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A resistor network with a curious property

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  A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-22 20:23 -0500
    Re: A resistor network with a curious property George Herold <gherold@teachspin.com> - 2017-03-22 19:11 -0700
      Re: A resistor network with a curious property George Herold <gherold@teachspin.com> - 2017-03-22 19:49 -0700
        Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-22 23:43 -0500
      Re: A resistor network with a curious property Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-23 10:56 -0400
        Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 02:15 -0500
    Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-22 22:24 -0400
    Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-22 23:05 -0400
      Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-22 23:44 -0500
        Re: A resistor network with a curious property Jasen Betts <jasen@xnet.co.nz> - 2017-03-23 07:20 +0000
    Re: A resistor network with a curious property Robert Baer <robertbaer@localnet.com> - 2017-03-22 19:48 -0800
      Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-22 23:47 -0500
    Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 21:20 -0700
      Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-22 23:55 -0500
        Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-23 01:15 -0400
          Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 02:41 -0500
            Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-25 09:45 -0400
        Re: A resistor network with a curious property Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2017-03-23 09:16 +0000
          Re: A resistor network with a curious property Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2017-03-23 14:51 +0000
        Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 08:41 -0700
          Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 03:30 -0500
            Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 09:25 -0700
            Re: A resistor network with a curious property George Herold <gherold@teachspin.com> - 2017-03-25 09:59 -0700
              Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 15:25 -0500
      Re: A resistor network with a curious property Winfield Hill <hill@rowland.harvard.edu> - 2017-03-23 12:38 -0700
    Re: A resistor network with a curious property "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-23 06:41 +0000
    Re: A resistor network with a curious property Wanderer <wanderer@dialup4less.com> - 2017-03-23 05:53 -0700
      Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-23 13:41 -0400
      Re: A resistor network with a curious property rickman <gnuarm@gmail.com> - 2017-03-25 18:57 -0400
    Re: A resistor network with a curious property Jon Elson <jmelson@wustl.edu> - 2017-03-23 14:28 -0500
      Re: A resistor network with a curious property tabbypurr@gmail.com - 2017-03-23 20:59 -0700
        Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 09:27 -0700
      Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 02:58 -0500
        Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 09:31 -0700
          Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-25 15:32 -0500
            Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 13:54 -0700
              Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-25 17:26 -0400
                Re: A resistor network with a curious property "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-26 02:51 -0500
                  Re: A resistor network with a curious property bitrex <bitrex@de.lete.earthlink.net> - 2017-03-26 12:18 -0400
              Re: A resistor network with a curious property whit3rd <whit3rd@gmail.com> - 2017-03-25 16:11 -0700
                Re: A resistor network with a curious property John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-26 11:36 -0700
      Re: A resistor network with a curious property rickman <gnuarm@gmail.com> - 2017-03-25 18:57 -0400
    Re: A resistor network with a curious property bloggs.fredbloggs.fred@gmail.com - 2017-03-24 09:08 -0700

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#453539

"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
news:qgq7dc5p2oroebe1vbvqi8clrddjivitj5@4ax.com...
>>> Why is it not symmetric?
>>
>>You mean left to right? ...How could it?
>
> Well, symmetric with equal power dissipation per unit length would be
> a challenge.

The contrasting subjective experiences of "challenge" seen in this thread 
are interesting to me.  Bitrex seems to think it's in some way intractible; 
I think it's no worse than quadratic (and some others seem to support that 
intuition); and you think it's a "challenge" (not for the given problem, 
which was solved to your satisfaction -- if it has numbers, it works -- but 
for a related problem, which is always fun to think about).

Yet for this related problem, I can instantly see why that cannot be.  (I 
have the unfair advantage of having created and solved the problem in the 
first place.  Not trying to rub it in, but I think I'd like to leave the 
answer to be puzzled out, so I won't show why, right now anyway.)

So I wonder if your sense of "challenge" is calibrated more along the lines 
of a manager -- it calls to mind some recent debacles from the crowdfunding 
world: their managers seem to well and truly believe that "we'll solve it in 
development", nevermind that what they're trying to solve happens to be 
thermodynamics itself!

Fortunately, you know better than to fight thermodynamics itself, but the 
fact remains: if it's not immediately obvious that the problem being solved 
is equivalent to thermodynamics, or causality, or something like that, then 
you want to continue pushing for that solution, as long as it might be 
possible.

