low MHz connector design consultant
in [Design]
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From: Baron on 2 May 2010 15:52 tm Inscribed thus: > > "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message > news:hrk0qi$1f2$1(a)news.eternal-september.org... >> tm Inscribed thus: >> >>> >>> "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message >>> news:hri41l$ple$2(a)news.eternal-september.org... >>>> tm Inscribed thus: >>>> >>>>> >>>>> "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message >>>>> news:hri2ce$910$1(a)news.eternal-september.org... >>>>>> mpm Inscribed thus: >>>>>> >>>>>>> On Apr 30, 10:58 pm, "k...(a)att.bizzzzzzzzzzzz" >>>>>> >>>>>> For co-axial cables its a function of the ratio of the diameters >>>>>> of the conductors modified by the dielectric constant of the >>>>>> insulator, or for twin conductor the spacing between them and the >>>>>> dielectric constant of the insulator. >>>>>> ie (impedance = (138 / e^(1/2)) * log (D/d)) >>>>>> >>>>> >>>>> >>>>> It also assumes a match at both ends of the line. >>>>> >>>>> >>>>> Tom >>>> >>>> ??? >>> >>> Sure. Take a piece of coax, any impedance, 1/4 wavelength long, and >>> short one end. What do you see at the other end? >>> >>> Now match both ends. What impedance do you see at any point of the >>> line? >>> >>> >>> >>> >>> Tom >> >> That has absolutely nothing to do with characteristic impedance ! >> > Hi Baron, > > I never said it did. Just that matching the characteristic impedance > on each end of the line is necessary for the full transfer of power. Yes ! Matching is a requirement for efficient transfer of power. > If the line is mis-matched, the impedance anywhere on the line will > be a complex function. Right? Yes I agree with you ! Since the line impedance doesn't change because of a mismatch. Its a physical characteristic of the line, so it can't change. The VSWR along the line will change with a mismatched load. So the complex impedance will be a cyclic function of line length as seen at any point on the line. > > Regards, > Tom -- Best Regards: Baron.
From: John Larkin on 2 May 2010 16:47 On Sun, 02 May 2010 20:52:45 +0100, Baron <baron.nospam(a)linuxmaniac.nospam.net> wrote: >tm Inscribed thus: > >> >> "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message >> news:hrk0qi$1f2$1(a)news.eternal-september.org... >>> tm Inscribed thus: >>> >>>> >>>> "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message >>>> news:hri41l$ple$2(a)news.eternal-september.org... >>>>> tm Inscribed thus: >>>>> >>>>>> >>>>>> "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message >>>>>> news:hri2ce$910$1(a)news.eternal-september.org... >>>>>>> mpm Inscribed thus: >>>>>>> >>>>>>>> On Apr 30, 10:58 pm, "k...(a)att.bizzzzzzzzzzzz" >>>>>>> >>>>>>> For co-axial cables its a function of the ratio of the diameters >>>>>>> of the conductors modified by the dielectric constant of the >>>>>>> insulator, or for twin conductor the spacing between them and the >>>>>>> dielectric constant of the insulator. >>>>>>> ie (impedance = (138 / e^(1/2)) * log (D/d)) >>>>>>> >>>>>> >>>>>> >>>>>> It also assumes a match at both ends of the line. >>>>>> >>>>>> >>>>>> Tom >>>>> >>>>> ??? >>>> >>>> Sure. Take a piece of coax, any impedance, 1/4 wavelength long, and >>>> short one end. What do you see at the other end? >>>> >>>> Now match both ends. What impedance do you see at any point of the >>>> line? >>>> >>>> >>>> >>>> >>>> Tom >>> >>> That has absolutely nothing to do with characteristic impedance ! >>> >> Hi Baron, >> >> I never said it did. Just that matching the characteristic impedance >> on each end of the line is necessary for the full transfer of power. > >Yes ! Matching is a requirement for efficient transfer of power. Actually, it isn't. John
From: Joerg on 2 May 2010 17:15 John Larkin wrote: > On Sun, 02 May 2010 20:52:45 +0100, Baron > <baron.nospam(a)linuxmaniac.nospam.net> wrote: > [...] >> Yes ! Matching is a requirement for efficient transfer of power. > Probably the transmitter wasn't meant here. > Actually, it isn't. > A professor of mine actually said so, that a transmitter must have an output impedance equal to the line impedance. I had to leave the auditorium to shake off a major ROFL attack. Later I told him that flames would be shooting out the buildings of large AM transmitters, and brought him a schematic. That schematic was quite sobering :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: krw on 2 May 2010 20:57 On Sat, 1 May 2010 20:45:50 -0700 (PDT), mpm <mpmillard(a)aol.com> wrote: >On May 1, 5:49�pm, "k...