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#1
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6 bit binary attenuator. - 6 bit attenuator.pdf
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#2
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6 bit binary attenuator. - 6 bit attenuator.pdf
John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. -- You can't have a sense of humor, if you have no sense. |
#3
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6 bit binary attenuator. - 6 bit attenuator.pdf
Michael A. Terrell Inscribed thus:
John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. Yes some toggle switches have poor isolation. I built one many years ago with slide switches. Above about 100Mhz an open switch only had about 38 - 39 Db attenuation. I think the contacts were far to close together for good performance. I now have a Rhode & Schwarz attenuator, good to at least 1Ghz. -- Best Regards: Baron. |
#4
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 12:49:59 -0600, John Fields
wrote: Math errors in first two stages. John |
#5
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 15:31:07 -0500, "Michael A. Terrell"
wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? --- Nope, it was just an exercise to prove a point on sed. --- The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. --- OK. -- JF |
#6
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 13:32:41 -0800, John Larkin
wrote: On Sat, 19 Nov 2011 12:49:59 -0600, John Fields wrote: Math errors in first two stages. --- It happens... Care to post the corrections? -- JF |
#7
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 16:10:07 -0600, John Fields
wrote: On Sat, 19 Nov 2011 13:32:41 -0800, John Larkin wrote: On Sat, 19 Nov 2011 12:49:59 -0600, John Fields wrote: Math errors in first two stages. --- It happens... Especially when you don't check your work, or even review it for reasonableness. Care to post the corrections? Lots of online calculators are available. John |
#8
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 15:31:07 -0500, "Michael A. Terrell"
wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. They probably used pi, rather than tee, stages for some good reason. John |
#9
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6 bit binary attenuator. - 6 bit attenuator.pdf
Baron wrote: Michael A. Terrell Inscribed thus: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. Yes some toggle switches have poor isolation. I built one many years ago with slide switches. Above about 100Mhz an open switch only had about 38 - 39 Db attenuation. I think the contacts were far to close together for good performance. I now have a Rhode & Schwarz attenuator, good to at least 1Ghz. I have a couple Weinschel variable attenuators that are good past 5 GHz. Microdyne used them in their early telemetry test sets & C-band signal generators. They paid over $900 each, in the '90s. Some were replaced after a couple years on the test floor, the other is in a C-band sig generator to test commercial Sat equipment. http://www.aeroflex.com/ams/weinsche...S/stepattn.pdf they look like the large all black model at the bottom of page 63. -- You can't have a sense of humor, if you have no sense. |
#10
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 14:14:45 -0800, John Larkin
wrote: On Sat, 19 Nov 2011 16:10:07 -0600, John Fields wrote: On Sat, 19 Nov 2011 13:32:41 -0800, John Larkin wrote: On Sat, 19 Nov 2011 12:49:59 -0600, John Fields wrote: Math errors in first two stages. --- It happens... Especially when you don't check your work, or even review it for reasonableness. --- Even when you do, it's more likely to happen again than if a different pair of eyes is checking it. --- Care to post the corrections? Lots of online calculators are available. --- I thought as much. -- JF |
#11
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 14:16:10 -0800, John Larkin
wrote: On Sat, 19 Nov 2011 15:31:07 -0500, "Michael A. Terrell" wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. They probably used pi, rather than tee, stages for some good reason. --- If you believe that's true, then what, in your vast store of knowledge might divine what their reasons be? And, BTW, since you posted that their attenuator comprises pi sections, the supposition is that you've reverse engineered their stuff, have found out what's in there and can post a schematic. Can you not do that and reveal, to all of us, their genius? -- JF |
#12
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sat, 19 Nov 2011 18:44:08 -0600, John Fields