It's not an indictment of your scientific knowledge, indeed it's a very 
practical, managery thing to do, to push for a solution regardless of the 
nature of the problem.  I mean very specifically that it's a "calibration of 
'challenge'".  It's not practical for a manager to have complete knowledge 
of the subproblems going into their projects, it's only their duty to make 
sure they get solved.  And, if it should happen that the problems cannot be 
solved, adjust the schedule or project design to avoid that pitfall.

I just think it's interesting to see different worldviews applied to the 
perception of a problem.


> I'm thinking about an old HP APC7 attenuator, 20 GHz or something.
> Inside looks like a sheet of glass with a really pretty blue film on
> top.

Hmm, metal thin film, perhaps?  Or maybe a conductive plastic that happens 
to have that color.  Fun in any case.


> Here's a MiniCircuits trimmed thinfilm:
>
> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01870.JPG
>
> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01874.JPG
>
> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01876.JPG
>

Looks like they did a pi attenuator, more or less, which limits power on the 
first resistor, probably.  What is that, 1/2W or 1W, something around there?

Interesting that they have a bunch of unused pads on that substrate.  I 
wonder if they use the same substrate, with different carbon tracks and 
bond-outs, for a whole slew of parts.


> What sort of power and frequency range did you have in mind? Or is
> this a theoretical exercize?
>
> Plain cheap 0805 resistors are fine to several GHz. Those values might
> be hard to get from Digikey.

Close enough values are certainly available in spades; the resulting network 
would only be good to a watt or two, though.  You could just as well make a 
couple low-dB attenuators (in the 1-10dB range) out of 1218s or 2512s, to 
get a couple watts out of chip resistors, without sacrificing much 
bandwidth.

My initial concept was to use thick film power resistors (TO-220 style, and 
the like), without simply connecting them in series-parallel (which would 
worsen the frequency response).  Now that I've shown the equi-power network 
exists, it should be quite achievable to do 200-1000W with these parts, with 
good performance into the 100s of MHz.  Which is far more than anything I 
have on my project list at the moment, so I'm happy. :)

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

[toc] | [prev] | [next] | [standalone]

#453564

On Sat, 25 Mar 2017 03:30:45 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
>news:qgq7dc5p2oroebe1vbvqi8clrddjivitj5@4ax.com...
>>>> Why is it not symmetric?
>>>
>>>You mean left to right? ...How could it?
>>
>> Well, symmetric with equal power dissipation per unit length would be
>> a challenge.
>
>The contrasting subjective experiences of "challenge" seen in this thread 
>are interesting to me.  Bitrex seems to think it's in some way intractible; 
>I think it's no worse than quadratic (and some others seem to support that 
>intuition); and you think it's a "challenge" (not for the given problem, 
>which was solved to your satisfaction -- if it has numbers, it works -- but 
>for a related problem, which is always fun to think about).
>
>Yet for this related problem, I can instantly see why that cannot be.  (I 
>have the unfair advantage of having created and solved the problem in the 
>first place.  Not trying to rub it in, but I think I'd like to leave the 
>answer to be puzzled out, so I won't show why, right now anyway.)
>
>So I wonder if your sense of "challenge" is calibrated more along the lines 
>of a manager -- it calls to mind some recent debacles from the crowdfunding 
>world: their managers seem to well and truly believe that "we'll solve it in 
>development", nevermind that what they're trying to solve happens to be 
>thermodynamics itself!

I'm a design engineer, not a scientist, not a manager. I hire people
to manage my company and manage me. If I need serious theory, I know
people who can do it for me.

I am very Irish and practical, so I prefer numerical solutions to
abstract ones, and experiment to theory. I build things.

I respect physics and thermo, in the sense that I realize that I can't
violate first principles and shouldn't waste my time trying. But I
also don't allow tradition or restricted visions of theory to prevent
me from considering new ideas for products.


>
>Fortunately, you know better than to fight thermodynamics itself, but the 
>fact remains: if it's not immediately obvious that the problem being solved 
>is equivalent to thermodynamics, or causality, or something like that, then 
>you want to continue pushing for that solution, as long as it might be 
>possible.

Yes; but within reason and attention span. As Facebook says, done is
better than perfect.

Causality and conservation of energy seem to matter. LC filters
involve both.


