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I.F.Transformers?
In an old-style valve (tube) communications receiver circuit which utilises
two I.F. stages and uses three I.F. transformers, can someone explain why the last I.F. transformer (which feeds the diode detector stage) need to differ in some way to the other two? Any help would be greatly appreciated. Theo |
I.F.Transformers?
The first two feed grids that have a higher impedance than a diode that
is fed by the third. -- 73 Hank WD5JFR "Theo" wrote in message ... In an old-style valve (tube) communications receiver circuit which utilises two I.F. stages and uses three I.F. transformers, can someone explain why the last I.F. transformer (which feeds the diode detector stage) need to differ in some way to the other two? Any help would be greatly appreciated. Theo |
I.F.Transformers?
"Henry Kolesnik" wrote in message ... The first two feed grids that have a higher impedance than a diode that is fed by the third. Thanks Hank, Does this mean that the windings of this third I.F. transformer need to be different in some way than the previous two, and if so, by how much? Theo |
I.F.Transformers?
Theo
The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. -- Thanks & 73 Hank WD5JFR "Theo" wrote in message ... "Henry Kolesnik" wrote in message ... The first two feed grids that have a higher impedance than a diode that is fed by the third. Thanks Hank, Does this mean that the windings of this third I.F. transformer need to be different in some way than the previous two, and if so, by how much? Theo |
I.F.Transformers?
Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. The over 1000-page one is the Fourth Edition, which is the most expensive on the used market, and the one which has the most hi-fi information in it. The discussion of IF strip design is also in the smaller and much less expensive Third Edition. Some people like the third edition because it has some information on transformer design which was not carried into the fourth. A copy of the fourth edition is available online he http://geek.scorpiorising.ca/RDH4.html --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
I.F.Transformers?
"Scott Dorsey" wrote in message
... Henry Kolesnik wrote: The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. The over 1000-page one is the Fourth Edition, which is the most expensive on the used market, and the one which has the most hi-fi information in it. The discussion of IF strip design is also in the smaller and much less expensive Third Edition. Some people like the third edition because it has some information on transformer design which was not carried into the fourth. A copy of the fourth edition is available online he http://geek.scorpiorising.ca/RDH4.html --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." It would certainly help to see the schematic before jumping to conclusions. There are many designs out there between American 5 and FT1000D, and you don't specify. |
I.F.Transformers?
Over the years I've gone thru several 4th editions but have never seen
any of its predecessors. I'll have to watchout for some. "Scott Dorsey" wrote in message ... Henry Kolesnik wrote: The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. The over 1000-page one is the Fourth Edition, which is the most expensive on the used market, and the one which has the most hi-fi information in it. The discussion of IF strip design is also in the smaller and much less expensive Third Edition. Some people like the third edition because it has some information on transformer design which was not carried into the fourth. A copy of the fourth edition is available online he http://geek.scorpiorising.ca/RDH4.html --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
I.F.Transformers?
Hey JB
I assumed since the query was in this group it wouldn't be a FT-1000 and not an AA5 because it has only one IF. It would be nice to know what radio but anxious people making queries and get carried away and I'm one.. Hank "JB" wrote in message ... "Scott Dorsey" wrote in message ... Henry Kolesnik wrote: The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. The over 1000-page one is the Fourth Edition, which is the most expensive on the used market, and the one which has the most hi-fi information in it. The discussion of IF strip design is also in the smaller and much less expensive Third Edition. Some people like the third edition because it has some information on transformer design which was not carried into the fourth. A copy of the fourth edition is available online he http://geek.scorpiorising.ca/RDH4.html --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." It would certainly help to see the schematic before jumping to conclusions. There are many designs out there between American 5 and FT1000D, and you don't specify. |
I.F.Transformers?
Henry Kolesnik wrote:
Over the years I've gone thru several 4th editions but have never seen any of its predecessors. I'll have to watchout for some. I see the second and third editions at hamfests a lot. They are often black and less than half the width of the 4th edition so you might not see it unless you're looking for it. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
I.F.Transformers?