wrote: On Sat, 19 Nov 2011 14:16:10 -0800, John Larkin wrote: On Sat, 19 Nov 2011 15:31:07 -0500, "Michael A. Terrell" wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. They probably used pi, rather than tee, stages for some good reason. --- If you believe that's true, then what, in your vast store of knowledge might divine what their reasons be? Probably too much inductance in the very small shunt leg resistors in a high-dB tee. Plus more inductance from having two resistors in the series path. But it's probably more complex than that. And, BTW, since you posted that their attenuator comprises pi sections, the supposition is that you've reverse engineered their stuff, Reverse engineered? No, I just looked at it. I like to open things up and see what's inside. This is one of my favorites: http://w140.com/tekwiki/wiki/SD-24 have found out what's in there and can post a schematic. Why? What they did is obvious from the photos. The only thing you might not know is that the short fat cylinders are caps. Can you not do that and reveal, to all of us, their genius? You are very, very weird. And not in a nice way. John |
#13
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6 bit binary attenuator. - 6 bit attenuator.pdf
John Larkin wrote: Reverse engineered? No, I just looked at it. I like to open things up and see what's inside. This is one of my favorites: http://w140.com/tekwiki/wiki/SD-24 Beautiful. -- Reply in group, but if emailing add one more zero, and remove the last word. |
#14
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6 bit binary attenuator. - 6 bit attenuator.pdf
On 11/19/2011 2:31 PM, Michael A. Terrell wrote:
John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build& test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. It was my understanding that getting over 20db of attenuation is difficult because of isolation and parasitics, especially for homebrewers. |
#15
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6 bit binary attenuator. - 6 bit attenuator.pdf
In message , amdx
writes On 11/19/2011 2:31 PM, Michael A. Terrell wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build& test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. It was my understanding that getting over 20db of attenuation is difficult because of isolation and parasitics, especially for homebrewers. I built such an attenuator around 1965 (and still have it somewhere). I think the steps were also 1/2/4/8/16/16/(16?) dB. Above 50MHz or so, at the higher attenuation settings, it was obvious that it was progressively yet another 'heroic failure'! Yes, the main limitation is the capacitance across the slide switches, and across the circuit as a whole. You can improve things by having each section in a screened compartment - and each needs to be essentially 'watertight', rather than having just simple screening walls between the switches. It would be interesting to know what degree of accuracy could be obtained if the nearest standard values of resistors (say, for both E12 and E24 series) were used. Obviously, using slightly 'wrong' values will affect both the attenuation and the RLR, so it would be necessary to decide on what compromises would be acceptable. Obviously each stage should be as accurate as possible in its own right, but it would also be important not to allow the errors to be 'all the same direction', so that their cumulation resulted in the overall accuracy of the attenuator progressively worsening as more stages were switched in, or if certain combinations were used. -- Ian |
#16
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6 bit binary attenuator. - 6 bit attenuator.pdf
Michael A. Terrell Inscribed thus:
Baron wrote: Michael A. Terrell Inscribed thus: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build & test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. Yes some toggle switches have poor isolation. I built one many years ago with slide switches. Above about 100Mhz an open switch only had about 38 - 39 Db attenuation. I think the contacts were far to close together for good performance. I now have a Rhode & Schwarz attenuator, good to at least 1Ghz. I have a couple Weinschel variable attenuators that are good past 5 GHz. Microdyne used them in their early telemetry test sets & C-band signal generators. They paid over $900 each, in the '90s. Some were replaced after a couple years on the test floor, the other is in a C-band sig generator to test commercial Sat equipment. http://www.aeroflex.com/ams/weinsche...S/stepattn.pdf they look like the large all black model at the bottom of page 63. Very nice ! I have a couple that look similar to the drum types but they are totally unmarked R&S ones that came out of an old Polyskop. I've no idea what the ratings are. The one I referred to in my OP is in a large steel box about 6 or 8 inches square and roughly 19 inches long with carrying handles on the ends fitted with "N" type connectors. I took the back off the case once ! When I saw all the rigid co-ax and silver boxes in there, I soon put it back on. Trouble is they don't get used very often. I'll have to dig it out and see what condition its now in. -- Best Regards: Baron. |