>
>It's not an indictment of your scientific knowledge, indeed it's a very 
>practical, managery thing to do, to push for a solution regardless of the 
>nature of the problem.  I mean very specifically that it's a "calibration of 
>'challenge'".  It's not practical for a manager to have complete knowledge 
>of the subproblems going into their projects, it's only their duty to make 
>sure they get solved.  And, if it should happen that the problems cannot be 
>solved, adjust the schedule or project design to avoid that pitfall.

I don't have pretensions to scientific knowledge. I passed the usual
college courses in physics and chemistry and thermo and materials and
electromagnetics, and they mostly trained my instincts as opposed to
encouraging me to cover pages with equations. 

>
>I just think it's interesting to see different worldviews applied to the 
>perception of a problem.
>
>
>> I'm thinking about an old HP APC7 attenuator, 20 GHz or something.
>> Inside looks like a sheet of glass with a really pretty blue film on
>> top.
>
>Hmm, metal thin film, perhaps?  Or maybe a conductive plastic that happens 
>to have that color.  Fun in any case.
>
>
>> Here's a MiniCircuits trimmed thinfilm:
>>
>> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01870.JPG
>>
>> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01874.JPG
>>
>> https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01876.JPG
>>
>
>Looks like they did a pi attenuator, more or less, which limits power on the 
>first resistor, probably.  What is that, 1/2W or 1W, something around there?

The VAT20 is 1/2 watt, only moderate bandwidth. It's a cheap
attenuator, the kind you buy a bunch of for the bench.

An attenuator, like that HP thing, need not have an equivalent lumped
schematic.

>
>Interesting that they have a bunch of unused pads on that substrate.  I 
>wonder if they use the same substrate, with different carbon tracks and 
>bond-outs, for a whole slew of parts.

Likely.

I've long been intrigued by those giant (like cubic foot) GHz KW
heatsink-finned power attenuators and terminators. How can anything
that big be fast?

>
>
>> What sort of power and frequency range did you have in mind? Or is
>> this a theoretical exercize?
>>
>> Plain cheap 0805 resistors are fine to several GHz. Those values might
>> be hard to get from Digikey.
>
>Close enough values are certainly available in spades; the resulting network 
>would only be good to a watt or two, though.  You could just as well make a 
>couple low-dB attenuators (in the 1-10dB range) out of 1218s or 2512s, to 
>get a couple watts out of chip resistors, without sacrificing much 
>bandwidth.

You can buy small AlN-substrate terminators and attenuators, rated for
hundreds of watts if you can heat sink them somehow.


>
>My initial concept was to use thick film power resistors (TO-220 style, and 
>the like), without simply connecting them in series-parallel (which would 
>worsen the frequency response).  Now that I've shown the equi-power network 
>exists, it should be quite achievable to do 200-1000W with these parts, with 
>good performance into the 100s of MHz.  Which is far more than anything I 
>have on my project list at the moment, so I'm happy. :)

Have you looked at the Caddock axial super-wideband resistors? They
are handy for making several-kilovolt several-GHz pulse attenuators.

https://dl.dropboxusercontent.com/u/53724080/Gear/HP/HP54006_probe.zip



-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

[toc] | [prev] | [next] | [standalone]

