Cable capacitance: a small demonstration of the effects
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- Опубліковано 11 вер 2024
- A small video about the so called “cable capacitance”.
Everywhere where copper or metal cables with 2 or more wires inside (be it the “mantle” and the central wire, say: coax cable) are used to transport signals (be it audio or HF) there is “cable capacitance” that presses down e.g. possibilities to transport audio frequencies over (very) long wires, say: 20 KHz-500 KHz, say over kilometers of 2 pole wires.
Or: even a 1 pole wire, when the other signal transport wire is immersed in the “ground”, so “the earth” is used as "wire", shows that property.
Such a solution (1 wire earthed) also has a cable capacitance that influences its performance.
But of course the “cable capacitance problem” was already properly solved in the 1950’s by cable (telephone) companies like General Electric (US) and others, and also by Philips (Netherlands) with their sophisticated systems of “line telephony,” where hundreds of telephone users could use only one telephone line, by the use of “pupin” coils, electronic circuits that “fractioned” (in a circular way=switched in a sequence) the line use via (say) a 50 KHz mode, using line amplifiers etc.
This video only demonstrates the effect of cable capacitance. Everyone can conclude what kind of effects this capacitance can have.
In general: for audio and telephone applications a damping of the high frequencies in the audio band (say: 10 KHz - 20 KHz).
By the way: the issue of coax cables in HF applications (radio transmitters and radio receivers) is an essential other issue, not discussed here.
I don’t know much about the use of coax cables, apart of the things that everyone knows: how to use and apply them and split them with the help of resistors to TV receivers, SAT receivers, in a household etc, keeping their impedance (often) on “75 Ohm”.
This video (thus) is only about (stray) capacitance between 2 electrodes in a wire.
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Oscillating audio amplifiers on long wiring to loudspeakers?
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Nice demonstration.
By the way, in english, the outside braid on coax cable is called shielding.
Thanks for the video, have a great weekend.
Thanks for your comment.
Very interesting KO...Thank You!
Thanks, good to hear that.
Thank you ! This was helpful .
Thanks, good to hear that.
good demonstration.
Thanks, good to hear that you liked it and it was worthfull.
Thank you for the demonstration. What about the capacitance in a single leader. From start to end. Such capacitance in serie with signal will become a high pass filter together with the input impedance (which is parallel) in next amplifying stage. say between a preamp and a power amp. Will such capacitance exist?
yes
How is this effect in the GHz range? As a thought experiment (only High School-level physics experience) I’m wondering what the best kind of electrical cable (“no matter the cost”) would be to use for PCI Express (Gen4) signals that use as far as I know 8 GHz signals for let’s say 0.5 m length. There are SFF cables for PCI Gen4 (OCuLink and SlimSAS HD connectors for example) but there are really EXTREME quality control issues :(
Thanks for your reaction. Sorry I canot advise you, because the GHZ range is beyond the scope of my knowledge and experiments. My video is/was more or less "educational" to show some basic effects of cable impedance/capacitance. It is a sea to drink, even in the (say) 50 KC-500 KC range, like old telephone cables that were layed down in the oceans, say 80-100 years ago. They used "pupin" coils + special amplifiers to transport the signals properly. Perhaps you can find info via radio amateurs. 13 march 2022.
because the long cable is coiled up, it will also act as an inductor, removing some high frequency. what would happen if the long cable was stretched out, or twisted together (like cat5 twisted pair)?
interesting video nonetheless, thank you!
Thanks and yes, surely it acts as an inductor.
Surely wire capacitance in speaker wires and even in relatively short interconnect wires has an audible effect.
your right it would certainly have an effect but the question is would it be enough of an effect to be detectable to the human ear and therefore a problem (I seriously dont think that it would be) its all relative....
@@T2D.SteveArcs You pinpointed it. That is, indeed, the issue and the human ear has many (read: many....) and different (read: different) properties when "receiving" a sound, say: an atmospheric sound wave between (say) 5 Hertz and 20 KHz. We need a book to explain that.
