andy_c said:Well, many RCAs have 75 Ohm characteristic impedance. But probably not most of the "audiophile grade" ones
Well save for the oddball types like the Eichmann's, they all share the same basic coaxial geometry so they can be compatable with other RCAs and if I'm not mistaken, that geometry doesn't result in a 75 ohm impedance. Though I was only being facetious and don't think even the worst case RCA would be so far from 75 ohms it'd be worth losing any sleep over.
Though one problem with this approach is that you're stuck using 75 ohm coax cable.
se
Re: Facetious F
God I HATE those things. Especially when you're trying to get them threaded inside those tiny recessed panels on the back of your typical VCR.
And while I'm at it, who was the penny-pinching moron who came up with the idea to mold the lettering into the plastic, leave it all black and then to add insult to injury, recess it so it's virtually always in the shadows?
se
Da5id4Vz said:
God I HATE those things. Especially when you're trying to get them threaded inside those tiny recessed panels on the back of your typical VCR.
And while I'm at it, who was the penny-pinching moron who came up with the idea to mold the lettering into the plastic, leave it all black and then to add insult to injury, recess it so it's virtually always in the shadows?
se
"This statement, while inconsistent with the Whitlock reference, is consistent with the Capgo reference. And if noise induced by varying magnetic fields is ALWAYS induced differentially, then keeping conductors equidistant from the source cannot help. Only keeping the loop area as small as possible can help. And twisting does that by alternately flipping the loop with respect to the source.
The parameters of frequency of disturbances (wavelenths thereof) and pitch (twisting cycle length) are being ignored.
These influence the coupling into the line and radiated emission from the line.
Cat-6 is highly twisted for these reasons.
Eric.
Sy, my suggestion that SE go and do further research is a costructive and sincere one.
At present SE's quandry is about two particular references differing, and no alternative references cited by him.
Further research would clarify the situation for him, and us all.
The parameters of frequency of disturbances (wavelenths thereof) and pitch (twisting cycle length) are being ignored.
These influence the coupling into the line and radiated emission from the line.
Cat-6 is highly twisted for these reasons.
Eric.
Sy, my suggestion that SE go and do further research is a costructive and sincere one.
At present SE's quandry is about two particular references differing, and no alternative references cited by him.
Further research would clarify the situation for him, and us all.
Steve Eddy said:(...)Though I was only being facetious and don't think even the worst case RCA would be so far from 75 ohms it'd be worth losing any sleep over.
Though one problem with this approach is that you're stuck using 75 ohm coax cable.
Well, I was thinking about the possibility of a resonance like what's shown in the graph, which could end up in the AM radio band, causing pickup. I don't mind the 75 Ohm cable at all. The Belden 89259, though a little bulky, is very flexible and soft - not at all like the stiff RG/59 solid core. It's very reasonably priced too. And teflon has ultra-low dielectric absorption.
mrfeedback said:
Sure, but how does that make the Whitlock reference any more correct?
I have been doing further research. And that further research indicates that the Whitlock reference is in error and that the Capgo reference is correct. And that while I started out questioning the "statement in question" about noise being induced only differentially, I now find myself agreeing with it.
Want an alternative reference? Here you go: Faraday's Law
Explain to me how any conductive loop with each half being equidistant from the source of a changing magnetic field can result in a voltage of equal magnitude and polarity across each of the conductors making up that loop (i.e. common-mode) as the Whitlock reference claims.
se
Hey sully, I need a clarification here, otherwise I might be back to square one.
Previously you said:
On the left...any magnetic flux trapped within the loop...if it changes, there is a voltage generated around that loop, which shows up as a voltage between a and b at the receiver. That voltage is related to the total (integrated) amound of changing flux within that loop...
Now, I can see that if you're running a current through the loop that the flux within the loop will be a function of the current through the loop.
But when we're looking at the loop from the perspective of it being within the field of an external field source, wouldn't the induced voltage in the loop only be due to the flux that's actually cutting through the conductors?