#453572

On Saturday, March 25, 2017 at 4:30:45 AM UTC-4, Tim Williams wrote:
> "John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
> news:qgq7dc5p2oroebe1vbvqi8clrddjivitj5@4ax.com...
> >>> Why is it not symmetric?
> >>
> >>You mean left to right? ...How could it?
> >
> > Well, symmetric with equal power dissipation per unit length would be
> > a challenge.
> 
> The contrasting subjective experiences of "challenge" seen in this thread 
> are interesting to me.  Bitrex seems to think it's in some way intractible; 
> I think it's no worse than quadratic (and some others seem to support that 
> intuition); and you think it's a "challenge" (not for the given problem, 
> which was solved to your satisfaction -- if it has numbers, it works -- but 
> for a related problem, which is always fun to think about).
> 
> Yet for this related problem, I can instantly see why that cannot be.  (I 
> have the unfair advantage of having created and solved the problem in the 
> first place.  Not trying to rub it in, but I think I'd like to leave the 
> answer to be puzzled out, so I won't show why, right now anyway.)
> 
> So I wonder if your sense of "challenge" is calibrated more along the lines 
> of a manager -- it calls to mind some recent debacles from the crowdfunding 
> world: their managers seem to well and truly believe that "we'll solve it in 
> development", nevermind that what they're trying to solve happens to be 
> thermodynamics itself!
> 
> Fortunately, you know better than to fight thermodynamics itself, but the 
> fact remains: if it's not immediately obvious that the problem being solved 
> is equivalent to thermodynamics, or causality, or something like that, then 
> you want to continue pushing for that solution, as long as it might be 
> possible.
> 
> It's not an indictment of your scientific knowledge, indeed it's a very 
> practical, managery thing to do, to push for a solution regardless of the 
> nature of the problem.  I mean very specifically that it's a "calibration of 
> 'challenge'".  It's not practical for a manager to have complete knowledge 
> of the subproblems going into their projects, it's only their duty to make 
> sure they get solved.  And, if it should happen that the problems cannot be 
> solved, adjust the schedule or project design to avoid that pitfall.
> 
> I just think it's interesting to see different worldviews applied to the 
> perception of a problem.
> 
> 
> > I'm thinking about an old HP APC7 attenuator, 20 GHz or something.
> > Inside looks like a sheet of glass with a really pretty blue film on
> > top.
> 
> Hmm, metal thin film, perhaps?  Or maybe a conductive plastic that happens 
> to have that color.  Fun in any case.
> 
> 
> > Here's a MiniCircuits trimmed thinfilm:
> >
> > https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01870.JPG
> >
> > https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01874.JPG
> >
> > https://dl.dropboxusercontent.com/u/53724080/Gear/Mini-Ckts/DSC01876.JPG
> >
> 
> Looks like they did a pi attenuator, more or less, which limits power on the 
> first resistor, probably.  What is that, 1/2W or 1W, something around there?
> 
> Interesting that they have a bunch of unused pads on that substrate.  I 
> wonder if they use the same substrate, with different carbon tracks and 
> bond-outs, for a whole slew of parts.
> 
> 
> > What sort of power and frequency range did you have in mind? Or is
> > this a theoretical exercize?
> >
> > Plain cheap 0805 resistors are fine to several GHz. Those values might
> > be hard to get from Digikey.
> 
> Close enough values are certainly available in spades; the resulting network 
> would only be good to a watt or two, though.  You could just as well make a 
> couple low-dB attenuators (in the 1-10dB range) out of 1218s or 2512s, to 
> get a couple watts out of chip resistors, without sacrificing much 
> bandwidth.
> 
> My initial concept was to use thick film power resistors (TO-220 style, and 
> the like), without simply connecting them in series-parallel (which would 
> worsen the frequency response).  Now that I've shown the equi-power network 
> exists, it should be quite achievable to do 200-1000W with these parts, with 
> good performance into the 100s of MHz.  Which is far more than anything I 
> have on my project list at the moment, so I'm happy. :)
Ahh, OK I was wondering what the goal was...  Why is your network 
better than than just a string of ~10 20W TO-220's?  (With some other 
 R's (in the Tee) to keep 50 ohms everywhere.)
I don't know much about R's at high frequency.

George H.   
> 
> Tim
> 
> -- 
> Seven Transistor Labs, LLC
> Electrical Engineering Consultation and Contract Design
> Website: http://seventransistorlabs.com

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#453602

"George Herold" <gherold@teachspin.com> wrote in message 
news:d9da8e97-7e1f-415b-adf4-0d65437fe7d7@googlegroups.com...
> Ahh, OK I was wondering what the goal was...  Why is your network
> better than than just a string of ~10 20W TO-220's?  (With some other
> R's (in the Tee) to keep 50 ohms everywhere.)
> I don't know much about R's at high frequency.

The low-order equivalent circuit of a TO-220 resistor will be two series 
inductors, representing lead (and bond, if applicable) inductance, a 
resistance between them, and a distributed capacitance from the resistor to 
the heatsink tab and other surroundings.

Really, the leads will have a transmission line impedance on the order of 
150 ohms, which looks inductive at lower frequencies and lower impedances 
(say, relative to 50 ohms).  The resistive patch will have some transmission 
line characteristic as well, and if it evenly covers the substrate, it will 
have a low impedance, and therefore look capacitive at lower frequencies.

"Lower frequencies" being, those well below the equivalent electrical length 
of the elements in question.  So, for a TO-220, a couple cm -- a couple GHz.

At higher frequencies, you cannot so easily ignore the transmission line 
effects, and you have to build more and more complicated (higher order) 
lumped models (distributed L and C) to suit (or use transmission lines 
proper).