@@radiofun232 Yes that is very true KO
The capacitance along with its inductance is what determines its 75ohm impedance...
I never understood that...
@@radiofun232 Hi Ko what do you mean you never understood what? please explain
@@T2D.SteveArcs Simply: what means 75 Ohm in a HF cable?
@@radiofun232 sorry Ko i simply mean that 75ohm coax is so called 75ohm coax due to its characteristic impedance which is due to the relationship of the capacitance and inductance of the conductors in an infinitely long transmission line or one terminated in its own characteristic impedance (without reflections) hope this helps thanks
you can find the impedance of a coax (transmission line) by connecting one end of line in question to your signal generator (and T off to scope) and connect a potentiometer to the other end of the line then launch a hf square wave into the line while observing the waveform on the scope.. Then adjust the pot until you have a decent looking signal (no reflections) then de-solder pot and measure its value and that should give you the characteristic impedance of the line ie 50ohm - 75ohm 150ohm etc
There is effect on cars they like engine run on expecialy capacitors have effects on generators ore starter motors ore ignition coil similarity to static nothing realy good but usefull for plazma and amplifiers probably
I am interested: what do you mean?
@@radiofun232 Im meaning they have effects on evry electric devices alternator exampel gives ore reduces amps volts ore changes starting charge rpm if you use centrain capacitors ore frequency .
Starter motor acts slow with masive torque giving hidrolic lock to compresion stroke to warm up engine forcefully with out fuel just shear piston preshure ore inurt gases when ready just reverse ore use capacitor to over spin the starter with higher voltage in fraction of second engine shuld turn on carburetors you remove choke and use only gas flap and it must by fully closed when you want to turn engine over just similate choke with foot gas pedal for ignition coil you can get ither plazma ore amplifier by useing diferent capacitor values I normaly use hv ceramic capacitor and put that thing any where on ignition coil positive lead and other side of capacitor to ground you get plazma ore use starter selenoid as amplifier on start up ore remove starter selenoid R terminal type and use it as amplifier all the time with ignition coil use liqued cooled ignition coils ore high perfomance parts .
Well lot effects acure not just these.
Basicaly your whole wire harnest get effected.
In my case evry thing worked faster baterry charge was some where around 15_16v .
Only trobel I hade culd not figure out how to modify my alternator starting charge rpm it gone from 1k rpm up to 2 -2,5k rpm thats problem Im no real electritian know basic staff but experiment lot in the proces .
Those frequencys can by benefitial ore deadly to cars depends how you use it.
Mostly gasoline/dizel engine blocks get effected from it .
@@elvinkasumovic3296 I don't think that cable capacitances play such a big role in your case, anyway, thanks. 7 okt 2021.
@@radiofun232 well on hybrid engines and old military engines yes they play big role those are not normal engines to begin with diference in potential of any cinde is deadly to engines belive it ore not some chemical reactions like cooling system electrolisys eats away rubber seals gaskets even insulation on kabels no only you end up with dead short those are some industry secrets nearly any thing burns in car in centrain way even some rubber conducts electricity so the rule is any diference in potential will effect some thing in my case crossing wires parasitic spark burning ore piting coroding kabels melting capacitor effects with coolant electrolisys etc so actualy it is big diference expecialy for exampel if some one fumels on radio that thing is causing lot static old dc magnetos didnt have lot things 1 wire on the block evry thing works plain and simpel tuch dc lead to engine with centrain frequency ques what your engine refuse to stop ☺️ even some dizel engine use back curent to stop them mostly such cinde of problems peopel run to are GM and Chevy based cars their mostly prone to those things with shity wire harnest and blown head gasket any thing culd go wrong basicaly any way not realy much sence with your video but it describes more what capacitors can do and how wires and insulators effect nerby devices if they are to close . Include with those 2 pieces of wire salt ore acid and we will see how volta baterry look like well yeah it wuld probably bitte ya ass over ore some thing like that well yeah your body insulation wont alove harm but stick it in your mouth you will feal diferently probably those 2 pieces of wire culd kill you so dont try it Im just makeing exampels with no real meaning behinde it .