers which we would now classify as TRF always had reaction fitted (in the UK). But I am not aware that they were termed regenerative receivers. In the amateur radio fraternity "regenerative receivers" always refers to autodyne receivers, which operate on a different principle. These have circuits which are often indistinguishable from single-valve TRF sets with reaction & grid-leak detectors. But in use, the reaction control is set so that the valve oscillates. The oscillation provides the missing "carrier" which is needed for detection of SSB & CW signals. This type of receiver is an autodyne, and could also be classed as a direct conversion receiver. Because the valve always oscillates, the risk of radiating an unwanted signal which can cause interference is constantly present. This is unlike the case with an AM TRF with reaction, where, if properly adjusted there will be no radiation. So I wonder whether there is consensus that "regenerative receiver" should be reserved for the autodyne type; if there is, then the paragraph I refer to should be changed.
I would classify receivers on the basis of how they achieve selectivity: 1) TRF by filtering at the frequency of the received signal; I would make this a definition of a TRF receiver. TRFs include crystal sets and also typical 1920s sets with reaction. 2) superhets; filtering at a fixed intermediate frequency 3) direct conversion; filtering at af (includes autodynes).
Then I would classify them according to the type of detector: For AM: anode bend, grid leak, discreet diode, homodyne, etc For SSB & CW: all the different kinds we know about (endless variety), autodyne FM: ratio, quadrature, etc
Thus a crystal set would be a TRF with diode detector. A "regenerative" would be a direct conversion RX with autodyne detector, or maybe just an autodyne receiver (autodyne & regenerative receivers are different names for the same thing in my mind). A 1920s type would be TRF with grid-leak detector; if it had reaction that would not change the classification, but you could add that detail in the description. A typical FM rig would be a superhet with quadrature detector. Super-regenerative receivers are TRF sets with reaction. The reaction is set so that if left to itself, the signal would gradually increase in magnitude and the set would oscillate, but the receiver is periodically interrupted at a super-sonic frequency so that self-sustained oscillations are never actually able to occur. Would readers like me to get my hands on this article and sort it out along these lines ? G4oep ( talk) 16:18, 24 January 2015 (UTC)
I agree, the definition "...all the bandpass filtering... is done at the RF frequency" is too broad. Crystal radios and reflex receivers would also come under that def. and possibly regenerative receivers depending on your point of view. That was my addition; I don't know how that slipped in. Thanks for catching it, Grlx.
I have some reservations about the other definitions. A lot of sources [2], [3], (Terman 1943, p. 658) define a TRF receiver as: "one or more tuned RF stages, a detector stage, followed by one or more audio amplifier stages". This def bothers me historically, because I think I have read that early TRF receivers without audio stages were called TRFs. Before broadcasting began in 1920, radio was a solitary hobby and there were few loudspeakers marketed, so most radio receivers were designed to be listened to with earphones, which could be driven by the detector and didn't need an audio amp stage. I think the term TRF was even applied to the first one-tube nonregenerative receivers like De Forest made, where the detector provided all the gain. I think back then "tuned radio frequency" was just a name that was used to distinguish a receiver from a regenerative receiver. Of course I need to find these references. What do you think? -- Chetvorno TALK 03:14, 27 July 2015 (UTC)
Hello Glrx ( talk · contribs). You were concerned about the reliability of the statement regarding the use tuned radio frequency receivers versus heterodyne receivers during WWII. Here is the more information confirmed by another reference, an article from the August 1980 edition of CQ Magazine, pp. 21-22.
New reference: (deleted link)
“You are probably surprised that the Germans used t.r.f. sets. But they certainly knew how to make them in superior form. A great advantage of the straight set is that spurious responses are non-existent, even in the presence of extremely strong signals as in shipboard use, where several transmitters may be active at the same time receivers are operated.
"Another advantage from a military point of view is that the t.r.f. set does not use oscillators and so the chance of location by the enemy using a direction finder on spurious radiation of the set is negligible. This article could only be prepared thanks to the assistance of PA0AOB. Not only did he make the receivers available for photography, he also gave the author the opportunity of using some of the sets in his own shack for a considerable period of time.
"The fact that PA0AOB could provided the original technical manuals, or exact replicas of them, was also of great help in the preparation of this article.”
How about we put the original paragraph back in, and improve it with this latest material? Regards, Desertroad ( talk) 16:10, 22 August 2016 (UTC)
Why is a CMOS book the reference for neutralization in vacuum tubes? I don't have the book, but I would suspect that there should be more historical references around. Gah4 ( talk) 13:33, 21 March 2020 (UTC)