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Hi
Why characteristic impedance of transmission line isn't important at
low frequencies (1000kHz) and it is one of the main parameters in RF?
At high frequencies if a generator isn't matched with the impedance
of the line the reflection of the power can damage the genarator, why
isn't that the case at low frequencies? Or am I wrong about the
destroying the generator?
(example: If we connect high power audio amp to speaker we don't have
to worry about the characteristic impedance of the cable) Can
somebody explain this?
Thanks
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Author: Andrew HolmeDate: 17:16 07-06-07
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<skyline1@net.hr> wrote in message
news:1181250101.107112.293380@w5g2000hsg.googlegroups.com...
> Hi
>
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz) and it is one of the main parameters in RF?
> At high frequencies if a generator isn't matched with the impedance
> of the line the reflection of the power can damage the genarator, why
> isn't that the case at low frequencies? Or am I wrong about the
> destroying the generator?
> (example: If we connect high power audio amp to speaker we don't have
> to worry about the characteristic impedance of the cable) Can
> somebody explain this?
>
>
Transmission line effects are negligible if the line length is a tiny
fraction of a wavelength.
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Author: Stanislaw FlattoDate: 17:27 07-06-07
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skyline1@net.hr wrote:
> Hi
>
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz) and it is one of the main parameters in RF?
> At high frequencies if a generator isn't matched with the impedance
> of the line the reflection of the power can damage the genarator, why
> isn't that the case at low frequencies? Or am I wrong about the
> destroying the generator?
> (example: If we connect high power audio amp to speaker we don't have
> to worry about the characteristic impedance of the cable) Can
> somebody explain this?
>
>
> Thanks
>
Totally wrong.
Just ask a 'serious' electic company engineer on matching generators to
loads with and without reflections.
It is the physics that is involved, not beliefs or frequencies.
HTH
Stanislaw
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Author: EeyoreDate: 17:52 07-06-07
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skyline1@net.hr wrote:
> Hi
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz)
Who says it isn't ? That's the upper end of the DSL frequencies on a phone line
and it's very important to use transmissin line thinking for that to work.
Graham
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Author: EeyoreDate: 17:55 07-06-07
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skyline1@net.hr wrote:
> (example: If we connect high power audio amp to speaker we don't have
> to worry about the characteristic impedance of the cable) Can
> somebody explain this?
Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km. A speaker cable is
maybe 10m. There's no transmission line effect to consider here.
In long-distance telephony, the long length of the cables make transmission line
thinking important even at these audio frequncies.
Graham
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Eeyore je napisao/la:
> skyline1@net.hr wrote:
>
> > Hi
> >
> > Why characteristic impedance of transmission line isn't important at
> > low frequencies (1000kHz)
>
> Who says it isn't ? That's the upper end of the DSL frequencies on a phone line
> and it's very important to use transmissin line thinking for that to work.
>
> Graham
Sorry, I meant to say 1000Hz not 1000kHz
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Author: Phil AllisonDate: 18:13 07-06-07
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"Andrew Holme"
>
> Transmission line effects are negligible if the line length is a tiny
> fraction of a wavelength.
>
** WRONG !!
Same old ham radio bollocks trotted out as fact about a different area of
electronics.
....... Phil
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Author: Phil AllisonDate: 18:16 07-06-07
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"Eeysore Fucking Pommy IDIOT "
>
> Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
** NOT AGAIN !!!
Can't the Graham Stevenson MORON ever get a
FUCKING decimal point right ?????
Or any other point right ??
....... Phil
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Author: Phil AllisonDate: 18:45 07-06-07
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<skyline1@net.hr>
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000Hz) and it is one of the main parameters in RF?
** That is not a correct statement - just another myth from the mouths and
keyboards of fools. All signal and power cables have a characteristic
impedance and it can matter at low frequencies.
The most important fact about characteristic impedance is that IF the load
on the end matches the cable's characteristic impedance - the parallel
capacitance & series inductance of the cable no longer has any effect.
Capacitance in a mic cable 100 metres long can have a significant effect on
the high frequency output of a mic.
The inductance of a twin wire speaker cable of only 10 metres long will
cause a drop in level at 20kHz of several dB if the load impedance is 1 ohm.
...... Phil
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Author: EeyoreDate: 19:17 07-06-07
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Phil Allison wrote:
> "Eeysore Fucking Pommy IDIOT "
> >
> > Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>
> ** NOT AGAIN !!!
>
> Can't the Graham Stevenson MORON ever get a
>
> FUCKING decimal point right ?????
>
> Or any other point right ??
It's that damn Windows calculator !