"Scott Dorsey" wrote in message ... Henry Kolesnik wrote: The secondary of the IF xfmrm feeding the diode will have a different winding than the first two. My transformer theory is not up to snuff, I'm 68 and if I recall correctly a diode has a much lower input impedance that has to be matched so I'm guessing it will have less turns. Remember that a transformer reflects the impedance back. You may want to get a copy of The Radiotron Designers Handbook by Langford, it covers just about anything you would want to know about tube radios, over 1000 pages. The over 1000-page one is the Fourth Edition, which is the most expensive on the used market, and the one which has the most hi-fi information in it. The discussion of IF strip design is also in the smaller and much less expensive Third Edition. Some people like the third edition because it has some information on transformer design which was not carried into the fourth. A copy of the fourth edition is available online he http://geek.scorpiorising.ca/RDH4.html --scott The forth edition is available in PDF form from Pete Milette's site: http://www.pmillett.com/ Along with many other classic books including K.R.Sturley's two volume book on radio receiver design. The organization of the site is a bit confusing so a bit of poking around in needed to find everything. The quality of his scans is excellent but the files are _very_ large and really require a high speed connection to be practical. I also recommend the 4th edition of the Radiotron, I think I have two, the one I bought new fell apart from use (rebound it). The 3rd edition, which is much smaller, also has a lot of useful information in it. I agree with the statements made about the final IF transformer but not all detectors offer low impedance to the transformer although this is true of straight diode detectors. Both of the above books have thorough discussions of AM detectors and their relative merits. -- Richard Knoppow Los Angeles WB6KBL |
I.F.Transformers?
Richard Knoppow wrote:
"Scott Dorsey" wrote in message ... Henry Kolesnik wrote: Over the years I've gone thru several 4th editions but have never seen any of its predecessors. I'll have to watchout for some. I see the second and third editions at hamfests a lot. They are often black and less than half the width of the 4th edition so you might not see it unless you're looking for it. --scott I suspect people with the 4th edition just never sell them. What I would love to find one day is the original Australian edition of the 4th. The American (RCA) edition was produced by photo-offset and some of the charts leave something to be desired. -- Richard Knoppow Los Angeles WB6KBL Guess I'm lucky.... I have an RCA version and the one from ... well, let's see. It says typeset in Australia and published by Billings and Sons Ltd. London. Is that the good one? de K3HVG -- Posted Via Newsfeeds.com Premium Usenet Newsgroup Service ---------------------------------------------------------- http://www.Newsfeeds.com |
I.F.Transformers?
k3hvg wrote:
Richard Knoppow wrote: "Scott Dorsey" wrote in message ... Henry Kolesnik wrote: Over the years I've gone thru several 4th editions but have never seen any of its predecessors. I'll have to watchout for some. I see the second and third editions at hamfests a lot. They are often black and less than half the width of the 4th edition so you might not see it unless you're looking for it. --scott I suspect people with the 4th edition just never sell them. What I would love to find one day is the original Australian edition of the 4th. The American (RCA) edition was produced by photo-offset and some of the charts leave something to be desired. -- Richard Knoppow Los Angeles WB6KBL Guess I'm lucky.... I have an RCA version and the one from ... well, let's see. It says typeset in Australia and published by Billings and Sons Ltd. London. Is that the good one? de K3HVG Nope... that wasn't correct. It says Published by Amalgamated Wireless Valve Co. of Australia but printed and bound by the folks at Billings (London) and dated 1954. I guess that's how they did it? -- Posted Via Newsfeeds.com Premium Usenet Newsgroup Service ---------------------------------------------------------- http://www.Newsfeeds.com |
I.F.Transformers?
The particular receiver Theo was asking about uses a 6SQ7 dual-diode, triode
as a diode detector. I found it in the 1950 Radio Amateur's Handbook. The schematic may be a bit misleading, though, since it shows a schematic of the diode transformer that is the same as an if transformer - which is tuned primary and tuned secondary - with the full winding on the secondary used for the diode. I found this concise statement in the 1942 Editors and Engineers Radio Handbook "Diodes load the tuned circuit to which they are connected, however, and thus reduce selectivity slightly. Special i.f. transformers are used for the purpose of providing a low-impedance input circuit to the diode detector." If I were winding the i.f. transformer, I would use a hi-q secondary and tap down for the diode, so that selectivity is maintained, while properly matching the diode input impedance. That may be how the transformer is connected, although it does not show that on the schematic. Colin K7FM |
I.F.Transformers?