(a)att.bizzzzzzzzzzzz" <k...(a)att.bizzzzzzzzzzzz> >wrote: >> On Sat, 1 May 2010 12:00:27 -0700 (PDT), mpm <mpmill...(a)aol.com> wrote: >> >On May 1, 9:17�am, "k...(a)att.bizzzzzzzzzzzz" <k...(a)att.bizzzzzzzzzzzz> >> >wrote: >> >> On Sat, 1 May 2010 00:34:48 -0700 (PDT), mpm <mpmill...(a)aol.com> wrote: >> >> >On Apr 30, 10:58�pm, "k...(a)att.bizzzzzzzzzzzz" >> >> ><k...(a)att.bizzzzzzzzzzzz> wrote: >> >> >> On Fri, 30 Apr 2010 18:39:21 -0700 (PDT), mpm <mpmill...(a)aol.com> wrote: >> >> >> >On Apr 30, 4:31�pm, Wimpie <wimabc...(a)tetech.nl> wrote: >> >> >> >> On 30 abr, 13:54, "mook johnson" <m...(a)mook.net> wrote: >> >> >> >> >> > "John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in message >> >> >> >> >> >news:ql9kt5tg7s7e5q7pb460gcdig4r00jjmrj(a)4ax.com... >> >> >> >> >> > > On Thu, 29 Apr 2010 18:30:41 -0500, "mook johnson" <m...(a)mook.net> >> >> >> >> > > wrote: >> >> >> >> >> > >>Gents, >> >> >> >> >> > >>I looking for a consultant that can assist in the design of a custom >> >> >> >> > >>military style connector with controlled characteristic impedance and >> >> >> >> > >>insertion loss between two terminals in the 1MHz - 20MHz frequency range. >> >> >> >> >> > >>This connector is special because is the application so an off the shelf >> >> >> >> > >>component will not work. >> >> >> >> >> > >>Any leads where I can start looking for such a consultant? >> >> >> >> >> > >>thanks >> >> >> >> >> > > There are so many military connectors, including ones for wild >> >> >> >> > > environments, hermetic, etc, some standard part might work. >> >> >> >> >> > > 20 MHz isn't very demanding. Most any mil connector will be "matched" >> >> >> >> > > to any impedance at 20 MHz. Wavelength is 15 meters! >> >> >> >> >> > > John >> >> >> >> >> > The connector I need goes into environments that far exceed military >> >> >> >> > applications but the physical concept is similar. �We have an in-house >> >> >> >> > connector company that makes these connectors for us but they have never had >> >> >> >> > to deal with never greater than >200KHz signals before. �We tried using our >> >> >> >> > regular connectors for this application and the impedance mismatch and >> >> >> >> > insertion loss were extreme at 5 - 20MHz. �The Zo mismatched by 50% and was >> >> >> >> > not stable above 1MHz and had several resonant modes. Insertion loss >> >> >> >> > something on the order is 6dB/connector and we'll have a couple dozen in >> >> >> >> > series on this line. �The number of series connection is the is the rub and >> >> >> >> > it is unavoidable, non negotiable. >> >> >> >> >> > There are some commercial plastic connectors that tested very well (just to >> >> >> >> > validate our test setup) with good impedance match/stability (+/- 5%) and >> >> >> >> > low insertion loss (.1dB/connector) but they won't take the environment. >> >> >> >> >> > I'm looking for a consultant that can provide either of the following >> >> >> >> >> > 1) model a connector that is already designed but not made (basically review >> >> >> >> > the in-house company proposed design) and simulate the high frequency >> >> >> >> > response of the design. >> >> >> >> >> > 2) Give direction for the connector design based on constraints of material >> >> >> >> > choices, physical size and geometry to meet the desired electrical signal >> >> >> >> > characteristics while withstanding the environmental conditions. >> >> >> >> >> > The cut and try approach based on simple equations has a long cycle time. >> >> >> >> > I'm looking to improve my chances of getting it right the first time. >> >> >> >> >> Hello Mook, >> >> >> >> >> When you have already a company that knows mechanical design and >> >> >> >> reliability issues, you only need the EM-field guy. � When you can >> >> >> >> keep the mechanical guys and the EM-field guy in one room, this should >> >> >> >> converge to a solution fast. >> >> >> >> >> One familiar with the concept of characteristic impedance, complex >> >> >> >> propagation constant (contains both complex epsilon and permeability) >> >> >> >> and know how to measure the material constants can do the job. >> >> >> >> >> What about: required Return Loss, characteristic impedance, Insertion >> >> >> >> loss, propagation delay, size, �cross section, (coaxial, square, >> >> >> >> symmetrical, etc), peak and average power, etc? >> >> >> >> >> Kind regards, >> >> >> >> >> Wim >> >> >> >> PA3DJSwww.tetech.nl >> >> >> >> when you delete abc first, PM will reach