But at that point, you'll have so much trouble matching to these structures, 
and in keeping them consistent between assemblies (because we're talking 
lead geometry here), that you're better off giving up and declaring that as 
your upper frequency limit...

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#453257

John Larkin wrote...
>
> "Tim Williams" wrote:
>
>>https://www.seventransistorlabs.com/Images/DistAttenuator.png
>
> Trying to distribute the power dissipation?

 Each resistor dissipates about 10% of the total,
 so with 1/4-watt resistors, the whole thing can
 be rated for about 5W.  A 40dB 5W attenuator.
 Now just to source all those odd 0.001% values.


-- 
 Thanks,
    - Win

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#453204

"Tim Williams"  wrote in message news:oav7t0$99t$1@dont-email.me...

>https://www.seventransistorlabs.com/Images/DistAttenuator.png

>Solved by minimization... should like to come up with the equation that 
>generates it, though.

Why? This universe has billions of nonlinear equations, all unsolvable by 
direct methods....

-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html 

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#453216

On Wednesday, March 22, 2017 at 9:23:30 PM UTC-4, Tim Williams wrote:
> https://www.seventransistorlabs.com/Images/DistAttenuator.png
> 
> Solved by minimization... should like to come up with the equation that 
> generates it, though.
> 
> Tim
> 
> -- 
> Seven Transistor Labs, LLC
> Electrical Engineering Consultation and Contract Design
> Website: http://seventransistorlabs.com

I don't get it.

def resnet():
    Rs =  [0.00,
           4.975589275,
           407.4288442,
           6.288703772,
           312.41813304,
           8.53980209,
           217.7050614,
           13.27885061,
           123.4502975,
           29.4024347,
           32.35807277,
           633.5919372,
           54.12833875]
    
    Rnode = [0]
    Rsum =  Rs[12]
    j = 5
    for i in range(10,0,-2):
        Rsum += Rs[i+1]
        Rsum = (Rsum * Rs[i])/(Rsum +Rs[i])
        Rnode.append(Rsum)
        print "Resistance after V%d is %.6f" % (j, Rsum)
        j -=1 
    Rsum += Rs[1]
    Rnode.append(Rsum) 
    print "Resistance after V0 is %.6f" % (Rsum)
    print Rnode
    print
    
    Rratio = []
    for i in range(1,6,1):
        Rratio.append(Rnode[i]/Rnode[i+1])
        print "V%d = V%d * %.4f" % (i, i-1, Rnode[i]/Rnode[i+1])
    print Rratio
    print
    
    Rrat = 1.0
    for i in range(5):
        Rrat *= Rratio[i]
        print "V%d = V0 * %.4f" % (i+1, Rrat)




The Output is:

Resistance after V5 is 30.904002
Resistance after V4 is 40.514692
Resistance after V3 is 43.135126
Resistance after V2 is 44.340819
Resistance after V1 is 45.033405
Resistance after V0 is 50.008994
[0, 30.904002007769993, 40.51469234494225, 43.135126236666615, 44.34081927349529, 45.03340519870456, 50.008994473704554]

V1 = V0 * 0.7628
V2 = V1 * 0.9393
V3 = V2 * 0.9728
V4 = V3 * 0.9846
V5 = V4 * 0.9005
[0.7627850594212391, 0.9392505802035443, 0.9728085079034753, 0.9846206183575656, 0.9005061124031152]

V1 = V0 * 0.7628
V2 = V0 * 0.7164
V3 = V0 * 0.6970
V4 = V0 * 0.6862
V5 = V0 * 0.6180

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#453244

On 03/23/2017 08:53 AM, Wanderer wrote:
> On Wednesday, March 22, 2017 at 9:23:30 PM UTC-4, Tim Williams wrote:
>> https://www.seventransistorlabs.com/Images/DistAttenuator.png
>>
>> Solved by minimization... should like to come up with the equation that
>> generates it, though.
>>
>> Tim
>>
>> --
>> Seven Transistor Labs, LLC
>> Electrical Engineering Consultation and Contract Design
>> Website: http://seventransistorlabs.com
>
> I don't get it.
>

<snip>

I can "see" that you write your Python like "C"...;-)

