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Re: Coaxial cable calculation

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On 4/11/2018 8:39 AM, Sergio wrote:
> On 4/11/2018 6:23 AM, benj wrote:
>> On 4/10/2018 6:18 PM, Sergio wrote:
>>> On 4/10/2018 3:03 PM, benj wrote:
>>>> On 4/10/2018 12:44 PM, Sergio wrote:
>>>>> On 4/10/2018 11:32 AM, Lofty Goat wrote:
>>>>>> On Tue, 10 Apr 2018 18:21:42 +0200 (GMT+02:00), Libor Striz
>>>>>> <poutnik4REMOVEnntp@CAPITALSgmail.com> wrote:
>>>>>>
>>>>>>> Sergio <invalid@invalid.com> Wrote in message:
>>>>>>>> On 4/10/2018 1:42 AM, Trevor Wilson wrote:
>>>>>>>>> Here's a question that stumped me back in the old slide rule days:
>>>>>>>>>
>>>>>>>>> A coaxial cable, having an inner diameter of 0.0254mm (0.001") and
>>>>>>>>> using
>>>>>>>>> an insulator with a dielectric constant of 2.56, is yo have a
>>>>>>>>> characteristic impedance of 2,000 Ohms. What must be the outer
>>>>>>>>> conductor
>>>>>>>>> diameter?
>>>>>>>>>
>>>>>>>>> You guys can locate the appropriate method of calculation.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> your question is malformed.
>>>>>>>>
>>>>>>>>    what is yo ?   don't  you mean Zo, which is normally used for
>>>>>>>> characteristic impedance of coaxial cables ?
>>>>>>>>
>>>>>>>> what frequency or frequency band ?
>>>>>>>>
>>>>>>>>
>>>>>>> Yo must mean you...
>>>>>>
>>>>>> Arcane symbol for admittance, the reciprocal of impedance.  Modern
>>>>>> texts
>>>>>> use sigma instead.
>>>>>>
>>>>>
>>>>> double checking, usually that is Yo, and measured in siemens, not ohms.
>>>>>
>>>>> so still need a clarification Trevor, do you mean Yo 2000 siemens or Zo
>>>>> 2000 Ohms ?
>>>>>
>>>>> and frequency band too, (there are places coax won't work)
>>>>>
>>>> Look at the science deniers squirm as they try to deny this typo!
>>>> Clearly Yo is NOT admittance, since Trevor himself say "is yo have a
>>>> characteristic impedance of 2,000 Ohms" He clearly used the word
>>>> "impedance" not "admittance". Anyway if anyone here knew any actual
>>>> practical science you'd know that a Zo of 1/2000 ohms gives a coax of
>>>> ridiculous dimensions. Won't find one on your TV I'm sure.
>>>>
>>>> TREVOR MADE A TYPO and that proves he's uneducated, ignorant and insane!
>>>> Neener, Neener, Neener!
>>>>
>>>
>>> Initially I thought he meant "yo" like the urban "you", but that would
>>> be a misspelling, and he would not recognize a misspelled word.
>>>
>>> at least he posted some physics/science stuff in here, so He gets a B.
>>
>> Actually I smell engineering rather than science. I say C.
>> For some reason engineers like to hang in Sci.physics pretending they
>> are physicists arguing science.
>>
>>> also, when did calculators replace slide rules, in college ?
>>
>> Of course in the old days the way to demonstrate that you were nerdy
>> beyond all belief was to have a slide rule case dangling from your belt
>> in college. EeeW! Was like the coloring of a poisonous snake telling all
>> hawt babes "don't touch"...unless you were there to bag a nerd with
>> decent earning potential once graduated. But then came the HP35 and
>> while Old man Hewlett insisted it fit a shirt pocket (actually was too
>> long to fit nicely) suddenly the proper way to show nerdy class was now
>> to have the leather HP35 pouch dangling from your belt. Given the price
>> it did dual duty as a badge of nerdyness AND potential earning capacity.
>>
>>> Extra Credit Question: anyone know what the term "lizard" means on
>>> campus ? (think way-way back)
>>
> 
> 
> yep, the engineers had Tails, the slide rule cases hanging off their belts.
> 

Zo = (L/C)^(0.5) = 138*log(D/d)/((ur*er)^0.5


Solve for D

D = d * 10^(Zo * )(ur*er)^0.5) /138)

ur typically 1 = relative permeability

D= 0.001 * 10^ (2000* ((1*2.56)^0.5) /138) = 0.001 * 10^23 = 10^20

       which says Zo is too big, probably a typo, extra 0.


take a max sized coax where D/d is 100

Zo = 138*2/1.6 = 172 ohms

   Super max D/d = 1000

Zo = 138*3/1.6 = 258

so a Zo of greater than 250 is becoming unrealizable, inner conductor
fried by power levels, too much plastic, cable too fat

and this degenerates into single wire impeadance, OR circular waveguide,
as you remove outer shield or inner wire, and you can leave the plastic
on, or remove it, and that depends upon frequency

the above #'s were not generated with a slide rule, could not find the
batteries.

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Thread

Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-10 16:42 +1000
  Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 05:20 -0400
    Re: Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-10 19:33 +1000
      Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 15:28 -0400
        Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-11 08:36 -0500
          Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-11 14:38 -0400
            Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-11 13:55 -0500
      Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 15:45 -0400
    Re: Coaxial cable calculation Libor Striz <poutnik4REMOVEnntp@CAPITALSgmail.com> - 2018-04-10 12:24 +0200
      Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 15:37 -0400
  Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-10 10:59 -0500
    Re: Coaxial cable calculation Libor Striz <poutnik4REMOVEnntp@CAPITALSgmail.com> - 2018-04-10 18:21 +0200
      Re: Coaxial cable calculation Lofty Goat <rlwatkins@gmail.com> - 2018-04-10 11:32 -0500
        Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-10 11:44 -0500
          Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 16:03 -0400
            Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-10 17:18 -0500
              Re: Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-11 08:24 +1000
                Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-10 17:38 -0500
                Re: Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-11 08:42 +1000
                Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-11 07:36 -0400
                Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-11 08:38 -0500
                Re: Coaxial cable calculation Lofty Goat <rlwatkins@gmail.com> - 2018-04-11 21:57 -0500
              Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-11 07:23 -0400
                Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-11 08:39 -0500
                Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-11 11:20 -0500
    Re: Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-11 05:48 +1000
      Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 16:10 -0400
      Re: Coaxial cable calculation Sergio <invalid@invalid.com> - 2018-04-10 17:30 -0500
      Re: Coaxial cable calculation Lofty Goat <rlwatkins@gmail.com> - 2018-04-11 21:57 -0500
    Re: Coaxial cable calculation benj <benj@nobody.net> - 2018-04-10 15:54 -0400
      Re: Coaxial cable calculation Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> - 2018-04-11 06:01 +1000

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