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.

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.

On Sat, 19 Nov 2011 12:49:59 -0600, John Fields
wrote:


Math errors in first two stages.

John

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

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

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

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

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.

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

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

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

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.

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.

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

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.

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

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

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

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

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

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

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.

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

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.

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

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

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

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

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.

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.

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.

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

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