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#453619

On 3/23/2017 8:53 AM, Wanderer wrote:
> On Wednesday, March 22, 2017 at 9:23:30 PM UTC-4, Tim Williams wrote:
>> https://www.seventransistorlabs.com/Images/DistAttenuator.png
>>
>> Solved by minimization... should like to come up with the equation that
>> generates it, though.
>>
>> Tim
>>
>> --
>> Seven Transistor Labs, LLC
>> Electrical Engineering Consultation and Contract Design
>> Website: http://seventransistorlabs.com
>
> I don't get it.
>
> def resnet():
>     Rs =  [0.00,
>            4.975589275,
>            407.4288442,
>            6.288703772,
>            312.41813304,
>            8.53980209,
>            217.7050614,
>            13.27885061,
>            123.4502975,
>            29.4024347,
>            32.35807277,
>            633.5919372,
>            54.12833875]
>
>     Rnode = [0]
>     Rsum =  Rs[12]
>     j = 5
>     for i in range(10,0,-2):
>         Rsum += Rs[i+1]
>         Rsum = (Rsum * Rs[i])/(Rsum +Rs[i])
>         Rnode.append(Rsum)
>         print "Resistance after V%d is %.6f" % (j, Rsum)
>         j -=1
>     Rsum += Rs[1]
>     Rnode.append(Rsum)
>     print "Resistance after V0 is %.6f" % (Rsum)
>     print Rnode
>     print
>
>     Rratio = []
>     for i in range(1,6,1):
>         Rratio.append(Rnode[i]/Rnode[i+1])
>         print "V%d = V%d * %.4f" % (i, i-1, Rnode[i]/Rnode[i+1])
>     print Rratio
>     print
>
>     Rrat = 1.0
>     for i in range(5):
>         Rrat *= Rratio[i]
>         print "V%d = V0 * %.4f" % (i+1, Rrat)
>
>
>
>
> The Output is:
>
> Resistance after V5 is 30.904002
> Resistance after V4 is 40.514692
> Resistance after V3 is 43.135126
> Resistance after V2 is 44.340819
> Resistance after V1 is 45.033405
> Resistance after V0 is 50.008994
> [0, 30.904002007769993, 40.51469234494225, 43.135126236666615, 44.34081927349529, 45.03340519870456, 50.008994473704554]
>
> V1 = V0 * 0.7628
> V2 = V1 * 0.9393
> V3 = V2 * 0.9728
> V4 = V3 * 0.9846
> V5 = V4 * 0.9005
> [0.7627850594212391, 0.9392505802035443, 0.9728085079034753, 0.9846206183575656, 0.9005061124031152]
>
> V1 = V0 * 0.7628
> V2 = V0 * 0.7164
> V3 = V0 * 0.6970
> V4 = V0 * 0.6862
> V5 = V0 * 0.6180

What happened to Vout?

I'd use a spread sheet for this.  Spread sheets are pretty functional 
and easy to do.

-- 

Rick C

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#453255

Tim Williams wrote:

> https://www.seventransistorlabs.com/Images/DistAttenuator.png
> 
> Solved by minimization... should like to come up with the equation that
> generates it, though.
> 
> Tim
> 
Where do you get those resistors with 10 significant digits?

Hmmm, they must have a warehouse the size of the earth to stock all the 
different values.

Jon

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#453331

On Thursday, 23 March 2017 19:27:41 UTC, Jon Elson  wrote:
> Tim Williams wrote:
> 
> > https://www.seventransistorlabs.com/Images/DistAttenuator.png
> > 
> > Solved by minimization... should like to come up with the equation that
> > generates it, though.
> > 
> > Tim
> > 
> Where do you get those resistors with 10 significant digits?
> 
> Hmmm, they must have a warehouse the size of the earth to stock all the 
> different values.
> 
> Jon

No, it's a sensible size... but whatever value you want always seems to be out of stock.


NT

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#453565

On Thu, 23 Mar 2017 20:59:16 -0700 (PDT), tabbypurr@gmail.com wrote:

>On Thursday, 23 March 2017 19:27:41 UTC, Jon Elson  wrote:
>> Tim Williams wrote:
>> 
>> > https://www.seventransistorlabs.com/Images/DistAttenuator.png
>> > 
>> > Solved by minimization... should like to come up with the equation that
>> > generates it, though.
>> > 
>> > Tim
>> > 
>> Where do you get those resistors with 10 significant digits?
>> 
>> Hmmm, they must have a warehouse the size of the earth to stock all the 
>> different values.
>> 
>> Jon
>
>No, it's a sensible size... but whatever value you want always seems to be out of stock.
>

Digikey, to be exact.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453531

"Jon Elson" <jmelson@wustl.edu> wrote in message 
news:3-udnS6r08w5vEnFnZ2dnUU7-NmdnZ2d@giganews.com...
> Where do you get those resistors with 10 significant digits?
>
> Hmmm, they must have a warehouse the size of the earth to stock all the
> different values.