Graham
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Author: John FieldsDate: 20:08 07-06-07
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On Thu, 07 Jun 2007 23:17:06 GMT, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:
>
>
>Phil Allison wrote:
>
>> "Eeysore Fucking Pommy IDIOT "
>> >
>> > Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>>
>> ** NOT AGAIN !!!
>>
>> Can't the Graham Stevenson MORON ever get a
>>
>> FUCKING decimal point right ?????
>>
>> Or any other point right ??
>
>It's that damn Windows calculator !
---
A poor workman blames his tools.
--
JF
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Author: John LarkinDate: 20:19 07-06-07
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On Fri, 8 Jun 2007 08:13:34 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:
>
>"Andrew Holme"
>>
>> Transmission line effects are negligible if the line length is a tiny
>> fraction of a wavelength.
>>
>
>** WRONG !!
>
Why?
John
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Author: Phil AllisonDate: 01:20 08-06-07
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"John Fields"
> A poor workman blames his tools.
** However, in this case the man's " tool " is clearly the problem.
....... Phil
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Author: JasenDate: 05:00 08-06-07
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On 2007-06-07, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>
> skyline1@net.hr wrote:
>
>> (example: If we connect high power audio amp to speaker we don't have
>> to worry about the characteristic impedance of the cable) Can
>> somebody explain this?
>
> Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
??? how do you get that? I get 10km for free space so probably 5 or 6
km for twisted pair - what propagation rate does a twisted-pair give?
--
Bye.
Jasen
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Can someone recommend me a good book about that topic or a web site!
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Author: John LarkinDate: 13:37 08-06-07
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On 8 Jun 2007 09:00:03 GMT, Jasen <jasen@free.net.nz> wrote:
>On 2007-06-07, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>>
>>
>> skyline1@net.hr wrote:
>>
>>> (example: If we connect high power audio amp to speaker we don't have
>>> to worry about the characteristic impedance of the cable) Can
>>> somebody explain this?
>>
>> Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>
>??? how do you get that? I get 10km for free space so probably 5 or 6
>km for twisted pair - what propagation rate does a twisted-pair give?
I'd vote for 15 km.
Figure twisted pair at roughly 0.7, depending.
John
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Author: EeyoreDate: 13:59 08-06-07
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Jasen wrote:
> Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
> > skyline1@net.hr wrote:
> >
> >> (example: If we connect high power audio amp to speaker we don't have
> >> to worry about the characteristic impedance of the cable) Can
> >> somebody explain this?
> >
> > Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>
> ??? how do you get that? I get 10km for free space so probably 5 or 6
> km for twisted pair - what propagation rate does a twisted-pair give?
I get it using the MS calculator which I find very easy to accidentally move the
decimal point one place.
Graham
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Author: Rich GriseDate: 14:15 08-06-07
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On Thu, 07 Jun 2007 17:19:19 -0700, John Larkin wrote:
> On Fri, 8 Jun 2007 08:13:34 +1000, "Phil Allison"
<philallison@tpg.com.au>
>>"Andrew Holme"
>>>
>>> Transmission line effects are negligible if the line length is a tiny
>>> fraction of a wavelength.
>>>
>>** WRONG !!
>>
> Why?
Because in Phil's universe, everything is wrong? ;-)
Cheers!
Rich
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Author: Rich GriseDate: 14:18 08-06-07
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On Fri, 08 Jun 2007 17:59:45 +0000, Eeyore wrote:
> Jasen wrote:
>> Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>> > skyline1@net.hr wrote:
>> >
>> >> (example: If we connect high power audio amp to speaker we don't have
>> >> to worry about the characteristic impedance of the cable) Can
>> >> somebody explain this?
>> >
>> > Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>>
>> ??? how do you get that? I get 10km for free space so probably 5 or 6
>> km for twisted pair - what propagation rate does a twisted-pair give?
>
> I get it using the MS calculator which I find very easy to accidentally
> move the decimal point one place.
It's lame to blame the calculator. Man up, say, "I made a mistake", and
get on with your life.
Cheers!
Rich
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Author: John LarkinDate: 20:55 08-06-07
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On Fri, 08 Jun 2007 18:15:42 GMT, Rich Grise <rich@example.net> wrote:
>On Thu, 07 Jun 2007 17:19:19 -0700, John Larkin wrote:
>> On Fri, 8 Jun 2007 08:13:34 +1000, "Phil Allison"
<philallison@tpg.com.au>
>>>"Andrew Holme"
>>>>
>>>> Transmission line effects are negligible if the line length is a tiny
>>>> fraction of a wavelength.
>>>>
>>>** WRONG !!
>>>
>> Why?
>
>Because in Phil's universe, everything is wrong? ;-)
>
>Cheers!
>Rich
umm, good point.
John
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