For example, how would the flux as represented by D and E in the image below possibly result in any induced voltage in the conductors? Wouldn't the induced voltage only be a function of the flux represented by A, B, C and F, G, H?
se
Previously you said:
On the left...any magnetic flux trapped within the loop...if it changes, there is a voltage generated around that loop, which shows up as a voltage between a and b at the receiver. That voltage is related to the total (integrated) amound of changing flux within that loop...
Now, I can see that if you're running a current through the loop that the flux within the loop will be a function of the current through the loop.
But when we're looking at the loop from the perspective of it being within the field of an external field source, wouldn't the induced voltage in the loop only be due to the flux that's actually cutting through the conductors?
For example, how would the flux as represented by D and E in the image below possibly result in any induced voltage in the conductors? Wouldn't the induced voltage only be a function of the flux represented by A, B, C and F, G, H?
se
Don't get me started.......
How many times do I have to say this?
There is no such thing as a 75 ohm RCA connector.
Type F connectors are not designed for repeated insertion cycles.
Quantum mechanics??? 75 ohm BNCs???????? What the hell does any of this crap have to do with the original question??
About as much as the Curse of the Bambino......which lives on.
Jocko
How many times do I have to say this?
There is no such thing as a 75 ohm RCA connector.
Type F connectors are not designed for repeated insertion cycles.
Quantum mechanics??? 75 ohm BNCs???????? What the hell does any of this crap have to do with the original question??
About as much as the Curse of the Bambino......which lives on.
Jocko
No time for the old in out, just here to read the VSWR
"Well save for the oddball types like the Eichmann's, they all share the same basic coaxial geometry so they can be compatable with other RCAs and if I'm not mistaken, that geometry doesn't result in a 75 ohm impedance."
Correct! Also worth note is that the female RCA connector furthers this coax section impedance mismatch. This is even true for the Eichmann Bullet Plug male RCA after it is inserted into the female RCA. This impedance mismatch is really only an issue
with digital and to a lesser extent video cables. There is a nulling circuit that can compensate for this in a large degree with a very small and simple network that fits easily inside the male RCA.
"Well save for the oddball types like the Eichmann's, they all share the same basic coaxial geometry so they can be compatable with other RCAs and if I'm not mistaken, that geometry doesn't result in a 75 ohm impedance."
Correct! Also worth note is that the female RCA connector furthers this coax section impedance mismatch. This is even true for the Eichmann Bullet Plug male RCA after it is inserted into the female RCA. This impedance mismatch is really only an issue
with digital and to a lesser extent video cables. There is a nulling circuit that can compensate for this in a large degree with a very small and simple network that fits easily inside the male RCA.
I guess I'm still lost on why I should care about my cable's behavior at multimegahertz when I'm trying to pass a signal that's been band-limited to something like 22kHz. I'm not trying to work 40 meters, I'm trying to send low voltage musical signals with orders of magnitude longer wavelengths down a pretty short line.
Steve: There are a variety of models that don't violate Pauli (indistinguishable and nondegenerate particles). The devil comes in the choice of potential fields.
Steve: There are a variety of models that don't violate Pauli (indistinguishable and nondegenerate particles). The devil comes in the choice of potential fields.
Steve Eddy said:
What image below? are you missing it, or are you talking about somewhere else..
The induced voltage in the loop is caused by the change of flux which goes through the loop, not by the flux lines cutting through the conductors.
If the conductor moves through the flux lines, then, yes, the voltage will be proportional to the amount of flux lines the conductor is cutting through (assuming the other side of the loop is ramaining stationary). It's the rate of change of the total flux lines within a loop that causes voltage. It can get confusing when the flux being discussed is time varying.
Cheers, John
ps...clock's tickin, dude..goin radio silent in 6 hours..gonna love it..
<==that's me, tannin on da beach...
sully said:
Oops. See below.