In practice, quite good results would be had with 1% resistors (i.e., power 
matching to 2%, SWR < 1.01).  I didn't bother truncating the decimals, it 
looks more impressive that way. ;-D

You might not even get 1% values in power resistors (say for a 100W+ 
version), necessitating some stacking of series and parallel values to get 
acceptable accuracy.

Likely, quite a good tradeoff (better than 10%) can be found just by playing 
around with the set of nearest E6 values.

I wonder how much effect the physical length of the resistor will have.  At 
frequencies where the resistor itself is 1/4 wavelength long, the 
transmission line length has the effect of 1/4-wave-transformering half of 
the resistor from a series equivalent to a parallel equivalent, or vice 
versa.  The effect is higher loss per resistor.  The SWR should change 
slightly at very high frequencies, but more importantly, the power gets 
concentrated towards the beginning of the network, reducing its ultimate 
power limit.  (Skin effect will behave similarly, too.)

Resistors with high impedances (aka inductive wirewound resistors) would 
also be problematic for the series resistors, but not necessarily a big 
issue for the early parallel resistors (which may have values on par with 
their AC impedances).  As the series and parallel values both converge 
towards 50 ohms, the characteristic impedance should converge as well, 
making bulk film parts more desirable than wound or sinuous-path-etched 
parts.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#453566

On Sat, 25 Mar 2017 02:58:27 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"Jon Elson" <jmelson@wustl.edu> wrote in message 
>news:3-udnS6r08w5vEnFnZ2dnUU7-NmdnZ2d@giganews.com...
>> Where do you get those resistors with 10 significant digits?
>>
>> Hmmm, they must have a warehouse the size of the earth to stock all the
>> different values.
>
>In practice, quite good results would be had with 1% resistors (i.e., power 
>matching to 2%, SWR < 1.01).  I didn't bother truncating the decimals, it 
>looks more impressive that way. ;-D
>
>You might not even get 1% values in power resistors (say for a 100W+ 
>version), necessitating some stacking of series and parallel values to get 
>acceptable accuracy.
>
>Likely, quite a good tradeoff (better than 10%) can be found just by playing 
>around with the set of nearest E6 values.
>
>I wonder how much effect the physical length of the resistor will have.  At 
>frequencies where the resistor itself is 1/4 wavelength long, the 
>transmission line length has the effect of 1/4-wave-transformering half of 
>the resistor from a series equivalent to a parallel equivalent, or vice 
>versa.  The effect is higher loss per resistor.  The SWR should change 
>slightly at very high frequencies, but more importantly, the power gets 
>concentrated towards the beginning of the network, reducing its ultimate 
>power limit.  (Skin effect will behave similarly, too.)
>
>Resistors with high impedances (aka inductive wirewound resistors) would 
>also be problematic for the series resistors, but not necessarily a big 
>issue for the early parallel resistors (which may have values on par with 
>their AC impedances).  As the series and parallel values both converge 
>towards 50 ohms, the characteristic impedance should converge as well, 
>making bulk film parts more desirable than wound or sinuous-path-etched 
>parts.
>
>Tim

The ultimate wideband power attenuator might be a sheet of resistance
material over a substrate, a distributed-lossy microstrip structure.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453603

"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
news:lk6ddclvor5p8rpfe56e9k22rn2cbgt215@4ax.com...
> The ultimate wideband power attenuator might be a sheet of resistance
> material over a substrate, a distributed-lossy microstrip structure.

Or even better, one with tapered resistivity, so it's got lower losses where 
there's the most power, and so on.

A spool of RG-58 is a pretty good resistor, if a nonuniform one.  It's been 
done before.

After a hundred feet or so, you wouldn't even much care about a wirewound 
resistor as the final termination!