"k3hvg" wrote in message ... k3hvg wrote: Richard Knoppow wrote: "Scott Dorsey" wrote in message ... Henry Kolesnik wrote: Over the years I've gone thru several 4th editions but have never seen any of its predecessors. I'll have to watchout for some. I see the second and third editions at hamfests a lot. They are often black and less than half the width of the 4th edition so you might not see it unless you're looking for it. --scott I suspect people with the 4th edition just never sell them. What I would love to find one day is the original Australian edition of the 4th. The American (RCA) edition was produced by photo-offset and some of the charts leave something to be desired. -- Richard Knoppow Los Angeles WB6KBL Guess I'm lucky.... I have an RCA version and the one from ... well, let's see. It says typeset in Australia and published by Billings and Sons Ltd. London. Is that the good one? de K3HVG Nope... that wasn't correct. It says Published by Amalgamated Wireless Valve Co. of Australia but printed and bound by the folks at Billings (London) and dated 1954. I guess that's how they did it? -- Posted Via Newsfeeds.com Premium Usenet Newsgroup Service ---------------------------------------------------------- http://www.Newsfeeds.com |
I.F.Transformers?
"k3hvg" wrote in message ... k3hvg wrote: Richard Knoppow wrote: "Scott Dorsey" wrote in message ... Henry Kolesnik wrote: Over the years I've gone thru several 4th editions but have never seen any of its predecessors. I'll have to watchout for some. I see the second and third editions at hamfests a lot. They are often black and less than half the width of the 4th edition so you might not see it unless you're looking for it. --scott I suspect people with the 4th edition just never sell them. What I would love to find one day is the original Australian edition of the 4th. The American (RCA) edition was produced by photo-offset and some of the charts leave something to be desired. -- Richard Knoppow Los Angeles WB6KBL Guess I'm lucky.... I have an RCA version and the one from ... well, let's see. It says typeset in Australia and published by Billings and Sons Ltd. London. Is that the good one? de K3HVG Nope... that wasn't correct. It says Published by Amalgamated Wireless Valve Co. of Australia but printed and bound by the folks at Billings (London) and dated 1954. I guess that's how they did it? Not sure, it might be an English edition. The title page of the RCA edition says: Published by the Wireless Press for The Amalgamated Wireless Valve Company PTY limited 47 York Street, Sydney, Australia 1953 Since the RCA edition was reproduced by photo-lithography this is likely what the Australian edition says. I take "published" to mean printed and bound. I suspect the English edition may have been reproduced by photo-lithograph in the same way as the USA/RCA edition was. In both cases it would be much cheaper to print and bind locally rather than ship complete books from Australia plus the Ausies may not have had a large enough printing facility at the time since the entire population of Oz was probably not more than ten million. The main sign of the photolighography I see is a slight clogging of some of the charts. Not a big deal. This was a magnum opus and I doubt if anything like it will ever again be published in its field. RCA, like Kodak, was an extremely good source of educational information. For instance, the tutorial on vacuum tubes in the front of nearly all of the receiving tube handbooks is excellent. We didn't appreciate this stuff when it was available. I was given the third edition of the RDH by an engineer I knew when in my early teens. When the forth edition was published I bought one immediately, I still remember doing it. It came in the proverbial plain brown wrapper which, of course, soon got lost. Its a book you can cuddle up to and read over an over. I learned a great deal from it. It also has a very exensive bibliography and many of the citations are worth looking up. K.R.Sturley's book, also available on Pete Milette's site, is also worth having. It concentrates on radio receiver design but, even though both of these books were written before solid state electronics much if both are still applicable, for instance filter design, etc. I strongly recomend poking around on Pete's site, there is a lot of valuable stuff there. -- -- Richard Knoppow Los Angeles, CA, USA |
I.F.Transformers?
Colin
I'm curious as to how you know what Rx Theo was asking about since I've not seen it mentioned? -- Thanks & 73 Hank WD5JFR "COLIN LAMB" wrote in message m... The particular receiver Theo was asking about uses a 6SQ7 dual-diode, triode as a diode detector. I found it in the 1950 Radio Amateur's Handbook. The schematic may be a bit misleading, though, since it shows a schematic of the diode transformer that is the same as an if transformer - which is tuned primary and tuned secondary - with the full winding on the secondary used for the diode. I found this concise statement in the 1942 Editors and Engineers Radio Handbook "Diodes load the tuned circuit to which they are connected, however, and thus reduce selectivity slightly. Special i.f. transformers are used for the purpose of providing a low-impedance input circuit to the diode detector." If I were winding the i.f. transformer, I would use a hi-q secondary and tap down for the diode, so that selectivity is maintained, while properly matching the diode input impedance. That may be how the transformer is connected, although it does not show that on the schematic. Colin K7FM |
I.F.Transformers?
I cheated by asking him.
Colin K7FM |
I.F.Transformers?