Ok, that's what's confusing me here.
Let's say we have a loop of wire around a tube that's a perfect magnetic shield. Now change the flux within that tube. If the induced voltage has nothing to do with the flux that's cutting through the conductor making up the loop, then there would be an induced voltage in the loop even in this situation. Yes?
Yes. And I don't understand how there can be any force acting on the electrons within the conductor without their being any flux within that condoctur.
ps...clock's tickin, dude..goin radio silent in 6 hours..gonna love it..
Bah! I hope you get eaten alive by sand crabs!
Have a great and safe trip, John!
se
Now confused ...
quote:
The induced voltage in the loop is caused by the change of flux which goes through the loop, not by the flux lines cutting through the conductors.
I understood (quite possibly wrongly!) that the only way 'flux' could get inside the loop was by crossing it's boundary ? Again, I thought that this was also the case for a time varying 'flux', ie it crosses in, then out, then in etc etc.
Dave
quote:
The induced voltage in the loop is caused by the change of flux which goes through the loop, not by the flux lines cutting through the conductors.
I understood (quite possibly wrongly!) that the only way 'flux' could get inside the loop was by crossing it's boundary ? Again, I thought that this was also the case for a time varying 'flux', ie it crosses in, then out, then in etc etc.
Dave
Steve Eddy said:
Let's say we have a loop of wire around a tube that's a perfect magnetic shield. Now change the flux within that tube. If the induced voltage has nothing to do with the flux that's cutting through the conductor making up the loop, then there would be an induced voltage in the loop even in this situation. Yes?
Yes. And I don't understand how there can be any force acting on the electrons within the conductor without their being any flux within that condoctur.
Bah! I hope you get eaten alive by sand crabs!
Have a great and safe trip, John!
se
To shield, the perfect tube would have to be toroidal, so you are now talking about a toroid encasing the flux, and the wire as a single turn around a toroidal "transformer core". To be a perfect magnetic shield, the tube would be superconducting..And, a superconductor, in response to magnetic fields, generates loop currents on the surface, with current density Jc.. So, is it possible to confine a loop of flux without externally knowing it's there? I think the eaction loops of the super will give it away...after all, there is no free lunch..
As to electrons moving without the flux touching them? Don't forget, to generate the emf around the conductor loop, the field lines have to cross the conductor..that is how the total flux within the loop changes..hence, it isn't a non contact issue, the flux lines cross the conductor to force the emf.
Thanks..I will have both..
Re: Now confused ...
You understand correctly..what I mean is that the fact that the wire is in the middle of the flux lines does not mean an emf is produced. The wording of cutting by steve I took to mean going through, as in flux static w/r to wires.. but cutting can also mean "crossing". so, you are correct..
Cheers, John
DRC said:
You understand correctly..what I mean is that the fact that the wire is in the middle of the flux lines does not mean an emf is produced. The wording of cutting by steve I took to mean going through, as in flux static w/r to wires.. but cutting can also mean "crossing". so, you are correct..
Cheers, John
Re: Now confused ...
Now THAT makes sense to me.
Perhaps we're both wrong but I just couldn't get my brain wrapped around the notion that the induced voltage had nothing to do with the flux cutting through the conductors but only the flux within the loop.
What you seem to be saying here is that it is the flux that's cutting through the conductors, but since it must cut through the conductors to get inside the loop, the change of flux cutting through the conductors is equal to the change of flux within the loop.
We on the same page here?
se
DRC said:
Now THAT makes sense to me.
Perhaps we're both wrong but I just couldn't get my brain wrapped around the notion that the induced voltage had nothing to do with the flux cutting through the conductors but only the flux within the loop.
What you seem to be saying here is that it is the flux that's cutting through the conductors, but since it must cut through the conductors to get inside the loop, the change of flux cutting through the conductors is equal to the change of flux within the loop.
We on the same page here?
se
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