#17
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 01:13:54 -0500, "Tom Del Rosso"
wrote: John Larkin wrote: Reverse engineered? No, I just looked at it. I like to open things up and see what's inside. This is one of my favorites: http://w140.com/tekwiki/wiki/SD-24 Beautiful. Yes. Can you imagine how much engineering and tweaking went into that? This was before computational deconvolution could be used to clean up an ugly step response, so both the sampler and the TDR step generator had to be very, very clean, from DC to 20 GHz. And they are. Every little ground-to-ground wirebond, every weird little metalized shape, must be important. John |
#18
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 13:41:07 +0000, Ian Jackson
wrote: In message , amdx writes On 11/19/2011 2:31 PM, Michael A. Terrell wrote: John Fields wrote: Name: 6 bit attenuator.pdf 6 bit attenuator.pdf Type: Portable Document Format (application/pdf) Encoding: x-uuencode Did you build& test this? The literature I saw on this type of attenuator claimed that slide (or toggle) switches didn't have enough isolation between sections for an accurate 32 dB attenuator stage. That was why Kay used multiple 20 dB stages. It was my understanding that getting over 20db of attenuation is difficult because of isolation and parasitics, especially for homebrewers. I built such an attenuator around 1965 (and still have it somewhere). I think the steps were also 1/2/4/8/16/16/(16?) dB. Above 50MHz or so, at the higher attenuation settings, it was obvious that it was progressively yet another 'heroic failure'! Yes, the main limitation is the capacitance across the slide switches, and across the circuit as a whole. You can improve things by having each section in a screened compartment - and each needs to be essentially 'watertight', rather than having just simple screening walls between the switches. It would be interesting to know what degree of accuracy could be obtained if the nearest standard values of resistors (say, for both E12 and E24 series) were used. Obviously, using slightly 'wrong' values will affect both the attenuation and the RLR, so it would be necessary to decide on what compromises would be acceptable. Obviously each stage should be as accurate as possible in its own right, but it would also be important not to allow the errors to be 'all the same direction', so that their cumulation resulted in the overall accuracy of the attenuator progressively worsening as more stages were switched in, or if certain combinations were used. Cheap surface-mount resistors are good to many GHz, and crosstalk is low on a PC board with a ground plane. You could probably make a very nice step attenuator with 1% or 0.1% 1206 resistors and either small slide switches or telecom-type DPDT relays. A few R-C tweaks, like Kay did, would make it even better. John |
#19
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse
wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. John |
#20
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin
wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. Of course, your not being a chef and, therefore, having nothing but snide derision to offer - when the pudding is presented - will bitch about the lack of raisins without suggesting what their number should be -- JF |
#21
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 16:42:39 -0600, John Fields
wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. Of course, your not being a chef and, therefore, having nothing but snide derision to offer - when the pudding is presented - will bitch about the lack of raisins without suggesting what their number should be Raisins? How weird. John |
#22
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin
wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. --- Of course, your not being a chef and, therefore, having nothing but snide derision to offer - when the pudding is presented - will bitch about the lack of raisins without suggesting what their number should be Raisins? How weird. --- Q. What's a metaphor? A. Livestock to graze in. -- JF |
#23
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 17:56:24 -0600, John Fields
wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. --- Of course, your not being a chef and, therefore, having nothing but snide derision to offer - when the pudding is presented - will bitch about the lack of raisins without suggesting what their number should be Raisins? How weird. --- Q. What's a metaphor? A. Livestock to graze in. Sno-o-o-ort ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
#24
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 17:56:24 -0600, John Fields
wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. John |
#25
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6 bit binary attenuator. - 6 bit attenuator.pdf
John Larkin wrote: On Sun, 20 Nov 2011 01:13:54 -0500, "Tom Del Rosso" wrote: John Larkin wrote: Reverse engineered? No, I just looked at it. I like to open things up and see what's inside. This is one of my favorites: http://w140.com/tekwiki/wiki/SD-24 Beautiful. Yes. Can you imagine how much engineering and tweaking went into that? This was before computational deconvolution could be used to clean up an ugly step response, so both the sampler and the TDR step generator had to be very, very clean, from DC to 20 GHz. And they are. Every little ground-to-ground wirebond, every weird little metalized shape, must be important. I was especially wondering about the wire bonds between pads that are right next to each other! What's that for? (Considering that it doesn't look like they were attached at different points looking for a precise delay or something.) -- Reply in group, but if emailing add one more zero, and remove the last word. |
#26
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Sun, 20 Nov 2011 16:33:39 -0800, John Larkin
wrote: On Sun, 20 Nov 2011 17:56:24 -0600, John Fields wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. --- PKB, since didn't your recent little resistor fiasco come about because of excessive trust and inadequate sanity check? --- Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. Spare me the pontification of platitudes, blowhard. -- JF |
#27
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Mon, 21 Nov 2011 13:16:30 -0600, John Fields
wrote: On Sun, 20 Nov 2011 16:33:39 -0800, John Larkin wrote: On Sun, 20 Nov 2011 17:56:24 -0600, John Fields wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. --- PKB, since didn't your recent little resistor fiasco come about because of excessive trust and inadequate sanity check? Resistor fiasco? You mean the 0.05% thinfilms? Not the same thing at all. --- Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. Spare me the pontification of platitudes, blowhard. Check your math, doofus. John |
#28
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Mon, 21 Nov 2011 15:17:43 -0800, John Larkin
wrote: On Mon, 21 Nov 2011 13:16:30 -0600, John Fields wrote: On Sun, 20 Nov 2011 16:33:39 -0800, John Larkin wrote: On Sun, 20 Nov 2011 17:56:24 -0600, John Fields wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin m wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. --- PKB, since didn't your recent little resistor fiasco come about because of excessive trust and inadequate sanity check? Resistor fiasco? You mean the 0.05% thinfilms? Not the same thing at all. --- ISTR that you trusted your vendor enough to supply you with the right stuff that you didn't do the sanity check of an incoming inspection and, consequently, you got bit on the ass for your fox paws. Which airplanes do you have stuff flying on, or you supply GSE for, anyway? --- Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. Spare me the pontification of platitudes, blowhard. Check your math, doofus. --- All in good time, and at my leisure. -- JF |
#29
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Tue, 22 Nov 2011 01:45:25 -0600, John Fields
wrote: On Mon, 21 Nov 2011 15:17:43 -0800, John Larkin wrote: On Mon, 21 Nov 2011 13:16:30 -0600, John Fields wrote: On Sun, 20 Nov 2011 16:33:39 -0800, John Larkin wrote: On Sun, 20 Nov 2011 17:56:24 -0600, John Fields wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. --- PKB, since didn't your recent little resistor fiasco come about because of excessive trust and inadequate sanity check? Resistor fiasco? You mean the 0.05% thinfilms? Not the same thing at all. --- ISTR that you trusted your vendor enough to supply you with the right stuff that you didn't do the sanity check of an incoming inspection and, consequently, you got bit on the ass for your fox paws. We have 5325 different parts in stock, 2.08 million pieces, so things like that happen once in a while. We can't possibly incoming inspect every part we buy. Imagine setting up test jigs for opamps, microprocessors, FPGAs, bare PC boards, transformers, sheet matal, all that. I have done flight