me- Hide quoted text - >> >> >> >> >> - Show quoted text - >> >> >> >> >I have a question for you: >> >> >> >> >Do you believe that the characteristic impedance is dependent on the >> >> >> >length of the coax? >> >> >> >(For the ratio of transverse electric field to transverse magnetic >> >> >> >field launched on a transmission line of infinite length.) >> >> >> >> "infinite length" <> "independent of length"- Hide quoted text - >> >> >> >> - Show quoted text - >> >> >> >Not sure I understand your cryptic post. >> >> >> >That is how characteristic impedance is classically defined, and I'm >> >> >asking him if he believes that characteristic impedance is dependent >> >> >on length? >> >> >> But you talk about dependency on length and "infinite" length in the same >> >> paragraph. �You can't have both variable length (which would include short) >> >> and a dependency on being "infinite".- Hide quoted text - >> >> >> - Show quoted text - >> >> >OK - Maybe I could have stated that a little better.... �(?) >> >> >My point: �Does the length of the coax (or connector - since that's >> >the topic of this post) have anything to do with characteristic >> >impedance? >> >And NOTE THAT THE DEFINITION OF CHARACTERISTIC IMPEDANCE ITSELF >> >INCLUDES AN INFINITE LENGTH. (Which a connector DOES NOT have.) >> >> So you're asking if the characteristic impedance of a piece of coax varies >> with length, when in the same question you define "characteristic impedance" >> to be impedance (V/I) of an infinite length coax. �Kinda silly to ask a >> question when your question defines the answer, no? �Are blue birds blue? >> >> >If I ask that question without mentioning that the various equations >> >for characteristic impedance are derived from terms that include >> >inductance per unit length (even if they later cancel out), then the >> >question is absolutely meaningless. >> >> No, one assumes that the term "characteristic impedance" means something in a >> group with the name sci.electronics.design. >> >> >So, I am PURPOSELY avoiding any possibility of a circular definition >> >when I ask this question. >> >> No avoidance at all. Your question was self-circular. >> >> >Do you understand now? >> >> Why you asked the question the way you did? �No, I have no idea. >> >> >Once you understand the question, we will look at whether or not the >> >traditional equations for characteristic impedance are even valid >> >(hint: I don't think they are!), given that they do not agree when >> >applied to antennas, (which certainly have a length component). �And, >> >since they depend on antenna length, it contradicts the fundamental >> >definitions. �Even more interesting, the various calculations do not >> >yield identical results, particularly if you consider an antenna to be >> >a transmission line immersed in three-dimensional space. >> >> Perhaps the (simplified, btw) equations don't have enough terms to describe >> every possibility that you think they should cover.- Hide quoted text - >> >> - Show quoted text - > >Honestly, I don't have the desire to get into a discussion/argument >over semantics. Engineering is not semantics. >The question is phrased correctly. The statement which follows it is >also phrased correctly. No, it is not. Your question is circular; you're defining the terms, within the question, such that there is only one answer, also answered within the question. >I am traveling for a few days, so further thoughts will have to >wait.... >This may be too complicated a discussion for SED anyway. No, it really isn't that complicated. You're making it complicated.
From: krw on 2 May 2010 21:00
On Sun, 02 May 2010 09:29:10 -0700, Joerg <invalid(a)invalid.invalid> wrote: >mpm wrote: > >[...] > >> I am traveling for a few days, so further thoughts will have to >> wait.... >> This may be too complicated a discussion for SED anyway. >> > >No laptop? Most airports have free WiFi. Most? More than half the airports I've been in have access fees (as much as $10/day). Some are AT&T, so I was covered there. >Once I sat in the Irish Pub >next to gate C1 when connecting in Las Vegas. Held a pint of Guinness up >in front of the netbook, hit the snap picture button, emailed it to my >wife right from the bar stool :-) ....and then you came home to a cold bed. ;-) The interesting thing that I've found is that the higher the price of a hotel room, the lower the probability of free Internet access (also averaging about $10/day). Of course all the other hidden fees are in more or less the same proportions. |