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#453607

On Sat, 25 Mar 2017 15:32:24 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
>news:lk6ddclvor5p8rpfe56e9k22rn2cbgt215@4ax.com...
>> The ultimate wideband power attenuator might be a sheet of resistance
>> material over a substrate, a distributed-lossy microstrip structure.
>
>Or even better, one with tapered resistivity, so it's got lower losses where 
>there's the most power, and so on.
>
>A spool of RG-58 is a pretty good resistor, if a nonuniform one.  It's been 
>done before.
>
>After a hundred feet or so, you wouldn't even much care about a wirewound 
>resistor as the final termination!
>
>Tim

You could short it after it accumulates 50 ohms of resistance.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453610

On 03/25/2017 04:54 PM, John Larkin wrote:
> On Sat, 25 Mar 2017 15:32:24 -0500, "Tim Williams"
> <tiwill@seventransistorlabs.com> wrote:
>
>> "John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
>> news:lk6ddclvor5p8rpfe56e9k22rn2cbgt215@4ax.com...
>>> The ultimate wideband power attenuator might be a sheet of resistance
>>> material over a substrate, a distributed-lossy microstrip structure.
>>
>> Or even better, one with tapered resistivity, so it's got lower losses where
>> there's the most power, and so on.
>>
>> A spool of RG-58 is a pretty good resistor, if a nonuniform one.  It's been
>> done before.
>>
>> After a hundred feet or so, you wouldn't even much care about a wirewound
>> resistor as the final termination!
>>
>> Tim
>
> You could short it after it accumulates 50 ohms of resistance.
>
>

Say! Need some RG-58 or RG-59 male crimp-on connectors by any chance? I 
seem to have acquired a ton of them...

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#453715

"bitrex" <bitrex@de.lete.earthlink.net> wrote in message 
news:4gBBA.151882$561.130433@fx42.iad...
> Say! Need some RG-58 or RG-59 male crimp-on connectors by any chance? I 
> seem to have acquired a ton of them...

Huh, do they come with a free crimp tool?  That's not something I do much 
of...

..Speaking of, if they were the threaded-plug kind, I could use 'em without 
crimping... should get some maybe.  Hmm...

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#453766

On 03/26/2017 03:51 AM, Tim Williams wrote:
> "bitrex" <bitrex@de.lete.earthlink.net> wrote in message
> news:4gBBA.151882$561.130433@fx42.iad...
>> Say! Need some RG-58 or RG-59 male crimp-on connectors by any chance?
>> I seem to have acquired a ton of them...
>
> Huh, do they come with a free crimp tool?  That's not something I do
> much of...
>
> ..Speaking of, if they were the threaded-plug kind, I could use 'em
> without crimping... should get some maybe.  Hmm...
>
> Tim
>

Radio Shack near me was closing, this one seemed to still have a large 
selection of DIY stuff, so I bought out a fair amount of their stock of 
the connector/mechanical stuff at fire-sale prices.

I can send you at least 4 of these pretty nice RG-58 male BNC twist-ons 
for $10 shipping included:

<https://www.dropbox.com/s/ag7epy7ijh88kvj/Photo%20Mar%2026%2C%2011%2033%2056%20AM.jpg?dl=0>

I can probably get more.

6 pack of RG-59 compression connectors like this I'll do for $6 shipping 
included. Heavy-duty nickel-plated brass with gold contacts!

<https://www.dropbox.com/s/34dt7b7711xnfx8/Photo%20Mar%2026%2C%2011%2048%2029%20AM.jpg?dl=0>

not the China garbage like this! ;-)

<http://www.ebay.com/itm/5-Pcs-BNC-Male-Compression-Adapter-To-Coaxial-Video-RG59-Cable-CCTV-Camers-/282394156723?hash=item41c000deb3:g:mKsAAOSwAKxWVnJ7>

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#453622

On Saturday, March 25, 2017 at 1:54:13 PM UTC-7, John Larkin wrote:
> On Sat, 25 Mar 2017 15:32:24 -0500, "Tim Williams"
> <tiwill@seventransistorlabs.com> wrote:
> 
> >"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
> >news:lk6ddclvor5p8rpfe56e9k22rn2cbgt215@4ax.com...
> >> The ultimate wideband power attenuato...

> >A spool of RG-58 is a pretty good resistor, if a nonuniform one.  It's been 
> >done before.
> >
> >After a hundred feet or so, you wouldn't even much care about a wirewound 
> >resistor as the final termination!

> You could short it after it accumulates 50 ohms of resistance.

That would give the solution away to the first TDR anyone applies: better
to use a 50 ohm load, even if it's nonideal.

I've always been rather fond of those controlled-impedance attenuators, that
just have a half dozen '3dB' switches.

<https://www.bmisurplus.com/products/pv255-kay-electric-co.-20-0-attenuator>

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