hardware for spacecraft, where every single part is tested and certified and traceable, and that's absurdly expensive. We do have procedures for picking up on parts problems in production test, or from field returns, and investigating any patterns. That's how we caught the resistor problem. In fact, it was a BIST reutine run on an RTD acquisition section that found it, namely a circuit that uses two resistors and checks them against one another. Which airplanes do you have stuff flying on, or you supply GSE for, anyway? We don't have much actually flying. Some on the U2, some heads-up display stuff on some AH130s. Most of our stuff is used in engine and FADEC development and test cells (United Airlines uses our gear to test APUs). We do some ground test stuff for B52 radars. That's a good mix, aerospace but no mil or FAA certifications, which are a lot of work. --- Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. Spare me the pontification of platitudes, blowhard. Check your math, doofus. --- All in good time, and at my leisure. Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. John |
#30
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6 bit binary attenuator. - 6 bit attenuator.pdf
John Larkin Inscribed thus:
Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. John Now that could be a good idea ! But it shouldn't prevent checking and confirming a result. :-) -- Best Regards: Baron. |
#31
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Tue, 22 Nov 2011 22:40:14 +0000, Baron
wrote: John Larkin Inscribed thus: Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. John Now that could be a good idea ! But it shouldn't prevent checking and confirming a result. :-) We could start a list of bad online circuit "designs" by Larkin ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
#32
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6 bit binary attenuator. - 6 bit attenuator.pdf
On 11/22/2011 5:15 PM, Jim Thompson wrote:
On Tue, 22 Nov 2011 22:40:14 +0000, wrote: John Larkin Inscribed thus: Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. John Now that could be a good idea ! But it shouldn't prevent checking and confirming a result. :-) We could start a list of bad online circuit "designs" by Larkin ;-) ...Jim Thompson Very second-childhoodish of you Jim. |
#33
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Tue, 22 Nov 2011 17:40:28 -0600, John S
wrote: On 11/22/2011 5:15 PM, Jim Thompson wrote: On Tue, 22 Nov 2011 22:40:14 +0000, wrote: John Larkin Inscribed thus: Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. John Now that could be a good idea ! But it shouldn't prevent checking and confirming a result. :-) We could start a list of bad online circuit "designs" by Larkin ;-) ...Jim Thompson Very second-childhoodish of you Jim. Heck, he's up to childhood 2.5. John |
#34
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6 bit binary attenuator. - 6 bit attenuator.pdf
On Tue, 22 Nov 2011 08:18:23 -0800, John Larkin
wrote: On Tue, 22 Nov 2011 01:45:25 -0600, John Fields wrote: On Mon, 21 Nov 2011 15:17:43 -0800, John Larkin wrote: On Mon, 21 Nov 2011 13:16:30 -0600, John Fields wrote: On Sun, 20 Nov 2011 16:33:39 -0800, John Larkin wrote: On Sun, 20 Nov 2011 17:56:24 -0600, John Fields wrote: On Sun, 20 Nov 2011 15:06:52 -0800, John Larkin m wrote: On Sun, 20 Nov 2011 16:42:39 -0600, John Fields wrote: On Sun, 20 Nov 2011 09:25:29 -0800, John Larkin m wrote: On Sun, 20 Nov 2011 08:16:21 -0800, Fred Abse wrote: On Sat, 19 Nov 2011 14:14:45 -0800 John Larkin wrote: Lots of online calculators are available. I use this. I'm not sure how good or otherwise it looks in Excel, it was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it. It produces theoretically image-matched attenuators for any combination of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values. Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions. I wrote it about 30 years ago, as an HP41CV calculator app, and subsequently made a spreadsheet out of it. See attached file. Ooh, very nice. Thanks. JF can use that to fix up his design. --- Actually, I'm close to fixing the math errors in my design, which seem to have come from a trusted source, and which I'll post when I'm done. You must mean formerly trusted source. --- Nope, they're still trusted, by-and-large, because of previous flawless performance. If I get a bad hit again, though, they'll bear a little closer watching. Kinda like where you are now, where truth bows to face and I must therefore consider you less than trustworthy. All you have to do is look at the values of the first tee, which I did, and it's obvious that it won't attenuate 32 dB. I don't