Colin
The diode load resistor in most of the diode detector circuits I'm familiar with have several hundred kilo ohms and I think 6SQ7 diode has a few hundred ohms so the total reflected impedance to the last IF is the pretty much the resistive load. And if my 68 yr old memory serves me right most commonly used IF transformers had an input and output part number and in some cases interstage but that may have been for TV IF. I don't recall replacing many transformers because they failed electrically but because the little ferrite core with a hex hole would crack and could no longer be turned. Many times this was because of a previous repair where a monkey not a tech, tried to tweak it and broke the core. I also worked on a one set that had the first IF transformer installed backwards at the IF mfg factory, not the TV assembly plant. That took some time to find considering the test eqpt at hand was limited to a vtvm and an audio scope. Time to stop rambling and ask if the ARRL article distinguished the IF transformers with different part numbers? -- Thanks & 73 Hank WD5JFR "COLIN LAMB" wrote in message m... The particular receiver Theo was asking about uses a 6SQ7 dual-diode, triode as a diode detector. I found it in the 1950 Radio Amateur's Handbook. The schematic may be a bit misleading, though, since it shows a schematic of the diode transformer that is the same as an if transformer - which is tuned primary and tuned secondary - with the full winding on the secondary used for the diode. I found this concise statement in the 1942 Editors and Engineers Radio Handbook "Diodes load the tuned circuit to which they are connected, however, and thus reduce selectivity slightly. Special i.f. transformers are used for the purpose of providing a low-impedance input circuit to the diode detector." If I were winding the i.f. transformer, I would use a hi-q secondary and tap down for the diode, so that selectivity is maintained, while properly matching the diode input impedance. That may be how the transformer is connected, although it does not show that on the schematic. Colin K7FM |
I.F.Transformers?
"Time to stop rambling and ask if the ARRL article distinguished the IF
transformers with different part numbers?" Yes The first and second stage transformers are designated "456 kc interstage if transformer, permeability-tuned (Millen 64456)". The third if transformer (to the diode detector) is designated "456 kc diode transformer, permeability-tuned (Millen 65454)". The schematic drawing for all three transformers are the same, but the secondary of the last transformer would be different to attain a lower impedance. 73, Colin K7FM |
I.F.Transformers?
Colin
Good on yah mate.. Now to express it another way the winding ratio of the diode transformer has to be such that when it reflects the diode and its load to the plate of the last IF, the plate circuit will see the correct impedance for the IF tube load. Transformers don't have impedance, only turns ratio to reflect back whatever impedance they see in accordance with the turns ratio. -- 73 Hank WD5JFR "COLIN LAMB" wrote in message m... "Time to stop rambling and ask if the ARRL article distinguished the IF transformers with different part numbers?" Yes The first and second stage transformers are designated "456 kc interstage if transformer, permeability-tuned (Millen 64456)". The third if transformer (to the diode detector) is designated "456 kc diode transformer, permeability-tuned (Millen 65454)". The schematic drawing for all three transformers are the same, but the secondary of the last transformer would be different to attain a lower impedance. 73, Colin K7FM |
I.F.Transformers?
Hey JB
I assumed since the query was in this group it wouldn't be a FT-1000 and not an AA5 because it has only one IF. It would be nice to know what radio but anxious people making queries and get carried away and I'm one.. Hank I hear ya! Most of these discussions leave the tracks in a hurry and wind up out in the cornfield. We don't know if a bfo or product detector or regen or filters or a converter stage involved. Everybody else seems to have thrown the book at him. |
I.F.Transformers?
"Henry Kolesnik" wrote in message ... Colin Good on yah mate.. Now to express it another way the winding ratio of the diode transformer has to be such that when it reflects the diode and its load to the plate of the last IF, the plate circuit will see the correct impedance for the IF tube load. Transformers don't have impedance, only turns ratio to reflect back whatever impedance they see in accordance with the turns ratio. Thats fine for untuned transformers, but surely in the case of these I.F. transformers that consist of mutually coupled parallel tuned circuits, this must be different? |
I.F.Transformers?
A tuned circuit is a reactive load just like an untuned circuit except
its reactance is max at the desired frequency. Any DC resistance such as the diode and it's load are undesirable as they lower Q. -- 73 Hank WD5JFR "Theo" wrote in message ... "Henry Kolesnik" wrote in message ... Colin Good on yah mate.. Now to express it another way the winding ratio of the diode transformer has to be such that when it reflects the diode and its load to the plate of the last IF, the plate circuit will see the correct impedance for the IF tube load. Transformers don't have impedance, only turns ratio to reflect back whatever impedance they see in accordance with the turns ratio. Thats fine for untuned transformers, but surely in the case of these I.F. transformers that consist of mutually coupled parallel tuned circuits, this must be different? |
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