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slightly off topic feel free to delete

Mikek All Messages By This Member #1598 > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek .
Tom Lee All Messages By This Member #1599 开云体育 If you take random hookup wire and twist it with some random pitch, you'll often see something closer to 100 than to 150, but 150 is certainly not out of the question. That said, CAT5 is spec'd at 100 ohms, plus or minus 5 ohms. -- Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 3/29/2023 08:51, Mikek wrote: toggle quoted message Show quoted text > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek .
Tom Lee All Messages By This Member #1600 开云体育 And I should have added that the impedance is measured at a frequency of 100MHz. -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 3/29/2023 09:14, Tom Lee wrote: toggle quoted message Show quoted text If you take random hookup wire and twist it with some random pitch, you'll often see something closer to 100 than to 150, but 150 is certainly not out of the question. That said, CAT5 is spec'd at 100 ohms, plus or minus 5 ohms. -- Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 3/29/2023 08:51, Mikek wrote: > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek .
Michael A. Terrell All Messages By This Member #1601 USTP works, but not a good idea in areas with a lot of lightning strikes. Back in the '80s I maintained a 36 channel Cable TV headend. One strike blew out 12 audio inputs on the modulators, and caused distortion in a few more. I replaced the cables with single pair shielded audio cable and never lost another CA3240 FET input op amp afterwards.
si_emi_01 All Messages By This Member #1604 开云体育 To add to this… ? The number of twists per foot determines the differential-mode susceptibility of the cable. More twists per foot, higher rejection of differential energy. ? It does not improve the Common Mode environment susceptibility though – the cable is still a monopole receive or transmit antenna. ? Shielding and properly terminating the shields helps with Common-mode susceptibility and emissions. ? Ross ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Tom Lee Sent: Wednesday, March 29, 2023 10:16 AM To: [email protected] Subject: Re: [Test Equipment Design & Construction] slightly off topic feel free to delete ? And I should have added that the impedance is measured at a frequency of 100MHz. -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 3/29/2023 09:14, Tom Lee wrote: If you take random hookup wire and twist it with some random pitch, you'll often see something closer to 100 than to 150, but 150 is certainly not out of the question. That said, CAT5 is spec'd at 100 ohms, plus or minus 5 ohms. -- Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 3/29/2023 08:51, Mikek wrote: > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek . ? ?
John Kolb All Messages By This Member #1605 开云体育 The impedance can vary with the number of turns per distance. "The characteristic impedance of a transmission line is determined by its physical parameters, such as the diameter of the conductors, the spacing between them, and the dielectric material between them. Twisting the conductors of a transmission line changes these physical parameters and can alter the characteristic impedance. When the number of turns per unit distance is increased, the capacitance between the conductors decreases, and the inductance increases. This change in capacitance and inductance can cause the characteristic impedance to change."??? chatGPT When I worked at Southcom International, the engineer had a chart for 28 and 30 ga wire with Z vs turns per inch. John ?? KK6IL On 3/29/2023 8:51 AM, Mikek wrote: toggle quoted message Show quoted text > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek .
Leon Robinson All Messages By This Member #1606 The statement that capacitance decreases as the turns per unit increases is wrong, the capacitance will INCREASE.? Don't believe everything that an AI claims. Leon Robinson ?? K5JLR Political Correctness is a Political Disease. Politicians and Diapers should be changed often and for the same reasons. On Wednesday, March 29, 2023 at 06:18:18 PM CDT, John Kolb <jlkolb@...> wrote: The impedance can vary with the number of turns per distance. "The characteristic impedance of a transmission line is determined by its physical parameters, such as the diameter of the conductors, the spacing between them, and the dielectric material between them. Twisting the conductors of a transmission line changes these physical parameters and can alter the characteristic impedance. When the number of turns per unit distance is increased, the capacitance between the conductors decreases, and the inductance increases. This change in capacitance and inductance can cause the characteristic impedance to change."??? chatGPT When I worked at Southcom International, the engineer had a chart for 28 and 30 ga wire with Z vs turns per inch. John ?? KK6IL On 3/29/2023 8:51 AM, Mikek wrote: > unshielded twisted pair ethernet cables: > I think the nominal impedance is 150 ohms ?I think twisted pairs are closer to 100Ω, I once measured one and got 102Ω. It is dependent in the diameter of the wire and the thickness of the insulation. Using the calculator,? I get a slight lower number for a Cat5 wire I have, it is 24 gauge with polyethylene? insulation that is 0.075" thick. This puts the 0.0201" wire spaced 0.015" by the insulation that has an er of 2.25 at a center to center distance of 0.035" and an impedance of 92Ω. ?If the spacing of the center to center distance is increased 0.003" the impedance becomes 100Ω. Or if the er is lowered to 1.9 the impedance is 100Ω. i.e. I could have a little error in the thickness and/or the er of the insulation, a small change could get me close to 100Ω. ????????????????????????????? Mikek .
Mikek All Messages By This Member #1608 Hi Michael, ?What you say about your experience may be be true, on the other hand I have had a 250ft length of CAT5 feeding my Icom R-71a for about 10 years, in Florida, and so far all is good. Plenty of people with coax antenna leads have had their radios damaged by lightning, ?Lightning is like water, "water always wins, just look at the Grand Canyon". :-) ?????????????????????????????????????????? Mikek ?PS. miss you over on SED.

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