trust anything without giving it a sanity check. --- PKB, since didn't your recent little resistor fiasco come about because of excessive trust and inadequate sanity check? Resistor fiasco? You mean the 0.05% thinfilms? Not the same thing at all. --- ISTR that you trusted your vendor enough to supply you with the right stuff that you didn't do the sanity check of an incoming inspection and, consequently, you got bit on the ass for your fox paws. We have 5325 different parts in stock, 2.08 million pieces, so things like that happen once in a while. We can't possibly incoming inspect every part we buy. --- Then you're substituting trust for incoming test and are willing to take the production test fallout/repair cycle. --- Imagine setting up test jigs for opamps, microprocessors, FPGAs, bare PC boards, transformers, sheet matal, all that. --- Imagine? It isn't hard to do, but for you it seems to be a question of economics, and you're willing to initially trust vendors' spec's and apply salve to the wounds when the parts fall short. Or long. --- I have done flight hardware for spacecraft, where every single part is tested and certified and traceable, and that's absurdly expensive. --- Yeah, but just consider the alternative. :-( --- We do have procedures for picking up on parts problems in production test, or from field returns, and investigating any patterns. That's how we caught the resistor problem. In fact, it was a BIST reutine run on an RTD acquisition section that found it, namely a circuit that uses two resistors and checks them against one another. Which airplanes do you have stuff flying on, or you supply GSE for, anyway? We don't have much actually flying. Some on the U2, some heads-up display stuff on some AH130s. Most of our stuff is used in engine and FADEC development and test cells (United Airlines uses our gear to test APUs). We do some ground test stuff for B52 radars. That's a good mix, aerospace but no mil or FAA certifications, which are a lot of work. --- Agreed. --- Trust is no substitute for checking. As systems get more complex, the margin for risk goes down. Spare me the pontification of platitudes, blowhard. Check your math, doofus. --- All in good time, and at my leisure. Did you use one of those online calculators? --- No, I used the formulas and the table, attached, from the 7th edition of the ITT Handbook, ISBN 0-672-21563-2. I just plucked the values for 1, 2, 4, and 8dB from the table, and calculated the values of the resistances for 16 and 32 dB pads using the formulas. Using their notation for a tee pad: .. o---[a]-+-[a]---o .. | .. [b] .. | .. o-------+-------o with input and output resistances (R0) of one ohm, they state that: dB/20 dB/20 a = (10^ -1) / (10^ +1) ohms and dB/20 dB/10 b = 2.1^ / (10^ -1) and, that for values of R0 not equal to one ohm, the calculated values of the resistances should be multiplied by the desired R0. Since you found errors, I decided to run my numbers again, and especially to run them at 10dB, where they could be double-checked against the table and the formulas. I also ran the numbers from the 10dB table entry through LTspice and found them to be rock-solid for dB = 10 log P1/P2 and dB = 20 log V1/V2. I've attached my hand calculations, using the formulas from the book, for your perusal. If you don't want to get that deep into it, here's a summary: ATTEN Ra Rb dB ohms ohms ----|--------|------ 10 25.973 8.05 16 36.318 2.22 32 47.5 0.1 Interesting to note is that for the 10dB entry, the values of Ra - according to the table and the formula - are identical, but the values of Rb are not. Using LTspice as a referee, it turns out that the values given in the table are perfect, but those calculated using the formulas are not. So where's the error? A typo in the book. It turns out that in the formula for b, dB/20 dB/10 b = 2.1^ / (10^ -1), the decimal point between the 2 and the 1 should actually be a dot indicating multiplication, and the formula for Rb in a 50 ohm pad would then be: dB/20 dB/10 Rb = 2 * 50^ / (10^ -1) Using that formula gives: ATTEN Ra Rb dB ohms ohms ----|-------|------ 10 25.97 35.14 16 36.32 16.26 32 47.55 2.51 BTW, here's where I found that the error was in the book: http://www.microwaves101.com/encyclo...attenuator.cfm A lot of them are plain wrong. --- I'm surprised, then, that in an earlier post you didn't offer me a leg up by referring me to one which you knew wasn't flawed. --- I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places. A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance. We could start a list of bad online calculators. --- I don't care to, but YMMV. -- JF |
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